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PIN]???a ’ Q-‘ 'I‘- ‘ i' ”‘I'I‘J‘I I ':V’ ‘V IIII‘ I‘6 ‘ I 1,11\‘I 5‘1“5"J.l ‘ llllllllIllll‘llllllllllllll‘mll w 3 12 3 00632 6734 This is to certify that the thesis entitled ENERGY REQUIREMENTS OF COWS AND THE EFFECT OF SEX, SELECTION, OF CALVES OF FOUR GENETIC TYPES presented by Harold William Harpster has been accepted towards fulfillment of the requirements for Ph.D. degree in Animal Husbandry 57/27/75 / / 0-7 639 FRAME SIZE, AND ENERGY LEVEL ON PERFORMANCE L I B R A R Y Michigan State University ~' hike»: ,..> ’9‘ _ _l ENERGY REQUIREMENTS OF CONS AND THE EFFECT OF SEX, SELECTION, FRAME SIZE, AND ENERGY LEVEL ON PERFORMANCE OF CALVES OF FOUR GENETIC TYPES By Harold William Harpster A DISSERTATION Submitted to . Michigan State Univer51ty‘ in partial fulfillment of the requ1rements for the degree of DOCTOR OF PHILOSOPHY Department of Animal Husbandry 1978 Gf/Qéég ABSTRACT ENERGY REQUIREMENTS OF COWS AND THE EFFECT OF SEX, SELECTION, FRAME SIZE, AND ENERGY LEVEL ON PERFORMANCE OF CALVES OF FOUR GENETIC TYPES By Harold William Harpster Cow-Calf Trials Two cow-calf trials were conducted to examine the adequacy of energy levels recommended by the National Research Council (NRC) for cows of varying mature sizes and genetic backgrounds when maintained in unsheltered northern climatic conditions. Ten pregnant cows per cattle type were used in each trial. Types included: Unselected Hereford (USH), Selected Hereford (SH), Angus x Hereford x Charolais crossbred (AHC), and Angus x Hereford x Holstein crossbred (AHH). Body weights were recorded monthly and body condition was assessed by ultra- sonic evaluation of external fat. Based on the two levels of energy fed, NRC recommendations were at least 25% too low for all types of cows maintained under harsh climatic conditions. Increasing the energy level fed to cows was not accompanied by increased efficiency to weaning (total TDN intake/calf weaning weight). However, rebreeding performance 0f the cows must be considered and was unacceptable for cows fed in trial T. In both trials, the larger framed AHC and AHH cows were more efficient to weaning (TDN/calf weaning weight) than the smaller framed USH and SH types. ...,ng' Harold William Harpster Metabolism Trials Two total collection balance trials were conducted to compare the nitrogen and energy utilization of cattle of four genetic types when fed high corn silage (HS) or 80% concentrate high grain (HG) rations. Two growing steers per type (USH, SH, AHC, and AHH) received each ration in each trial. Digestibility, nitrogen retention and metabolizable energy values of the rations did not differ among the cattle types. Net protein (percentage of nitrogen intake retained) and metabolizable energy (Mcal/kg) values for the HS and HG rations were 24.2, 2.58 and 32.6, 2.96, respectively. Feeding Trials: Steers and Heifers The feedlot performance and carcass characteristics of 56 steer and 57 heifer calves of the four genetic types (USH, SH, AHC, and AHH) were compared (two trials). All cattle were fed a high silage ration and initial and final body composition data were obtained. Steers gained l9% faster than heifers and tended to be more efficient although feed/gain differences were small when adjusted to similar carcass fat. Carcass quality was similar when steers and heifers were compared at similar total carcass fat. Metabolizable energy required for carcass energy gain and edible portion produced were l0 and 5% greater for heifers, respectively, when both were compared at 29.2% carcass fat. Feeding Trials: High Silage and High Grain Steers The influence of energy level and cattle type on the feedlot performance and carcass characteristics of 87 steers fed high silage Harold William Harpster (HS) and 89 steers fed 7l% concentrate high grain (HG) rations was examined (three trials). USH, SH, AHC, and AHH cattle types were fed in each trial. Daily carcass protein and fat gain were 30 and 25% greater, respectively, for steers fed HG. When carcass characteristics were adjusted to the same hot carcass weight within a cattle type, differences in quality grade were small. Metabolizable energy required per unit edible portion produced was 4% higher for steers fed HS and was attributed to a higher proportion of ME available for productive purposes. The primary effect of selecting for yearling weight was to increase frame size. Daily gains of USH, SH, and AHC steers were consistent with expectations based on frame size while AHH steers gained at less than expected rates. Relative dry matter intake (g/Wkgs) was similar for all cattle types and less than predicted for AHH steers. Carcass quality of AHH steers compared favorably to the other types when all were compared at 32.3% carcass fat. Feed required per unit gain decreased with decreasing frame size. AHH steers were less efficient in converting ration protein and energy to carcass gain. ACKNOWLEDGMENTS Sincere appreciation and gratitude is expressed to the author's major professor, Dr. Danny G. Fox, for his expert advice, guidance, and encouragement during the graduate program. The knowledge and friendship gained through association with Dr. Fox will always be treasured. Appreciation is expressed to the Animal Husbandry Department of Michigan State University, Dr. Ronald H. Nelson, Chairman, for facilities, research animals, and financial assistance. Appreciation is further extended to Dr. Nelson for serving as a member of the graduate committee. The author wishes to thank the entire staff and faculty of the Animal Husbandry Department for their cooperation and help throughout the graduate program. The author is grateful to the other members of his Graduate Committee: Dr. Werner G. Bergen, Dr. William T. Magee and Dr. Harlan D. Ritchie, Animal Husbandry Department; Dr. J. Roy Black, Agricultural Economics Department; and Dr. John T. Huber, Dairy Science Department. Their advice and critical review of the dissertation is deeply appreciated. Special thanks are further extended to Drs. Black and Magee for help in statistical analysis of the data. The author is grateful to Dr. Roger Crickenberger for SUPPTYTDQ feedlot data which was incorporated into the dissertation. AppreCiation is extended to Elaine Fink for aid in laboratory analysis and to the graduate students of the Animal Husbandry Department for assistance in management of the experimental animals. Thanks are extended to. Dr. J. H. Britt, Dairy Science Department, for DGIP 1” the rebreeding experiment and analysis of blood samples. Special appreciation is expressed to the Department of Dairy and Animal Science of The Pennsylvania State UniverSity, Dr. B. R. Baumgardt, Head, for granting educational leave enabling the autho to pursue the graduate program. Sincere thanks are expressed to Mrs. Grace Rutherford for her excellent typing of this manuscript. Above all, deepest love, appreciation, and gratitude TS expressed to the author's wife, Dawn, and daughter, Lisa Marie, for their sacrifices, help, and support throughout the graduate t Program. Special thanks are also extended to the author 5 paren sPse W20$e continued encouragement has meant so much throughout the cou 0 studV. ¥ TABLE OF CONTENTS LIST OF TABLES .......................... LIST OF FIGURES ......................... INTRODUCTION ........................... LITERATURE REVIEW ........................ Effect of Cattle Type and Energy Level on Cow-Calf Performance ........................ Productivity to Weaning ................. Impact of Environment .................. Conception to Slaughter Analysis ............. Performance of Feedlot Cattle ................ Effect of Cattle Type on Nutrient Requirements and Utilization ...................... Impact of Cattle Type on Growth and Fattening Potential ....................... Growth and Carcass Characteristics of Feedlot Heifers Influence of Cattle Type and Ration Energy Level on Feedlot Performance and Carcass Characteristics OBJECTIVES ............................ MATERIALS AND METHODS ...................... Cow-Calf Trials ....................... Source and Genetic Background of Experimental Animals . . Experimental Design and Rations ............. Management Procedures .................. Metabolism Studies ...................... Experimental Animals ................... Trial Design, Rations, and Collection Procedures ..... Laboratory Analyses ................... Calculations ....................... Feedlot and Body Composition Studies ............. Experimental Animals ................... Trial Design and Rations ................. Management Procedures .................. 1'11 (1) (A) I'\3—-‘ ( (‘1 ‘A - -- -- -‘ Initial Slaughter Animals ................ 9 Final Slaughter Procedure and Carcass Evaluation ..... 9 Procedures for Determining Body Composition ....... 9 Carcass Performance Calculations ............. 9 Economic Analysis .................... 9 Analysis of Data ....................... 9 General Statistical Procedures .............. 9 Cow-Calf Trials ..................... lO Metabolism Studies .................... lO Feedlot and Body Composition Studies ........... l0 RESULTS ............................. lO Cow-Calf Trial 1 ....................... l0 Weight and Condition of Cows ............... lO Preweaning Calf Performance ............... l0 Cow Intake and Efficiency of Producing Calf Weaning Weight ..................... lO Rebreeding Performance .................. ll Cow-Calf Trial 2 ....................... ll Weight and Condition of Cows ............... ll Preweaning Calf Performance ............... ll Cow Intake and Efficiency of Producing Calf Weaning Weight ..................... ll Metabolism Studies ...................... l2 Nitrogen Utilization ................... l2 Energy Utilization .................... l2 Feeding Trials: Steers y§_Heifers .............. l2 Initial Slaughter Cattle ................. l2 Intake, Gain, and Feed Efficiency ............ 12 Carcass Characteristics ................. 12 Composition of Carcass Gain ............... 13 Efficiency of Carcass Production ............. )3 Economics ........................ T3 Feeding Trials: High Silage y§_High Grain Steers ...... 13 Initial Slaughter Cattle ................. 13 Intake, Gain, and Feed Efficiency ............ T3 Carcass Characteristics ................. 14 Composition of Carcass Gain ............... 14 Efficiency of Carcass Production ............. T4 Economics ........................ 14 DISCUSSION ............................ 15 Cow-Calf Trials ....................... l5 Energy Requirements ................... lE Preweaning Calf Performance ............... l5 iv Efficiency of Production ................. Metabolism Studies ...................... Nitrogen Utilization ................... Energy Utilization .................... Feeding Trials: Steers y§_Heifers .............. Intake, Gain, and Feed Efficiency ............ Carcass Characteristics ................. Composition and Efficiency of Carcass Gain ........ Economics ........................ Feeding Trials: High Silage y§_High Grain Steers ...... Intake, Gain, and Feed Efficiency ............ Carcass Characteristics ................. Composition and Efficiency of Carcass Gain ........ Economics ........................ CONCLUSIONS ........................... APPENDIX ............................. LITERATURE CITED ......................... Pa LIST OF TABLES Table l. Efficiency of Beef Production Among Breeds ........ 2. Efficiency of Production of 2-Year-Old Hereford, Hereford x Holstein, and Holstein Cows .......... 3. Experimental Design of Cow-Calf Trials (Trials l, 2) . . . 4. Rations Fed to Unselected Hereford, Selected Hereford, Angus x Hereford x Charolais, and Angus x Hereford x Holstein Steers in Metabolism Studies (Trials 1, 2) 5. Experimental Design and Rations for Feedlot Trial 1 6. Nutrient Composition of Ration Ingredients for Feedlot Trial l ......................... 7. Experimental Design and Rations for Feedlot Trial 2 8. Nutrient Composition of Ration Ingredients for Feedlot Trial 2 ......................... 9. Experimental Design and Rations for Feedlot Trial 3 l0. Nutrient Composition of Ration Ingredients for Feedlot Trial 3 ......................... ll. Procedures and Equations for Determining Carcass Composition and Performance ............... l2. Effect of Cattle Type on Cow and Calf Performance (Trial l) ........................ 13. Mean Daily Dry Matter and Total Digestible Nutrient Intake of Trial 1 Cows and Efficiency of Feed Utilization for Production of Calf Weaning Weight l4. Rebreeding Data for Trial 1 Cows ............. l5. Effect of Cattle Type and Energy Level on Cow and Calf Performance (Trial 2) ................ vi Table 16. Mean Daily Dry Matter and Total Digestible Nutrient Intake of Cows Fed Two Levels of Energy and Efficiency of Feed Utilization for Production of Calf Weaning Weight (Trial 2) ................... l7. Effect of Cattle Type and Ration Energy Level on Utilization of Nitrogen by Metabolism Trial Steers . . . . 18. Effect of Cattle Type and Ration Energy Level on Utilization of Energy by Metabolism Trial Steers ..... l9. Shrunk Weights, Carcass Weights, and Carcass Composition of Initial Slaughter Cattle (Trials l, 2, 3) . . ..... 20. Effect of Sex on Intake, Gain, and Feed Efficiency of Steers and Heifers Fed a High Silage Ration ....... 2l. Effects of Sex on Carcass Traits of Steers and Heifers Fed a High Silage Ration When Cattle Were Adjusted to Similar Carcass Fat ................... 222. Effect of Sex on Carcass Gains and Energy Deposition of Steers and Heifers Fed a High Silage Ration . ..... 223. Effect of Sex on Metabolizable Energy Intake, Carcass Energy Gain, and Energetic Efficiency of Steers and Heifers Fed a High Silage Ration ............ 24L Effect of Sex on Daily Crude Protein Intake and Efficiency of Protein Utilization for Carcass Protein Production of Steers and Heifers Fed a High Silage Ration . . ........................ 235. Effect of Sex on Daily Edible Portion Gained and Efficiency of Energy Utilization for Edible Portion Production of Steers and Heifers Fed a High Silage Ration . . ...................... 226. Nonfeed Costs for Small, Average, and Large Frame Cattle .......................... 337. Feed and Nonfeed Costs for Steers and Heifers Fed a High Silage Ration .................... 28. Effect of Cattle Type and Ration Energy Level on Intake, Gain, and Feed Efficiency of Steers ........... Table 29. Effect of Cattle Type and Ration Energy Level on Carcass Characteristics When Steers Within Type Were Adjusted to Similar Carcass Weights ......... 30. Effect of Cattle Type and Ration Energy Level on Carcass Characteristics When Steers Were Adjusted to Similar Carcass Fat .................. 3l. Effect of Cattle Type and Ration Energy Level on Carcass Gain and Energy Deposition of Steers ....... 32. Effect of Cattle Type and Ration Energy Level on Metabolizable Energy Intake, Carcass Energy Gain, and Energetic Efficiency of Steers . . .......... 33. Effect of Cattle Type and Ration Energy Level on Daily Crude Protein Intake and Efficiency of Protein Utilization for Carcass Protein Production of Steers . . . 34. Effect of Cattle Type and Ration Energy Level on Daily Edible Portion Gained and Efficiency of Energy Utilization for Edible Portion Production of Steers 35. Feed and Nonfeed Costs for Steers Fed High Silage and High Grain Rations . . . . ............... 36. Comparative Gains of Heifers and Steers ......... l\.l Individual Weight and Condition Data for Unselected and Selected Hereford Cows and Calves (Trial l) ..... l\.2 Individual Weight and Condition Data for Angus x Hereford x Charolais and Angus x Hereford x Holstein Cows and Calves (Trial l) ................ l\.3 Individual Weight and Condition Data for Unselected and Selected Hereford Cows and Calves (Trial 2) ..... l\.4 Individual Weight and Condition Data for Angus x Hereford x Charolais and Angus x Hereford x Holstein Cows and Calves (Trial 2) ................ -l\.5 Climatic Conditions During Cow-Calf Trials (Trials l and 2 .......................... A.6 Individual Nitrogen Balance Data for Steers Fed High Corn Silage and High Grain Rations (Trial l) ....... viii Table A.7 Individual Energy Intake, Losses, Digestibility and Metabolizability Data for Steers Fed High Corn Silage and High Grain Rations (Trial l) ............. A.8 Individual Nitrogen Balance Data for Steers Fed High Corn Silage and High Grain Rations (Trial 2) ....... A.9 Individual Energy Intake, Losses, Digestibility and Metabolizability Data for Steers Fed High Corn Silage and High Grain Rations (Trial 2) ............. A.lO Genetic Background of Steers, Daily Intakes of Dry Matter (DM), Metabolizable Energy (ME) and Crude Protein (CP), and Efficiency of ME and CP Utilization for Carcass Production (Trial 1) ............. A.ll Individual Shrunk Weights and Carcass Characteristics of Unselected Hereford Steers (Trial l) . . . . ..... A. l2 Individual Shrunk Weights and Carcass Characteristics of Selected Hereford Steers (Trial 1) .......... A. l3 Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Charolais Steers (Trial l) ..... .A- 14 Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Holstein Steers (Trial l) ..... l\- l5 Individual Carcass Weight, Protein and Fat Data for Unselected Hereford Steers (Trial l) ...... . . . . l\. l6 Individual Carcass Weight, Protein and Fat Data for Selected Hereford Steers (Trial 1) . ....... I). l7 Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Charolais Steers (Trial 1) ...... l)- l8 Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Holstein Steers (Trial l) ..... ’\~ 19 Genetic Background of Heifers and Steers, Daily Intakes of Dry Matter (DM), Metabolizable Energy (ME) and Crude Protein (CP), and Efficiency of ME and CP Utilization for Carcass Production (Trial 2) ............. A.20 Individual Shrunk Weights and Carcass Characteristics of Unselected and Selected Hereford Heifers (Trial 2) Table A.2l A.22 A.23 A.25 A.26 A.27 A.28 A.29 A.30 A.3l A.32 A.33 A.34 Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Charolais and Angus x Hereford x Holstein Heifers (Trial 2) ................ Individual Shrunk Weights and Carcass Characteristics of Unselected Hereford Steers (Trial 2) ......... Individual Shrunk Weights and Carcass Characteristics of Selected Hereford Steers (Trial 2) .......... Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Charolais Steers (Trial 2) ..... Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Holstein Steers (Trial 2) ..... Individual Carcass Weight, Protein and Fat Data for Unselected and Selected Hereford Heifers (Trial 2) . . . . Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Charolais and Angus x Hereford x Holstein Heifers (Trial 2) ................ Individual Carcass Weight, Protein and Fat Data for Unselected Hereford Steers (Trial 2) ........... Individual Carcass Weight, Protein and Fat Data for Selected Hereford Steers (Trial 2) ............ Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Charolais Steers (Trial 2) ...... Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Holstein Steers (Trial 2) . . ..... Genetic Background of Heifers and Steers, Daily Intakes of Dry Matter (DM), Metabolizable Energy (ME) and Crude Protein (CP), and Efficiency of ME and CP Utilization for Carcass Production (Trial 3) ............. Individual Shrunk Weights and Carcass Characteristics of Unselected and Selected Hereford Heifers (Trial 3) Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Charolais and Angus x Hereford X Holstein Heifers (Trial 3) ........... . Page 200 20l 202 203 204 205 206 207 208 209 210 2ll 212 213 Table A.35 A.37 A.38 A.39 A.4O A.41 A.42 A.43 A.44 Individual Shrunk Weights and Carcass Characteristics of Unselected Hereford Steers (Trial 3) ......... Individual Shrunk Weights and Carcass Characteristics of Selected Hereford Steers (Trial 3) .......... Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Charolais Steers (Trial 3) ..... Individual Shrunk Weights and Carcass Characteristics of Angus x Hereford x Holstein Steers (Trial 3) ..... Individual Carcass Weight, Protein and Fat Data for Unselected and Selected Hereford Heifers (Trial 3) . . . . Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Charolais and Angus x Hereford x Holstein Heifers (Trial 3) .............. Individual Carcass Weight, Protein and Fat Data for Unselected Hereford Steers (Trial 3 . . . ........ Individual Carcass Weight, Protein and Fat Data for Selected Hereford Steers (Trial 3) ............ Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Charolais Steers (Trial 3) ...... Individual Carcass Weight, Protein and Fat Data for Angus x Hereford x Holstein Steers (Trial 3) ....... xi Page 214 215 216 217 218 219 220 221 222 223 LIST OF FIGURES Figure 1. Mean weight and external fat changes of Unselected Hereford, Selected Hereford, Angus x Hereford x Charolais, and Angus x Hereford x Holstein cows (trial 1) ....................... 2. Mean weight and external fat changes of trial 2 Unselected Hereford cows fed two levels of energy . . . . . . . . ................. 3. Mean weight and external fat changes of trial 2 Selected Hereford cows fed two levels of energy 4. Mean weight and external fat changes of trial 2 Angus x Hereford x Charolais cows fed two levels of energy ....................... 5. Mean weight and external fat changes of trial 2 Angus x Hereford x Holstein cows fed two levels of energy ..................... INTRODUCTION Crossbreeding, selection programs, the role of the feedlot heifer, and the use of dairy breeding in beef production are topics of continuing interest to those concerned with the beef industry. Complete evaluation of these various types of cattle require analysis of both the cow—calf and feedlot phases of production. From a total industry perspective, the advantage of certain breeds or types in one phase may be offset in another phase. Dairy or dairy x beef breeds of cows typically produce more milk, are superior in lactation efficiency, and wean heavier calves than straightbred beef breeds. However, cattle of dairy breeding background may be less efficient in producing feedlot gain (Dean §t_al,, 1976). Additionally, while cows of larger mature size typically wean heavier calves than cows of smaller mature size, the added cost of maintaining the heavier cows must be charged against the increased calf weight obtained. Selection programs have generally emphasized growth rate; faster growing animals of larger mature size have resulted. Thus, the efficiency of production of large vs small cattle types is of considerable interest. While relatively high heritability estimates fm‘feed efficiency have been reported, in most studies it is unclear MEther aninmls were compared at similar finish since carcass fat was notmeasured. Such heritabilities would have been overestimated if the more efficient animals were those that had gained faster but were killed at an earlier stage of growth. Few experiments have been conducted to examine the efficiency of selected vs unselected individuals originating from a common genetic base. The assumption that larger animals are energetically more efficient than smaller types is not well founded if the animals are compared over similar initial and final body composition (Fox and Black, 1977). Numerous studies have compared large and small straightbred British breed cattle with British x Exotic and British x dairy breed crosses. Further work is needed, however, in which these types originate from a common genetic base and are compared at similar final composition. Economic conditions prevailing in the cow-calf phase of production typically dictate that feed and shelter inputs be kept to a minimum. However, field observation have indicated that many cows wintered without shelter in harsh northern climates were of poor condition when fed levels of energy recommended by the National Research Council (NRC, 1970, 1976). Sufficient feed inputs are needed to insure acceptable preweaning calf performance and rebreeding of the cow. FEW studies have examined the adequacy of NRC recommendations under harsh dimatic conditions for cows of varying mature size and QGHEtIC background. LITERATURE REVIEW Effect of Cattle Type and Energy Level on Cow—Calf Performance The beef cattle industry is characterized largely by segmented phases of production. Traits of great significance to the cow—calf producer such as fertility, longevity, and milk production may be of little direct importance to the feedlot operator who is more concerned with postweaning daily gains and efficiency of gain. Obviously, from a total industry perspective, both phases of production must be con- sidered in complete evaluations of various cattle types. As pointed °Ut by Gregory (1972), there has been a tendency in the past to extrapolate the results of only the growing-finishing segment of Production to the entire life cycle efficiencies of various cattle tYpes. The dangers of such conclusions are obvious when it is noted that only 35% of the total (cow + calf) nutrients required to market a 1,000 lb steer are consumed during the feedlot phase (Gregory, 1972). While the intended market dictates, at least to a certain extent, the amount of external fat or condition required in the feed— lot market animal, the amount of condition desirable in the breeding animal is rather arbitrary. Most would agree only that cows should be 0f “sufficient” condition to wean a calf of ”acceptable" weight eVery 12 months. However, the level of inPUts desirable may vary With cattle type, ration, climate, and economic conditions. This section will deal with the effect of such factors on the efficiency of cow—calf production. The final topic will include consideration of the feedlot phase and briefly summarizes studies which have examined cattle type differences in efficiency from ”conception to slaughter.” Productivity to Weaning The efficiency of beef production to weaning is of considerable interest since the industry carries two animals in the breeding herd for each animal going to slaughter (Cartwright, 1970). However, carefully designed and conducted studies are more rare in the literature than postweaning performance trials, likely due to the special problems encountered in cow-calf research. While typical feedlot conditions are relatively easy to duplicate, the same cannot be said for the cow herd where reliable measurement of feed intake typically requires the con— finement of cows. Cattle type or energy level effects on rePY‘OdUCtIVe Performance will normally require large numbers and several years of observations. Cows which abort, fail to conceive, or lose their calf Prior to weaning play havoc with experimental design and require the substitution of a replacement animal or statistical analysis with missing data. Also variation in time of calving within and between treatments may influence the factors being studied. Further obser— vations on the problems of data analyses may be found in Jordan 23.91- (1977). The relationship of cattle type and efficiency inevitably involves the significance of cow size. Klosterman (1972) has p01"t8d L out that many problems confronting the cattle industry are of more importance than how big cattle should be. These include: feed efficiency, calving percentage, and type as related to carcass characteristics. Increasing biological efficiency of cow-calf production by selection for a given body size is likely futile. If maintenance requirements and feed consumption are related to some fractional power of body weight (Kleiber, 1961), a size advantage in efficiency of production could be expected only if intrinsic efficiencies differ. Kleiber (1947) has stated that genetic variation dependent on body weight is irrelevant in any selection program for efficiency of production. Reliable studies relating cow size to productivity are rather rare due to the large numbers and long periods of time required for meaningful conclusions. Knox (1957) compared compact and large type Hereford cows. Lifetime production values for calves weaned per year were 75.2% for compact and 92.5% for the large types. Weaning weights were 170 and 182 kg, respectively. A combination of these results indicated a 32% advantage of the large type cows in total calf weight weaned. Nelson and Cartwright (1967) found a negative relationship between fertility and calf preweaning average daily gain (1,052 Angus and Hereford COW-calf pairs). A nonlinear relationship 0f COW weight and calf growth rate was indicated as intermediate weights of cows (570 kg for Angus and 600 kg for Hereford) gave maximal Preweanw average daily gain of progeny. L Hawkins _t_al, (1965) studies 919 calving records from 214 Hereford cows. Cows with heaviest precalving weights had fewer calves born and/or weaned per cow mated and lower 205—day weaning weights. Conversely, cows weighing less at weaning time weaned more calves and a larger total weight of calves than heavier cows. While a small degree of heterosis is noted in mature weight of cattle (Cundiff, 1970), it is highly responsive to selection. Brinks §t_gl. (1962) presented a heritability estimate of approximately 0.60 for mature weight in Hereford range cows. Several thousand cow—calf records were analyzed covering a time span of 33 years. Small cor- relations were found between cow and calf weights with some indication of heavier cows producing heavier, faster gaining calves. Increases in cow weights over winter were also positively associated with faster gaining calves. However, increases in cow weight during lactation were negatively correlated with calves' weights and gains. Both results are consistent with several subsequent short-term studies (Jordan gt_al., 1977; Hironaka and Peters, 1969). Klosterman _t__l. (1968a) compared the Hereford and Charolais breeds and their crosses under two systems of management. Three calf crops were produced by each of approximately 50 Hereford and 50 Charolais cows. Cows were bred to produce equal numbers of Hereford, Charolais and crossbred calves. Half the calves were creep fed and placed in the feedlot after weaning, the other half were not creep fed, wintered to gain 0 5-0.6 kg daily, grazed, and then placed in the feedlot. Records were available for 205 straightbred and 109 L crossbred cows. Calves born as a percentage of cows bred was 86% for straightbred and 89% for crossbred. Values for calves weaned as a percentage of cows bred were 76 and 77% for straightbred and crossbred cows,. respectively. Birth weights, 260 day weaning weights, and daily gains to weaning were (lb) 70, 518, 1.58; 83, 645, 1.99: and 77, 602, 1.85 for Hereford, Charolais, and crossbred calves, respectively. These data were adjusted for differences among years, sex, and system of rnanagement. Small but consistent evidence of hybrid vigor for these traits were thus noted (1 to 4% advantage of crossbreds over average 0f straightbreds). Highly significant and positive relationships were found between weigght of cow and birth and weaning weight (within breed). Fertility was rmnzconsidered in that only cows with a weaned calf were included in the analysis. The total digestible nutrients supplied through creep feeding were about 10% of the total required to weaning and increased weaning weight an average 70 1b. Carpenter _t_al, (1971) found that Hereford and Hereford x Brahman crossbred cows with heavier mature weights weaned heavier calves. However, relative to lighter weight cows, they exhibited longer calving intervals and produced fewer calves per unit time. Straightbred Hereford (H) cows and calves were compared with Angus-Jersey (AJ) cows and their Charolais sired calves (Ellison gt_a1:, 1974). Weaning and yearling weights were similar while AJ cows gave birth to lighter calves (3-4 kg), produced more milk (+1.3 kg/day), and consumed less feed (-14.3%). Lindsey gt a1. (1970), using records from 67 Angus, Hereford, amd Shorthorn cows regressed weaning weight on cow weight/height ratio. An iintermediate optimal ratio of 4.5-5.0 kg/cm was reported. Visual conciition scores of cows were negatively associated with calf weaning weight. Carpenter et_al, (1972a) studied the performance of 30 Hereford and 15 Charolais cows fed to maintain a constant level of fatness. llware were no significant associations between cow size and milk yield Witifin breeds. Weight changes during the productive year and mature Size were not closely related. Production efficiency on the same cows (Carpenter £11., 1972b) was examined and defined as calf weaning weight per unit feed for the cow and calf. A trend for greater efficiency of smaller cows within a breed was noted, although the trend was reversed between breeds. Smith gt_al, (1976b) studied the gestation length, birth weight, d.Ystocia level, calf mortality, and preweaning growth of 2,368 calves out of Hereford and Angus cows and by Hereford, Angus, Jersey, South Devon, Limousin, Charolais and Simmental sires. Charolais and Simmental crosses had faster preweaning average daily gains but also larger birth weights and more dystocia. Jersey crosses were lightest at birth and experienced considerably less dystocia than other crosses. Preweaning relative growth rate (percent increase in body weight daily) was highest for Jersey and lowest for South Devon, Limousin, Charolais, and Simmental crosses. Hereford by Angus heterosis was significant for birth weight, daily gain, and calf survival. Past results from a continuing breeding project comparii genetic types have been presented by Magee and Greathouse (1969 1971, 1972, 1973); Magee (1974); and Magee and McPeake (1975, 1! The four breeding groups were established from a common source 1 grade Hereford cows. Groups included Unselected Hereford (USH). Selected Hereford (SH), Angus x Hereford x Charolais (AHC), and Angus x Hereford x Holstein (AHH). The mating system in the US} gratua was random while selection in the remaining groups was bas on yearling weight; sires were superior bulls from A1 studs. A rotational crossbreeding system was used in the AHC and AHH grOL McPeake (1977) summarized the results from the 1972 thrc 1976 <:a1f crops with the following conclusions relative to cow Productivity and preweaning performance: E1. Selection accounted for an 11.4% increase in actual wean weight. 1). Selection for yearling weight and crossbreeding increase cow weight. c. Selection did not improve fertility while crossbreeding improved fertility an average 7.7% over the SH group. d. Rotational crossbreeding increased adjusted weaning weig 13.1% and 21.4% in AHC and AHH groups, respectively. e. The additional milk received by nursing crossbred heifer may have reduced their productivity as cows. General effects of energy level and age of cow on rebree Parformance were presented by Hi 1tbank (1976): / 10 Level of feed In heat gy days Before After Age of after calv1ng calving calving fl g1 7_0 _99 High Moderate Mature 65 90 95 High Moderate Young 53 91 98 Low Moderate Mature 25 70 85 Low Moderate Young 28 68 87 It was stressed that to obtain equal response from young vs mature cows it would likely be necessary to separate the two age groups to insure adequate nutrient intake. Wiltbank (1976) presented data from 686 cows in which the effect 0f b0dy condition at calving on the onset of estrus was examined: Days after calving and % estrus Body go. 40 50 60 7o 80 9o condition cows (%) (%), (%) (%) .(%) (%) Thin 272 19 34 46 55 62 66 Moderate 364 21 45 61 79 88 92 Good 50 31 42 91 96 98 100 COWS were further classified as to calving time in four 20-day periods from December 20 to March 2. The 80-day breeding season extended from March 13 to June 11. In cows from the first three calving groups, 81% of the thin and 95% of the cows in good condition were pregnant after 80 days of breeding. HOwever, only 54% of the thin and 85% of the good cohdition cows from the fourth calving group became pregnant. Davis _e_t_ §_l_. (1977) studied the effect of winter nutrition on “Productive performance of Hereford cows of various ages. Three 2-year trials were conducted. Various combinations and amounts of 4 a——‘__ 11 soybean meal, sorghum grain, and alfalfa hay were fed to cows mai on dormant range over winter. Sorghum grain (1.4 kg/day) was sup to soybean meal (0.7 kg/day) in improving weaning weight and repr tion when fed with 1.4 kg alfalfa hay. Additionally, doubling th amount of sorghum grain increased performance. Thus, energy and protein was assumed limiting for reproduction. Delaying a portion of the winter feed until after calving decreased rebreeding performance in 2- and 3-year-old but not mat cows. Cows which rebred were generally those which lost less wei in winter and gained more weight in the subsequent grazing period Reproductive performance of Angus (A), Brahman (B), and Charolais (C) cattle was reported by Peacock g’ga_1_. (1977), in a Florida study. Cattle were straightbred and reciprocally crossed with an average of 121 matings over 11 years for each of the nine 90551 ble parent breed combinations. Pregnancy rate was described as Cows pregnant of cows exposed. Survival rate was expressed as the percentage of calves surviving to weaning of cows pregnant an wefining rate was calculated as the product of pregnancy and survi rates. Pregnancy rate was influenced by breed of sire with mean 01: 74.4, 82.3, and 79.1% for A, B, and C sires, respectively. Ca SuY‘vival was affected by breed of dam but not breed of sire (88.7 97.2, and 96.9% for A, B, and C dams, respectively). Weaning per was also affected by breed of dam (69.8, 76.5, and 75.9% for A, B C dams, respectively). A significant sire x dam interaction resu With C sire x A dam matings lowest (63.8%) and C sire x B dam mat 12 highest (82.2%) in weaning rate. These and other results caused the authors to conclude that large sire breeds crossed on small dam breeds may result in a net decrease for weaning rate. Bowden (1977) compared 29 Simmental x Angus (SA), 28 Charolais x Angus (CA), 25 Hereford x Angus (HA), and 25 Jersey x Angus (JA) fi rst-calf heifers for growth, reproductive performance, and feed utilization. All heifers were individually fed from 8 weeks postweaning until calving and were bred artificially to the same Red Poll bull. About 16 weeks after first breeding heifers were assigned to digestible energy (DE) levels sufficient for normal growth (based on mature size) or 110% of that level. Heifers fed at the latter level were heavier at calving. Body size measurements indicated the increased weight was due to additional soft tissue deposition and not skeletal growth. Total intakes of dry matter, DE and digestible protein were hiSher for SA and CA vs HA and JA heifers. Heifers fed at the high DE level gained 22% faster (0.50 kg/day) than those fed low DE (0.41). IWeeding performance did not differ significantly among the breed types 0" energy levels. Ultrasonically determined backfat depths (84 weeks 01’ age) did not differ by energy level and averaged 8 mm. The amount of DE used per unit metabolic wt for the duration of the trial differed Only slightly among the four types indicating similar relative requirements . The introduction of dairy breeding into the beef herd typically increases milk production and calf weaning weight (Deutscher and Whiteman, 1971; Holloway 331., 1975b; Wyatt etajp 1977c)- 13 However, the impacts of milk consumption and genetic backgrounc not been clearly delineated, since in most studies calves of si genetic composition consumed similar amounts of milk. Wyatt g1 (1977a) presented a study designed to examine the impact of eac Forty Hereford and 41 Holstein cows were bred to Angus Charolais bulls, respectively. One-half of the calves born to dams (A x H) were fostered onto Holstein cows and one-half of t born to Holstein dams (C x H) were reared by Hereford cows. Ea of calf thus received low milk (4.8 to 5.5 kg/day) and high mil 11.0 kg/day) levels. High milk increased weaning weight of dry calves 19 and 22% for A x H and C x H calves, respectively. At milk level, both types of calves consumed similar amounts (with 0.2 kg) of milk suggesting little effect of potential growth ra 0" milk intake. Increased milk intake was associated with decr intElke of creep feed. Theoretical energy requirements to produ Calf gain were calculated for Hereford and Holstein cows at hig (9.8 kg) and low (5.2 kg) levels of milk production. Megacalor 0T digestible energy (total cow + calf) required per kg calf ga "Ere 37.29 and 34.91 for low and high Herefords and 40.83 and 3 1:Or low and high Holsteins, respectively. As always, economic Siderations would dictate advisability of feeding for higher mi Production. A series of reports by Oklahoma workers compared the pe formance of Hereford, Hereford x Holstein, and Holstein cows as 2-year olds (Kropp £331., 1973); 3-year olds (Holloway $511., 1975a): and 4- and 5-year olds (Wyatt gt _a_1_., 1977c). Cows were maintained under both range and dry lot conditions. Three levels of winter supplement (30% protein range pellet) were fed. Moderate, High, and Very High levels were the amounts necessary to effect a weight loss from fall to spring of approximately 10-15% in Hereford, Crossbred, and Holstein cows, respectively. Moderate and High levels were fed to all three groups while only the Holsteins received the Very High level. Monthly weights and subjective condition scores were obtained. Milk production was estimated monthly by the weigh-suckle-weigh technique. Reproductive Performance was monitored. Though some year to year variations in relative performance of the cows at different ages existed, some consistent trends were evident. I“ dY‘y lot, increasing the level of supplement reduced winter weight 10$'Ses in Hereford and crossbred cows. Within the Holstein breed group, WEIth losses were not significantly different between the Moderate and High levels although Very High cows lost less weight than the other QFOUps. A11 cows except the Moderate and High Holsteins regained their winter losses during the summer months. Body condition scores 1"Ollowed weight change trends. Holsteins had lowest and Herefords hlghest condition scores in both dry lot and range cattle. Milk yields increased predictably with percentage Holstein breeding. In dry lot cows the level of winter supplement did not Effect the level of milk yield within breeds although yield tended to increase with increasing level of supplement. There were no 15 consistent effects of level of supplement on butterfat percentage within breed. Increased calf weaning weights were associated with level of inilk intake and percentage Holstein breeding, but additional feed was rwaquired to maintain the larger, heavier milking Holstein cows. Results 1~i th the 4- and 5-year old cows (Wyatt gt__l:, 1977c) revealed that Very Ftigh Holsteins consumed 3.4 times more winter supplement and 45% more forage than Moderate Herefords. Level of supplement had little effect on number of cows e>o uummo.o umwoo.o oomao.o oamacp.o onmmop.o aapmp.o nampp.o wpeo an oxaucw mo Poo: son poo: .uw mmaugou omapo.o oeepo.o oompo.o unempo.o unmopo.o nom.o.o namFo.o ePao so excuse me _moz can muau paced; ox ow.mom oom.nom ouue.am~ unm.cc~ uu~.m5~ am.nm~ a~.omm ox .u: mmmuteu . oucmscomcoa uopvwou opmo.o ammo.o ammo.o Nmmo.o ammo.o mNmo.o meo.o epeu can zoo xn oxapcm we a on on o u on on _moz Lon «game: mcwcmo: ax vam commm uomam comm comm awm_ noNF ax «swam: unease: .mmwceoz o» zucmquCCm o.mm N.~N m.m~ m.m~ n.- m.ep o.m_ cop x :ou e on a a a a sa easemeeo wa\me x_az aom.~ N.N.N omm.m unam.P comm.P aam—.P aNmF._ ox .coozuoga xpwe pouch expo.“ muco.n mam.o u_nm.m uommm.m on_mo.m nmmm.a poo: .corueuuop mcwgsc excuse me chomuwemo comumuoog ea_e sea> ems: opaeaeoz ems: ooaeoeaz new: doaeaeez soo_ :woumpoz umgammogu ucomogoz ucwEopnazm gouge: we po>m~ can women mzou smoumpoz was .cmopmpoz x ecomoso: .ucoemgoz tpo gmo>1~ co comuoauoga vo aocowowemm .N «pack 32 Performance of Feedlot Cattle Effect of Cattle Type on Nutrient Requirements and Utilization Possible cattle type differences in ability to consume feed, digestive powers, requirements for body functions, and intrinsic efficiency are of obvious interest. The difficulties in delineating the impact of some of these factors undoubtedly contribute to the small number of reports found in the literature. Reid (1962) concluded that animals differ mainly in the amount of feed they will consume and in the level of feed intake at which they form appreciable body fat. He found little animal variation in digestive powers and the efficiency with which ME consumed above maintenance is utilized. Thus, selection to improve efficiency should stress the former factors. The question of differing requirements for cattle of different size and weight but similar composition was addressed by Klosterman and Parker (1976). Weanling heifer calves (212 head) sired by Angus, Charolais, Jersey, and Brown Swiss bulls and out of Angus or Charolais dams were used in the 3-year study. One-half of each breed type (8 combinations) was fed at either 1.5 or 2.0 times their maintenance requirement where TDN for maintenance (kg) equals 0.030 Wkgs. The trial was continued for 210 days with rations adjusted based on bodyweights obtained every 14 days. Although initial weights and thus amounts of feed fed were significantly different among the various breed types, there were no significant differences among them in rate of gain. No significant interactions among breed types 33 and levels of feeding were noted in rate or efficiency of gain. Accurate measures of body composition were not made in this study. The authors speculated, however, that the larger type heifers were not expected to be, and did not appear to be, fatter at weaning. It was concluded that little justification existed for different energy requirements for gain of calves of different types. Stonaker gt_gl, (1952) compared the body size, gain, and efficiency of gain of large, intermediate, and comprest Hereford females 1wintered on hay. Highly significant differences were found for wither height measurements, average weight maintained, feed eaten daily, and daily gains. However, there were no differences in feed consumed per day per 1,000 lb of animal maintained or feed/gain. Since the pathways of intermediate metabolism for converting nutrients into lipid are probably very similar in all species of homoetherms and must be identical for individuals of the same species, the energy costs of fat deposition may be considered constant. The data of Garrett (1971), however, indicates at least the possibility that the efficiency of energy use for fat deposition may differ among Cattle of markedly different selection histories. Garrett (1971) compared the net efficiency of energy utilization for maintenance and energy gained by Holstein and Hereford steers in two trials. Voluntary intake per unit metabolic body size was higher for Holsteins in both trials. Maintenance requirements were 5 and 12% higher in Holstein steers for the two trials. In trial 1, production Per kg of feed consumed above maintenance was 24 g of protein and 115 g 34 of fat for Hereford y§_24 g of protein and 86 g of fat for Holsteins. Similar values for trial 2 were 30 g and 100 g for Herefords and 30 g and 87 g for Holsteins. The author cited his findings and evidence of other workers indicating similar energy costs for protein and fat deposition in a ruminant animal simultaneously synthesizing both. Thus, it was hypothesized that differences in energetic efficiency represented a true breed effect. The author did not attempt to identify, however, "the specific location in the complex scheme of energy metabolism at which the additional energy consumed by the Holsteins was wasted or lost." Blaxter and Wainman (1966) determined the fasting metabolism of seven Ayrshire, two Ayrshire x Beef Shorthorn cross and eight Angus steers. Determinations were conducted at numerous times during growth on various animals. Ages during the experimental period ranged from 0.3 to 3.7 years and weights from 63 to 594 kg. Two Ayrshire steers were considerably younger and lighter in weight than the remaining cattle, thus data were summarized for cattle weighing over 300 kg. Mean fasting heat production for these animals were 90.4, 96.3, and 81.0 kcal/Wk;3 for Ayrshire, Ayrshire crossbred and Angus steers, respectively. Values for both Ayrshire groups were significantly higher than for the Angus steers. The proportion of the total energy loss from the body which arose from protein oxidation averaged 24.5% and did not differ by breed. Hashizume gt_§l, (1963) conducted a series of 3 balance trials with 12 Japanese Black and 18 Holstein non-pregnant dry cows. Rations 35 in different trials were various combinations of timothy hay, wild grass hay, rice bran, straw, and a concentrate mixture. Balance trials and heat production were determined during periods of fasting and feed- ing. Fasting heat production when lying was 51.5 and 73.1 kcal/Wk;5 for Japanese Black and Holstein cows, respectively. Heat production values during feeding were 89 to 108 in Japanese Black and 107 to 130 kcal/Wl'é5 in Holstein cows. Calculated ME values for maintenance were 96 and 116 kcal/Wk;5 in Japanese Black and Holstein cows, respectively. Vercoe (1970) compared the fasting metabolism of Brahman, Africander, and Hereford x Shorthorn cattle (nine animals each). All animals were bulls except one Africander and three crossbreds which were steers. Three animals per breed were used in each of 3 years with mean ages of 22, 20, and 13 months (by year). Fasting metabolism values (kcal/Wkgs) were 86.4, 102.5, and 97.4 for the Brahman, Afri- cander, and crossbred steers, respectively. These findings were generally higher than similar values obtained by Blaxter and Wainman (1966) with steers. Several explanations were advanced for the higher estimates, the most likely thought to be the effect of intact bulls y; steers. It was stressed that a lower fasting metabolism of the Brahman cattle indicated either a lower requirement for energy to carry out the functions of basal metabolism (functions fewer or slower), or, assuming similar requirements, a more efficient use of the energy released by the biochemical processes occurring at basal conditions (less appears as heat). The second explanation was thought to be more likely. The lower heat production as an aid to thermal equilibrium in a hot environment was discussed. 36 In the previously cited review by Reid (1962), it was pointed out that considerable animal variation existed for the ability to consume feed and that selection for this trait would be of value. Several heritability estimates published in the literature tend to support this conclusion: Heritabiligy estimate Reference Details 0.43 Brown and Gacula, 1964 201 British breed bull calves 0.64 Koch gt_g1, 1963 1,324 British bull and heifer calves 0.07-0.77 Swiger gt_gl,, 1961 1,011 British breed bull and heifer calves 0.64 Swiger gt_gl,, 1965 480 British breeds and their crosses Bogart and England (1971) studied 290 British breed calves (bulls and heifers) of varying lines (three Hereford lines, one Angus line), years (6), and degrees of inbreeding (4 bulls from 0 to 21%+). A11 calves were individually fed gg_libitum to a constant final body- weight. Calves were weighed weekly and bedded with shavings. Conclu— sions were: (a) Heifer intakes per unit bodyweight were as high as those for bulls; (b) Lines differed in daily gain, feed consumption, and feed/gain; (c) Much of the variation in feed required per unit gain was accounted for by variations in daily gain and daily feed consumed; and (d) variation in feed intake was partly under genetic control with a heritability estimate of 0.38i:.15. In most experiments, little difference in digestive powers has been noted among cattle of varying breeds and types. Washburn 37 §t_gl, (1948) found no differences in DM digestibility of a mixed ration between compact and conventional Shorthorn steers. However, Ashton (1962) found that steers of Zebu background (Bos indicus) had sig- nificantly higher dry matter and apparent nitrogen digestibilities than steers of the Bos taurus species. Brahman, Hereford, and crosses of Brahman and Africander with Shorthorns and Herefords were compared on hay diets. Dry matter digestibilities were 56.0 and 53.3% for Brahman and Herefords, respectively. French (1940) observed a trend for greater digestibility in Zebu y§_Zebu-Ayrshire cattle but differences were not significant. Hungate §§_g1, (1960) found that the rumen fermentation rate per unit solids was greater in four Zebu y§_four ”mixed-breed European” cattle. A similar follow-up study was reported by Phillips §t_gl, (1960). Mean reticulo-rumen retention times (hr), dry matter digestibilities (%), and fermentation rates (u moles/g/hr) were: 37.3, 65, 145 and 34, 68, and 171 for European and Zebu cattle types, respectively. Karue gt_gl, (1972) compared Boran (a breed of Zebu type) and Hereford (75%) x Boran crossbred steers in a digestibility and nitrogen metabolism study. Trial 1 consisted of a low protein hay supplemented with vitamins and minerals. Coefficients of digesti- bility for DM, energy, and nitrogen were similar and not different although Boran steers consumed 23% more dry matter. Urinary nitrogen was significantly higher in the Boran steers. In trial 2 the low protein hay was supplemented with urea or cottonseed meal. Again, 38 coefficients of digestibility were similar and not different. Nitrogen retention was similar among breeds and differed only for supplemental nitrogen source. Howes §t_gl, (1963) compared the digestibility of a variety of feeds in Hereford and Brahman females. Pooled across rations, dry matter and crude protein digestibilities for Brahman y§_Hereford were 63 y§_61% and 50 y§_46%, respectively, although only the latter was significantly different. Moran and Vercoe (1972) reviewed a total of 107 digestibility trials comparing various Zebu and British breeds. They concluded that Zebus had lower metabolic fecal nitrogen and slightly higher true nitrogen digestibility than British breeds although differences were small. Reid (1962) concluded that the among-animal, within-feed variation in digestibility was so small that genetic improvement could not be expected in a reasonable period of time, even if the trait were heritable. Feed conversion (feed/gain), at a given stage of growth, is influenced by daily energy intake, energy requirements, and the effi- ciency of energy utilization. Because these factors interact in the feed/gain observed, interpretation of differences due to cattle type are difficult to make under comparable conditions. Further, little work has been done to delineate the impact of component parts of feed/gain among cattle types. Many comparisons of British and exotic breeds have shown more efficient live-weight gains for the latter in time constant trials 39 (National Academy of Science, 1975). Invariably, however, the larger type exotic cattle were leaner prohibiting examination of a true cattle type effect. Similar results were obtained in a comparison of British and Holstein steers (Bond g£_gl,, 1972). Two studies comparing British and Charolais steers to equal finish found no difference in feed effi- ciency (Klosterman gt_gl,, 1968a; Brungardt, 1972). Cundiff (1970) reported that heterosis for feed conversion was small and not significant. However, reasonably high heritability estimates have been reported in within-breed studies (Koch gt_gl,, 1963). In most cases, it is unclear, however, whether animals were compared at similar finish since carcass fat was not measured. Such heritabilities would have been overestimated if the more efficient animals were those that had gained faster but were killed at an earlier stage of growth. In addition, animals were fed gg_1ibitum in most trials, making it difficult to establish whether faster gaining animals simply consumed more energy above maintenance or were actually more efficient in conversion of ingested nutrients to body weight gain. However, from an economic point of view, it makes little difference which component of feed/gain is contributing to the increases observed. Impact of Cattle Type on Growth and Fattening Potential In understanding observed differences in quantity and type of growth among various cattle types, it is useful to review some of the basic differences encountered at the tissue and perhaps even cellular level. Studies relating these basic differences to types, strains, or 40 breeds of animals are unquestionably more numerous for rodents and pigs than for cattle. However, several examples can be found for the bovine specie and are briefly reviewed in this section. It is generally agreed that muscle cell hyperplasia is completed during fetal growth in meat animals (Joubert, 1956). Therefore, post— natal muscle growth is primarily the result of hypertrophy or increases in the size of the muscle fiber through synthesis of new protein. Normally, the maximum adult size of various cattle types is fixed at birth since differences in size between breeds within a species are due to differences in muscle cell number, not cell size (Hedrick, 1968). As pointed out subsequently, however, differences in cell size are noted in double muscled y§_normal cattle. The greater accretion of lean tissue mass by large y§_small type cattle is thus normally due to a greater number of muscle cells rather than increases in nucleic acids or efficiency of protein synthesis at the cellular level. While few studies have actually compared cattle type differences in ability to synthesize protein (cellular level), Ashmore and Robinson (1969) found similar muscle protein/DNA and RNA/DNA ratios in "double muscled" y§_ normal genotype cattle. Allen gt_gl, (1974) stressed the importance of examining changes in fiber type as well as size in assessing postnatal muscle growth. Genetic differences in proportions of anaerobic (white) and aerobic (red) fibers exist and relate to patterns of development, muscling, and meat quality, although cattle type comparisons have primarily involved double muscled yg normal cattle (Holmes and Ashmore, 41 1972; West, 1974). Anaerobic fibers apparently reach full growth potential later in life or at heavier body weights and delay the onset of the "fattening phase." Thus, from a fixed number of fibers, a larger muscle mass can be produced with a higher proportion of anaerobic fibers (Allen gt_gl,, 1974). Holmes and Ashmore (1972) found a higher conversion of aerobic to anaerobic fibers in double muscled y§_normal cattle. Anaerobic fibers were also larger than aerobic, reaching a greater final diameter. The significance of these observations in normal large y§_small type cattle has not been fully investigated. Guenther (1974) compared eight Angus and eight Charolais steers in a physiological maturity evaluation of the two breeds. Calves within breeds were from the same sire, were similar in age and were placed in the feedlot and fed a "standard finishing ration." Various body size measures, weights, and muscle biopsy samples were taken every 56 days for 8 consecutive sampling periods. Body weight and size measures were generally greater in the Charolais cattle for most periods. However, the Angus calves were greater in muscle fiber diameter for all periods reflecting an earlier maturation in fiber diameter. Numerous workers have examined type variations in fat depo- sition. Examples for the existence of genetic variation in composition and total quantity of lipids deposited include: (a) ruminants capable of hydrogenating dietary fats while monogastrics cannot; (b) double- muscled cattle which do not deposit fat as readily as those not exhibiting this trait; (c) breeds of sheep which accumulate greater ‘RM‘ .2_ 42 quantities of fat over the rump; and (d) lean and fat strains of pigs (Allen §§_gl,, 1976). Comparison of carcass characteristics among various cattle types will be more fully discussed in a subsequent section. However, basic differences in fat distribution among cattle types are noted here. Callow (1962) reported greater differences in percentage of fat in tissues of wholesale cuts attributable to breed than to nutritional level. In general, the dairy breeds appeared to have a higher propor- tion of kidney and pelvic fat and a smaller proportion of subcutaneous fat than beef breeds. Callow (1961) compared the carcass characteristics of Hereford, Shorthorn, and Friesian steers. Friesians had the highest proportion of fat in the body cavity and the lowest proportion in the subcutaneous depot. This pattern was reversed in the Hereford steers and inter- mediate in the Shorthorns. Cramer and Allen (1976) studied adipocyte development in the subcutaneous fat depots of Angus, Hereford, and Holstein calves from 36 to 538 days of age. Adipocyte diameter and volume were similar for all breeds. However, at the conclusion of the experiment, 12th rib fat thickness was 0.76 cm in Holstein and 1.55 cm in the Angus and Hereford breeds. Thus, the Holsteins apparently had fewer numbers of subcu— taneous adipocytes since cell sizes were similar. Hood and Allen (1973), however, reported fewer and smaller sized adipocytes in Holstein yg Hereford x Angus steers. 43 Biochemical evidence for cattle type differences in propensity to fatten exist, although results are variable. Acetyl-CoA carboxylase (CBX) appears to be the key regulatory enzyme in fatty acid synthesis in ruminants (Pothoven and Beitz, 1975). Chakrabarty and Romans (1972) found greater CBX activity per cell in the adipose tissues of beef y§_ dairy breed steers. Both types had higher activities in subcutaneous .yg intramuscular adipose, a result also noted in sheep by Parr (1973). Hood and Allen (1975) found higher CBX activity in the perirenal adipose tissue of 475 kg Holstien steers than in subcutaneous tissue. Similar activities were found in the two sites in Hereford x Angus steers of the same weight. Martin and Wilson (1974) determined activities of several lipogenic enzymes necessary for NADPH generation in five Hereford and seven Holstein steers. Steers were fed a 66% TDN diet gg_libitum from weaning to slaughter. Age and weight at slaughter was 397 and 357 days and 383 and 394 kg for Hereford and Holstein steers, respectively. Liver, brisket subcutaneous adipose, and perirenal adipose tissue samples were obtained at slaughter. Mean fat thickness between the 12th and 13th rib was 1.95 and 0.64 cm for Herefords and Holsteins, respectively. Overall, steers with greater adipose glucose 6-P04 dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD) levels gained at a slower rate and were fatter. Herefords were higher in subcutaneous 6PGD and perirenal adipose 6PGD and isocitrate dehy- drogenase. There were high negative correlations between these two enzymes and average daily gains. Similar observations on these enzymes 44 were reported by Hood and Allen (1975) in a comparison of Holstein and Angus x Hereford steers. Growth and Carcass Characteristics of Feedlot Heifers The analogy between performance differences due to sex and those due to frame size was discussed by Klosterman and Parker (1976). In support of this concept, the simulation model of Fox and Black (1977) predicts similar nutrient requirements, feed intake, and daily gains for small frame steers and average frame heifers (both expected to grade choice at 363-400 kg). Thus, differences in performance between steers and heifers are largely associated with physiological age or body compo- sition and not sex gg:_§g, Klosterman and Parker (1976) concluded from a summary of their work that differences in maintenance requirements among sizes, breeds, and sexes of cattle were relatively small. Bogart and England (1971) found similar intakes per unit body weight for heifers and bulls in a study of 290 British breed calves. Bose §t_gl, (1970) studied the comparative efficiency of Hereford bulls (10), steers (9), and heifers (11). Several nutritional treatments per sex were imposed, involving a low and high energy ration. Pooled results for average daily gains were 2.36, 1.70, and 1.55 and feed/gain values were 6.4, 8.4, and 9.2 for bulls, steers, and heifers, respectively. Initial and final body composition of steers and heifers was essentially the same. NEm and NEg values of the rations were (Meal/kg) 1.53, 1.14 and 1.51, 1.03 for steers and heifers, respectively. 45 Newland (1976) compared Angus steer and heifer calves finished to choice grade on either corn silage or whole shelled corn, each balanced with protein and minerals. Days on feed required to reach choice grade were 210 for steers and 183 for heifers fed all silage with gains of 2.25 and 1.90 lb per day, respectively. Similar values for the all concentrate ration were 154 days each and daily gains of 2.86 and 2.41 lb for steers and heifers, respectively. Feed/gain data were not available as steers and heifers were fed together. Ritchie g£_gl, (1977) found that when all heifers from a herd were compared to their steer mates, feed/gain values favored the heifers when both were compared at similar final composition. However, as noted by others (Klosterman and Parker, 1976; Cooper gt_§l,, 1972) heifers apparently had to be somewhat fatter than steers to achieve the same quality grade. Performance data for time-constant trials was presented by Wilson §$_g1, (1969). Data were collected from 80 steers and 94 heifers born from 1963 to 1966. Calves were the progeny of 11 different Polled Hereford bulls and F1 Angus-Holstein cows. All calves were weaned at an average age of 300 days and received an gg_libitum grain ration on pasture until mid-November when all calves were confined and fed 2.7 kg hay daily plus gg_libitum grain. Mean values over years for steer and heifer 205 day adjusted weaning weights (kg), weight/day (kg), slaughter weight (kg), and slaughter age were 248.8, 222.9; 0.97, 0.89; 435.1, 409.8; and 447.1, 448.1, respectively. Sire x sex interactions were not important for carcass traits and were significant for 205-day weight only. 46 Klosterman and Parker (1976) examined the effect of sex on the net energy value of corn silage and ground ear corn when fed separately or in combination to choice quality Hereford steer and heifer calves. Steers were slaughtered at approximately 454 kg and heifers at 386 kg. The experiment was conducted in each of 2 years with 14 heifers and 14 steers assigned to the corn silage, corn silage plus corn grain, and corn grain rations. Heifers were consistently fatter than steers and consumed more dry matter per unit weight on all treatments. There was, however, very little difference in amount of dry matter required per unit gain. Averaged over 2 years, net energy values of the rations (maintenance plus gain, Mcal/lOO lb DM) for steers and heifers were: corn silage, 62.7, 73.3: corn silage plus corn grain, 69.0, 72.0; and corn grain, 71.8, 70.6. Thus, the net energy value of the corn silage ration averaged 16% higher when fed to heifers than when fed to steers. Since this difference was not observed with the other rations, it was concluded that heifers were especially adapted to a high silage program. The advantage of greater efficiency of energy conversion in heifers was questioned, however, since it appeared they had to be fed to a higher body fat content to reach the same quality grade as steers. Bradley gt_gl, (1966) analyzed the records of 34 Hereford and 33 Hereford-Red Poll steer and heifer calves born in two years. Calves were the progeny of two Hereford bulls, one selected for high rate of gain and efficient feed conversion (1.33 kg daily and 5.63 feed/gain) and the other for poor rate of gain and feed conversion (1.01 kg daily 47 and 8.28 feed/gain). One-half of the Hereford and Red Poll cows were bred to each bull. All calves were individually fed a 70% TDN, 9% digestible protein ration for 208 days (both years). Main effects of sex, sire, and breed of dam were considered since sex x sire, sex x breed of dam, and sire x breed of dam interactions were not significant. Weaning weights were adjusted to a 275 day basis. An asterisk denotes significant difference for the main effect in question. §§x_ Sire Breed of dam High Lgy Trait Steers Heifers ga'n gain Hereford Red Poll Preweaning ADG, kg 0.86* 0.80 0.85* 0.81 0.75 0.91* Weaning wt, kg 269* 252 267* 254 237 284* Postweaning ADG, kg 1.01* 0.86 0.99* 0.88 0.95 0.92 Final wt, kg 479* 431 473* 436 434 475* A sire x sex interaction was noted in feed conversion with heifer calves sired by the high-gaining sire significantly superior to those sired by the low-gaining sire while no difference was observed in steer progeny. Rib eye area as a ratio to carcass weight was not different between steers and heifers. Bruin §t_gl, (1977) compared the performance of yearling Hereford heifers (319 kg initially) receiving Synovex-H (S), MGA (M), and Rumensin (R) in various combinations. All heifers were fed rations composed of 4.38 lb of corn silage dry matter, 0.91 lb supplement dry matter, and a full-feed of high moisture corn. Daily gains were 48 improved by S (2.84 y§_3.03 lb) and M (2.85 y§_3.02) but not by R (2.98 y§_2.89). The combination of S and R improved daily gains while R without S lowered gains. Daily intakes were predictably lowered by R but not S or M. Feed/gain was improved by S (6.28 y; 5.89), M (6.24 y§_5.92), and R (6.16 y§_6.01). Returns per head (3) for the various treatment combinations were: control (no additives) 21.93; R 13.72; M 23.49; Mi-R 21.08; S 17.59; Si-R 21.97; Si-M 23.90; Si-Mi-R 27.12. Carcass characteristics were adjusted to similar hot carcass weight and were not appreciably influenced by treatment. Ayala (1974) compared individually fed Holstein and Angus bulls, steers, and heifers. Approximately one-half of the animals in each sex-breed group were fed gg_libitum and one-half were fed at 70% §g_libitum. A pelleted ration of ground corn, soybean meal, alfalfa meal, and oat hulls was fed. One or two bull(s), steer(s), and heifer(s) per breed-intake level was slaughtered at 63, 140, and 224 days on trial. Four bulls and heifers per breed were killed initially. Results were summarized for three feeding periods: 0 to 63 days, 63 to 140 days, and 140 to 224 days. In 8 of 12 cases, steers gained more weight (2.3 to 25.6%) and were more efficient (2.6 to 23.2%) than heifers. The trends were more consistent at the §g_libitum level of intake and during 0 to 63 days of growth. Simpfendorfer (1974) compared Angus and Holstein bulls, steers, and heifers in body composition studies. Rates of increase in water, protein, and ash relative to increases in empty body weight were significantly higher in bulls than in heifers within both breeds. 49 Rates of fat accretion were higher in heifers y§ bulls. Holstein heifers gained water, protein, and ash more rapidly, but gained fat and energy less rapidly per unit change in empty body weight than did Angus heifers. Preston gt_gl, (1963) compared the feedlot performance and carcass merit of 17 Friesian steers (FS), 25 crossbred Angus steers (AS), and 33 crossbred Angus heifers (AH). Dams of crossbred calves were either Ayrshires or Friesians. All calves were placed on exper- iment at 84 days of age and were fed a complete ground diet (one-third roughage) §g_libitum. Heifers were slaughtered at 350 kg and steers at 400 kg. Initial weights were similar and days required to reach slaughter weight were 344, 356, and 354 for FS, AS, and AH groups, respectively. Feed conversion efficiency values (as 100 x gain/starch equivalent intake) were 25.6, 24.5, and 23.4 and fat content of the 10th rib (%) was 22.5, 31.2, and 36.5% for FS, AS, and AH groups, respec- tively. Overall "carcass quality scores" were computed for the three groups based on several chemical analyses and subjective scores of conformation, marbling, color, and firmness. Overall scores were 58, 67, and 68, respectively. Cooper g§_§l, (1972) compared 161 Hereford steers and 162 heifers in a 2-year study. Data were adjusted (within sex and year) by regression techniques to a carcass grade of low choice. Rations (dry matter basis) for all cattle were approximately 35% alfalfa haylage, 14% corn silage, and the remainder barley and supplement. Final weights, average daily gains, days of feeding to reach equal 50 grade, feed/gain, and feed cost/100 lb gain for steers and heifers were 1,038, 909 lb; 2.39, 2.02 lb; 211, 200 days; 7.45, 8.29, and $13.30, 15.14, respectively. All differences were significant at P<:.01. When adjusted to equal grade, heifers were fatter than steers (1.60 yg 1.78 cm), an observation also noted by Klosterman and Parker (1976). Final carcass weight, rib eye area, yield grade, and dressing percentage for steers and heifers were 290, 256 kg; 73.5, 64.5 sq cm; 3.48, 3.79; and 61.52, 63.03%, respectively. Based on these results, extensive economic data were presented to predict the price which could be paid for feeder heifers relative to steers given various market prices. If one lot of cattle were fed per year and the lot contained equal numbers of either steers or heifers, feeder price differentials were $3.00 to $9.00 depending on the various price relationships considered. Klosterman g£_gl, (1968a) compared 212 Hereford, Charolais, and Hereford x Charolais steer and heifer calves under two systems of management (3 years). A portion of the calves of each breed were creep fed, fattened in dry lot, and slaughtered at 12 to 14 months of age (creep system). The remaining calves were not creep fed, wintered, grazed, fattened in dry lot, and slaughtered at 18 to 20 months of age (deferred system). Feedlot gains (lb) for steers and heifers on the creep and deferred systems were 2.24, 1.93 and 2.57, 2.41, respec— tively. Age of slaughter (days) was 435, 433 and 605, 607 for steers and heifers on the two systems. Carcass grades were similar between 51 sexes and averaged high good for creep and average good for the deferred system cattle. Sex x management system interactions were noted for rib eye area, fat trim, % edible portion, edible portion produced daily, and carcass length. In all cases differences between heifers and steers became smaller with increased age at slaughter (deferred system). There was a smaller decrease in edible portion produced daily with increasing age for heifers y§_steers. Thus, heifers appeared to be more suitable than steers for deferred systems of management. Feedlot data from previous years, where breeds and systems of management were the same but complete cutout data were not available, were pooled with the above results to give 6 years performance data (n==281). All cattle were fed ground ear corn, soybean meal, and hay. Results by management system and breed were as follows: Hereford Charolais Crossbred Steers Heifers Steers Heifers Steers Heifers Creep system: Final wt, lb 838 797 1,037 955 1,022 891 Daily gain, 1b 2.05 1.82 2.27 2.04 2.28 2.05 Daily intake, lb 15.9 15.8 19.0 18.0 19.1 16.9 TDN/gain 5.32 6.18 5.61 6.32 5.47 5.92 Deferred system: Final wt, lb 978 949 1,175 1,073 1,114 1,037 Daily gain, 1b 2.54 2.30 2.67 2.44 2.60 2.30 Daily intake, lb 21.7 21.1 23.6 23.5 23.7 22.5 TDN/gain 6.31 6.39 6.55 6.93 6.62 6.93 52 Hedrick g§_gl, (1969) compared the feedlot performance and carcass characteristics of half-sib Hereford bulls, steers, and heifers. In one trial, cattle were fed a ground mixed ration (75% ear corn) gg_ libitum. One-half of each sex group was slaughtered when individual animals attained a live weight of approximately 400 kg (early kill) and the other half at 500 kg (late kill). Steers were 10 days younger in age at slaughter and were fed for approximately 20 days less in the feedlot. Combining kill groups, there were no differences in total gain, slaughter weight, or TDN/kg gain. The latter values were 6.08 and 6.30 for steers and heifers, respectively. Combined over kill groups, analysis of the carcass character- istics data indicated significantly higher values for heifers y§_steers in marbling score, fat thickness, percent fat trim, and ether extract in the longissimus muscle. Higher values for steers were found for percent retail yield and percent bone. Lasley §t_gl, (1971) compared the carcass quality character— isticsl of heifer calves of the Angus, Charolais, and Hereford breeds and their reciprocal single crosses to determine the amount of heter- osis in the various traits. Data included 112 short-fed (approximately 190 days) and 106 long fed (approximately 260 days) heifers produced in the 3 years 1965, 1966, and 1967. The first calf crop was full-fed a 91% ground ear corn ration (remainder soybean meal) while calf crops 2 and 3 were fed 75% cracked corn, 15% grass hay, and 10% supplement. Heterosis effects were negligible among the various measures of carcass quality examined (carcass conformation, marbling, WB shear, quality 53 grade). Bull breed by cow breed interactions were significant for carcass conformation grade for short-fed heifers. The Angus x Charolais combination was superior to all other combinations in measures of carcass quality. The level of mean differences among reciprocal crosses indicated that the Charolais breed was preferable to Angus when used as the male parent. The authors thus concluded that for improvement in carcass traits it would be desirable to use Charolais sires on Angus dams and full-feed the crossbred heifer for about 6 months. Jain gt_gl, (1971) also reported the growth traits of heifers in the experiment previously described (Lasley gt_gl,, 1971). Breed of bull, breed of cow, and year effects existed for most of the traits considered (initial wt on full feed, feedlot average daily gain, slaughter wt, daily live wt gain, daily carcass wt gain). Interactions of breed of bull with breed of cow were highly significant for short- fed heifers. There were no significant heterosis effects in the case of long-fed heifers. Short-fed crossbred heifers were superior to straightbreds by 7 to 8% for nearly all traits. It was concluded that full utilization of heterosis would occur by placing heifers on full feed for a period of about 6 months. Comparisons of various crosses indicated the most improvement in growth would be realized with Charolais sires and Hereford dams. It is well known that, when of comparable quality, heifers fatten at lighter weights than steers although the influence of sex on muscle to bone ratios at various stages of growth is uncertain 54 (Berg and Butterfield, 1968). Cahill (1964), however, quoted several studies showing a higher boneless beef to bone ratio in heifers than in steers. He thus concluded that careful marketing management of heifers might increase the relative value of their carcasses. Suess gt_gl, (1966) obtained palatability and quantitative carcass data on 88 Angus steer and heifer progeny from four herds representing eight sire groups. Calves were obtained at weaning and fed gg libitum a ration approaching 3:1 grain to roughage ratio. Animals were placed on test simultaneously in each of 2 years and an equal number of steers and heifers slaughtered at 386, 424, and 455 kg. There were no significant differences in percentage retail yield between steers and heifers. Significant interactions involving sex, weight group, or sire indicated that maximizing retail yield involved considerations other than the main effect of these factors. Palatability (taste panel) was not influenced by sex or weight group but interactions involving sex, weight group, or sire were significant for carcass grade. Extended feeding to increase live weight from 386 to 455 kg increased weight of retail yield with no significant change in carcass grade, marbling, or palatability. Breidenstein gt_gl, (1963) compared the carcass characteristics of 78 steer and 93 heifer carcasses "selected in a packing plant to be similar in characteristics presumed to be associated with retail yield.” External fat was removed to an average thickness of 0.3 in and internal fat was removed as completely as possible. Bone was also removed from nearly all cuts. Means observed for steers and heifers were as follows: 55 Side wt (1b) 278.7, 281.2; fat thickness at 12th rib (cm) 1.34, 1.45; kidney and pelvic fat (lb) 7.87, 9.28; rib eye area (sq in) 10.94, 11.34; quality grade (l9= low choice) 19.1, 19.7; total retail product (% of side wt) 62.86, 59.95. Significant differences were noted for side wt, kidney and pelvic fat, rib-eye area, quality grade and retail yield. Garrett and Hinman (1971) analyzed the fat content of trimmed beef muscles taken from four retail cUts. There were 36 choice and 36 good carcasses examined. 0f the choice carcasses, two steers and two heifers were included in each of the yield grades 2, 3, and 4 for each of the marbling scores small, modest, and moderate. The design was identical for carcasses grading good except marbling scores were trace, slight, and small. The amount of fat of all samples was related to quality grade, marbling score, and sex and to a lesser extent to yield grade. Compa- rable cuts from heifer carcasses generally averaged 0.5 to 1% higher in ether extract when compared to steer carcasses of the same quality and yield grade. Heifer carcasses were fatter based on gross carcass composition and contained more kidney fat than steers. Ihjluence of Cattle Type and Ration Energy Level on Feedlot Performance gflgyCarcass Characteristics A consistent observation of essentially all comparative feeding trials is an increased rate of gain as energy density of the diet increases, assuming adequate protein supplementation (for example, 56 Jesse §t_gl,, 1976b; Prior gt_gl,, 1977). When fed various rations cattle are thought to regulate feed intake in order to maintain constant energy intake at some ”set point” (Montgomery and Baumgardt, 1965). Thus, the energy density of a ration will reach a point above which energy intake is not increased. In practical terms, the levels of corn in corn-corn silage rations above which performance does not improve have been reported as 70 to 80% (Jesse, 1976a; 1976b; Fox, 1977). Thus, emphasis in this section will be placed on the effects of energy level and cattle type on the composition and efficiency of gain rather than studies reporting only gain data for cattle of a single type fed various levels of energy. Though commonly overlooked, the importance of comparing cattle at proper endpoints is not a new concept. The impact of body size and body composition differences on efficiency of feed utilization in time or weight constant trials was recognized and discussed by Stonaker 9; pl. (1952), Knapp and Baker (1944), and Guilbert and Gregory (1944, 1952). Even earlier, Kleiber (1936) stated that total efficiency of energy utilization was essentially independent of body size. Smith (1975) provided data relating cattle type to feed efficiency when trials were evaluated on the basis of constant age, weight, or body composition (5% fat in longissimus muscle). A wide variety of cattle types were represented in the studies and the marked effect of trial endpoint on ranking of the breeds for feed efficiency (TDN/gain) was illustrated. 57 In the absence of reliable feed intake data, attempts have been made to find a proxy for feed efficiency based on some measure of growth. Average daily gain has been used but, as indicated above, is largely inappropriate for animals of varying size (Kleiber, 1936). Smith (1975) proposed the use of “relative growth rate," defined as average daily gain divided by the mean body weight during the feeding period. However, it was clear from the data presented that the rela— tionship between relative growth rate and TDN/gain was not high when various types of cattle were compared at 5% longissimus fat (r= 0.44). However, within a breed or type the relationship would likely be higher. Klosterman and Parker (1976) found that "rate of maturity” (wt per day of age/slaughter wt at low choice, or more simply, l/age at slaughter) was related to TDN required during the postweaning period (r= —0.63). Hedrick (1972) pointed out an early study (Watson, 1943) where "optimality" was based on various measures of product produced. Optimal slaughter weight of full-fed steers on the basis of edible protein per unit protein intake was at 336 kg live weight (22% carcass fat). When evaluated energetically, a 680 kg weight was most efficient (carcass fat 35%). When both protein and fat were considered in relation to consumer preference, a 460 kg animal was superior (carcass fat 24%). Not all studies reviewed in this section compared cattle types at comparable endpoints. However, the conditions under which various trials were conducted will be pointed out where possible. Although reference is made to the older literature, more recent studies will be stressed since they more adequately represent the cattle types presently fed in practice. 58 While ”compact“ and ”comprest" cattle were preferred during the 1950's and early 60's, research during that time clearly indicated the superior gain ability of larger framed cattle (Stanley and McCall, 1945; Stonaker g;_ 1., 1952; Knox and Koger, 1946). It was also shown, however, that the increased rate of gain did not imply increased effi- ciency of feed conversion (Stonaker gt_gl,, 1952). Many of the more recent studies reviewed subsequently have supported these early observations. Kauffman (1977) studied the relationship of muscle shape to feed efficiency in a comparative slaughter trial. Forty-eight steers were classified subjectively for degree of muscling (angular to bulging). Test animals were of Angus, Brown Swiss, Charolais, Holstein, and Longhorn breeding, with four "double-muscled" cattle included. At constant empty body weight or constant fat, muscling (shape) did not significantly effect the conversion of feed to fat-free muscle. However, muscular animals were leaner and more efficient at a given chronological age. Brown gt_gl, (1973, 1974) evaluated the relationships among Preweaning measures of size and shape and postweaning performance of Hereford and Angus bulls. They concluded that final weight, total gain, and feed consumption were more predictable from shape and overall size than feed conversion. The simulation model of Fox and Black (1977) is in general agreement with these conclusions as differential intakes and rates of gain are predicted for cattle of varying frame size while feed conversion is constant. 59 Thomas and Cartwright (1971) compared Angus-Jersey (AJ), Charolais (C), and Hereford (H) calves in the feedlot. Feed conversion values were 8.1 (H), 8.6 (C), and 8.8 (AJ) although the results were difficult to evaluate since the trial was conducted on a time-constant basis. Cow-calf data (kg total feed/kg calf weaning wt) favored AJ over H over C. Ellersieck §t_gl, (1977) utilized records of 450 steers (6 years) of the Angus, Charolais, and Hereford breeds (and all reciprocal crosses) to determine the effects of heterosis on feed/gain. Two management systems were used in feeding out the steers. Steers in system 1 were pastured after weaning for 170 days and then placed in the feedlot (75% shelled corn) for 140 days. System 2 steers were placed in the feedlot immediately after weaning for 196 days (same ration as system 1). Data were adjusted to a weight-constant basis. Interactions were not significant between the breed of sire and breed of dam in both management systems indicating little importance of heterosis. This was confirmed by specific and pooled comparisons of crossbreds and straightbreds. Smith _Euil- (1976a) presented postweaning performance data for 1,105 steers out of Hereford and Angus cows and sired by Hereford, Polled Hereford, Angus, Jersey, South Devon, Limousin, Charolais and Simmental bulls. Differences were large in postweaning average daily gain (range==l9%) and relative growth rate (percentage change in body weight daily, range==10%). Charolais and Simmental 6O crosses were fastest gaining while Jersey crosses were slowest. Breed group differences were large for feed conversion on a weight constant basis (range==23%), but were reduced when compared on an age constant (range==9%), or fat constant (5% longissimus fat, range= 12%) basis. Efficiencies to constant fat ranged from 20.65 Mcal ME/kg gain for Hereford x Angus crosses to 22.10 for Simmental crosses. Weights at slaughter (constant fat basis) ranged from 417 kg for Jersey crosses to 525 for Simmental crosses. Koch gt_gl, (1976) presented the carcass characteristics of these cattle evaluated by the three slaughter end- points indicated for the performance traits. At 5% longissimus fat, fat thickness was 9.9 mm in Jersey cross steers and 13.9 mm in straight- bred British steers. Yield grades were most desirable for Charolais cross steers. Differences in relative proportions of retail product, fat trim and bone were small when cattle were compared at similar fat. Koch and Dikeman (1977) studied the wholesale cut composition of cattle from the study described previously (Smith §t_gl,, 1976a; Koch gt_gl,, 1976). While some significant differences were found, breed group differences in percentage of retail product and bone in each cut were strikingly small. Similar observations were made by Mukhoty and Berg (1973) and Charles and Johnson (1976b). The influence of breed of sire upon growth and carcass Characteristics of 32 crossbred steers was examined by McAllister §§_gl, (1976). Polled Hereford (PH), Charolais (C), Limousin (L), and Simmental (S) sires were bred to random groups of Angus-Holstein F1 cows. PH-sired steers were slaughtered at 476 kg with the heaviest 61 steers of the other breeds slaughtered the same day. On this basis slaughter ages were 427, 420, 416, and 413 days for PH, C, L, and S steers, respectively. There were no significant differences in cut- ability or quality grade although the latter favored PH steers. PH steers averaged less for slaughter weight per day of age (1.07, 1.16, 1.17, and 1.17 kg for PH, C, L, and S steers, respectively), rib-eye area and percentage trimmed loin but were fatter than the other steers. Edible portion produced daily was higher for C and L steers. Results of a similar study comparing steers sired by British and French breeds were in general agreement with these observations (Adams §t_gl,, 1977). Ferrell g§_gl, (1978) presented results of three experiments in which the influence of dietary energy, protein, and cattle type on performance and carcass traits was examined. Breed groups included Angus, Hereford, Shorthorn, crosses of these breeds, and Charolais, Dairy, Limousin, and Red Poll crosses. Overall conclusions were complicated by variations in cattle type, slaughter endpoints, and environmental conditions among the three trials. While dry matter or metabolizable energy intake per unit metabolic weight did not differ by breeding group, weight gains so expressed slightly favored the small type steers. The authors suggested an effect of energy density of the diet upon carcass composition in that carcasses from steers fed the higher energy rations were heavier and fatter but had similar amounts of protein than carcasses from steers which received the lower energy diet. The "energy density effect" on POdy Composition is perhaps true in the broad sense but such evaluations 62 should be made on equal amounts of carcass gain and over similar body weight ranges. Feed/gain values slightly favored the small type steers. Energy or protein level interactions with breed type were not significant, a result also noted in other studies (Klosterman §t_gl,, 1968a; Freeman, 1969; Harwin §t_gl,, 1966). Lipsey §t_gl, (1978) compared carcass composition of 16 Main- Anjou cross (MA), 14 Gelbvieh cross (G), and 16 Hereford x Angus cross (HA) steers. All steers were fed the same ration in individual pens and slaughtered when they reached an energy coefficient endpoint of 8.0 Mcal of NE per kg gain. The unconventional method of standardizing final physiological maturity was based on the assumptions that: (a) adipose tissue weight gain is more expensive than structural tissue weight gain; (b) a strong relationship exists between partial efficiency and physio- logical maturity as expressed by carcass composition; and (c) the energy value of a feed used for weight gain above maintenance is constant. It was thus assumed that the use of net energy for production (NEp) for weight gain should be highly related to physiological maturity as expressed by carcass composition. Fed to a common NEp efficiency of 8.0 Mcal/kg gain, MA, G, and HA steers had the following values, respectively: average daily gain, 1.09, 1.12, 0.90; feed/gain, 10.5, 9.1, 9.0; final weight (kg), 600, 601, 506; fat thickness, 1.27, 1.37, 1.80; quality grade (12==10w choice), 12.2, 11.6, 11.7. There were no sigrfiificant differences in quality grade while HA steers differed from "Vi and G steers in all other traits. 63 The greater growth potential of the larger dairy breeds (primarily Holstein) y§_the smaller framed British beef breeds has been reported (Kidwell and McCormick, 1956). Garcia-de-Siles (1977) fed Hereford and Holstein steers to slaughter weights of 409 and 500 kg. Weight per day of age at 280 days, 365 days, and at slaughter was 16%, 18%, and 22% greater for Holsteins than for Herefords. Holsteins reached slaughter weight at an average 83 days younger than Herefords and feed efficiency from 270 days to slaughter favored Holsteins by 13%. Minish gt_§l, (1966) and Hanke §t_gl, (1964) reported faster but less efficient gains when straightbred dairy calves were compared to British breeds fed to an equal time and weight endpoint. When compared at a similar degree of finish, Wyatt g;_§1, (1977b) found increases in daily feed intake, total feed intake, and feed/gain as percent Holstein breeding increased from 0 to 25 to 50%. Dean gt_gl, (1976) found that progeny of Hereford and Hereford x Holstein cows gained faster (0.13 and 0.08 kg daily) than progeny of Holstein cows. Calves were sired by Angus and Charolais bulls and thus contained 0, 25, or 50% Holstein breeding. Calves of 25 and 50% Holstein breeding consumed more daily feed (4 and 11%), more total feed (14 and 43%), and required more feed/gain (9 and 27%) than beef breed calves. Bond gt_gl, (1972) compared Holstein, Jersey, Milking Shorthorn, Angus, and Hereford steers from 180 days of age to slaughter (55 to 60% of mature bull weight or 27 months of age if expected weight was not reached). Three rations were compared: 75% concentrate (C); 50% timothy-50% alfalfa hay (H); and the hay mix for five-sixths of the 64 finishing trial followed by ration C (HC). Two trials were conducted; pooled average daily gains were 0.80, 0.70, 0.58, and 0.50 kg/day for Holstein, Milking Shorthorns, beef breed, and Jersey steers, respectively. Although no breed x diet interactions were noted in the second trial, in trial 1 Holsteins and Milking Shorthorns gained at faster rates on diets C and HC than the remaining steers. Addi- tionally, Holstein steers gained at a faster rate on the H diet than the other breeds. Breed x diet interactions for carcass fat were noted in both trials. Mean carcass fat was 31.1, 38.5, 26.0, and 20.5% for beef breed, Milking Shorthorn, Jersey, and Holstein steers, respectively. Steers fed diets C and HC were more efficient in producing carcass calories. The general relationship of cattle type to carcass composition was discussed by Allen gt_gl, (1976). They reported that at similar body weight, each breed (presumably animals of similar frame size within the breed) or breed cross has a given ratio of body fat to body weight. The work of Cramer gt_gl, (1973) was cited, indicating that about 25% of the total body fat in "chemically mature" cattle is intramuscular, regardless of breed. Therefore, animals within a breed and frame size were assumed to have a particular degree of marbling for a specified weight. They further argued that with body weight and total body fat fixed as constants within populations, carcass cutability could only be improved by changing body fat distribution. Thus, genetic selection or some other means of altering fat distribution should be utilized to decrease the percentage of total body fat deposited in waste fat depots. 65 Regardless of breed or type, fat is normally deposited in preferential sites during the progressing phases of growth: viscera and kidney, intermuscular, subcutaneous, intramuscular (Andrews, 1958). Palsson and Verges (1952), working with lambs, reported that the deposition of intramuscular fat was more age than plane of nutrition dependent. Similar results were reported for cattle (Lawrie and Kirton, 1956). In a reported cattle type difference, Lawrie (1961) found beef breeds deposited intramuscular fat rapidly at 10 to 12 months of age while dairy cattle gradually marbled without a period of rapid depo- sition. These results were supported by the work of Berg and Butterfield (1968). Carcass comparisons of cattle of beef y§ Holstein breeding have been variable although in many cases the variability can be explained by differences in trial design. Holstein calves were found to be lower in quality and conformation grade than British breed calves when fed to equal slaughter weights (Garrett, 1971; Cole g§_gl,, 1964). However, Wyatt g;_gl, (1977b) found marbling scores and carcass grades of Holstein progeny were as high or higher than those for Hereford progeny when cattle were fed to a similar degree of finish. Dikeman §t_gl, (1977) compared the carcass characteristics of light (LB) and heavy British breed (HB), and heavy Holstein (HH) breed steers. Carcass weight (kg) and fat thickness (mm) were 241, 9.7; 328, 11.2, and 325, 8.1 for L8, HB, and HH steers, respectively. HB steers had significantly more external and total fat trim than 66 Holsteins but less bone and no differences in total retail cuts. The LB steers had a higher percentage retail cuts, less bone, and less external fat trim from the four major wholesale cuts than HH steers. HH steers had a higher proportion of their total fat in the kidney and pelvic areas, a result also reported by Charles and Johnson (1976a). Smith gt_gl, (1977) compared various biological types of cattle on a wide range of feeding regimes. Cattle classified as small type (169 head) were at least five-eights British, Jersey, or Red P011 breeding. Cattle grouped as large types (218 head) were at least one-half Brown Swiss, Charolais, Chianina, Gelbvieh, Limousin, Main Anjou and/or Holstein or other large domestic dairy breeds. Five feeding regimes were examined: A= winter growing ration, summer grazing, 60% forage finishing ration; B= same as A only 20% forage finishing ration; C= 97% forage finishing ration; 0= 97% forage ration switched to a 60% forage ration; E= 60% forage ration. There were two or three slaughter groups per feeding regime from which regressions were developed to adjust data to weight- and Composition-constant endpoints. Live weight gains were consistent with expectations based on the energy density of the rations although feed efficiency (Mcal ME/kg gain) did not differ by feeding regime or Cattle type. Composition of gain was markedly changed by feeding regime. Adjusted to similar carcass weight, a consistent pattern of regime effects were found for all measures of fatness (A= B< C= D< E). A feel'Procal ranking was noted for retail product weight (A= B> C= D> E). 67 Type x regime interactions were nonsignificant for both composition and palatability traits. Adjusted to 4% longissimus muscle fat, small and large type steers were similar in measures of fatness. A consistent trend existed for steers on regime C and D to be leaner than those on regime E while steers fed according to regimes A and B were fattest. The authors thus suggested that placing young cattle directly into the feedlot on moder- ate energy rations might be the best way to produce carcasses of desired quality grade with minimum fat. Prior gt_gl. (1977), in a comprehensive factorial experiment, studied the impact of dietary energy and protein on performance and carcass characteristics of different biological types of cattle. Two types of cattle (Angus-Hereford, small type; three-quarter or seven- eighths Charolais and Chianina Hereford or Chianina Angus, large type) were fed three energy levels (LE, 2.90; IE, 3.06; HE, 3.17 Mcal metab- olizable energy/kg) at three protein levels (LP, 10%, MP, 11.5%; HP, 13%). Corn silage-corn based rations were fed to all cattle. Two of the small type cattle from each replicate (all pens replicated except LP group) were slaughtered after 196 days on experiment and the other small types after 232 days. Two of the large type cattle from each replicate were slaughtered at 232 days on experiment and the other large types at 313 days when they were expected to be of similar composition to small types slaughtered after 196 days. There were no protein x energy interactions observed with either cattle type. Overall, dry matter intake was not influenced 68 by the energy density of the ration. During the first 232 days on trial, intake favored the large cattle types (8.6 y§_8.l kg/hd/day). Energy intake was limited by bulk fill in the small but not large type cattle. Total Mcal of metabolizable energy required to produce a kg of live weight gain was not influenced by ration energy level or type of cattle. Mcal of metabolizable energy required per kg retail product gained favored the LE groups in both cattle types. Although not pointed out by the authors, this probably indicates that sufficient energy was consumed by the LE groups of both cattle types for maximum protein synthesis. This is further supported by the fact that across the three energy levels (within a type and slaughter group) all cattle had similar amounts of total protein (kg) in their carcasses. Predictably, live weight gain responses due to protein level occurred largely in the 0 to 63 day time period. The authors concluded that for maximum efficiency and rate of gain at lighter weights, small type cattle should receive 0.77 kg of crude protein per head daily up to 325 kg body weight. Similarly, large type cattle should be fed 0.93 kg of crude protein daily to 348 kg body weight. Carcass composition at constant carcass weight, was altered by nutritional regime in small but not large type cattle. Adjusted to constant carcass weight, increasing dietary energy intake increased marbling score, quality grade, fat thickness, kidney and pelvic fat, and Yield grade. Increasing protein percentage in the ration had no significant affect on carcass quality or composition. 69 Jesse gt_gl, (1976a) studied the effect of ration energy level and slaughter weight on composition of gain in 56 Hereford steers. Corn-corn silage rations were fed in the following proportions: 30:70; 50:50; 70:30; and 80:20. Four steers from each ration were slaughtered at 341, 454, and 545 kg. The composition of empty body and carcass gain for a given weight was not affected by ration. Fat gain as a percentage of carcass gain increased from 27.5 to 48.6% as slaughter weight increased from 341 to 545 kg. However, fat as a percentage of carcass gain from 454 to 545 kg was 68.3% indicating a period of predominantly fat deposition. It becomes obvious from the studies previously reviewed in this section that trials examining the impact of ration energy level on carcass traits have not yielded consistent results. This is also evident in the reviews of Reid g:_gl. (1968) and Marchello and Hale (1976). Those observing effects of energy level on carcass composition include Prior gt_gl, (1977), Fox (1977), Ferrell §t__j: (1978), and Smith g3 El, (1977). Those reporting little or no effect include Jesse g: al. (1976a), Guenther gt_gl, (1965), Reid gt_ 1. (1968), Epley §t_gj, (1971), and Allen _t_l_. (1976). At least a portion of the incon- sistency can likely be attributed to differences in trial design such as slaughter schedule, cattle types compared, portion of the growth curve examined, degree of difference in energy level of rations co"lpared, total energy intakes, etc. Additional factors possibly affecting results have been discussed by Fox (1977). OBJECTIVES To examine the adequacy of energy levels recommended by the National Research Council for cows of varying mature sizes and genetic backgrounds when maintained in unsheltered northern climatic conditions. To compare the efficiency of nitrogen and energy utilization of cattle of four genetic types when fed high corn silage or high corn grain rations. To examine the effects of sex, selection, and crossbreeding on preweaning and postweaning performance and efficiency of growth of calves from four genetic backgrounds. To examine the impact of ration energy level on composition of gain and carcass characteristics when cattle of four genetic types are fed to similar finish. To compare the economics of production of steers and heifers of four genetic types when fed high corn silage and high corn grain rations. 7O MATERIALS AND METHODS Cow—Calf Trials Source and Genetic Background of Experimental Animals Cow-calf trials were conducted from December 16, 1975 to September 9, 1976 (trial 1) and from November 23, 1976 to September 19, 1977 (trial 2). In each trial, ten pregnant cows, representative in age and weight, were obtained from each of the four genetic types maintained in a breeding project at the Lake City Experiment Station, Lake City, Michigan. Genetic groups compared were Unselected Herefords (USH), Selected Herefords (SH), Angus x Hereford x Charolais crossbred (AHC), and Angus x Hereford x Holstein crossbred (AHH). The Lake City breeding project began in 1966 with a herd of 200 grade Hereford cows from one source. The cows were initially allotted to four groups of 50 cows each. No selection was practiced in the USH group and the mating system was random. Each year the first four USH bull calves born by different sires were retained and used as clean-up bulls the following year. At the termination of the breeding season, semen was collected from each clean-up bull, frozen, and used to inseminate cows the next year. In the SH, AHC, and AHH groups, superior bulls from AI studs were used, selected primarily on their yearling weight. Replacement heifers in the three selected groups were retained on the basis of 71 72 their unadjusted yearling weight at a rate of 20% per year. USH replacement heifers were saved without regard to weight, but were representative of the age groups of SH, AHC, and AHH replacement heifers. A summary of the mating systems and selection practices used ir1 establishing each group are included in Table 3. Additional infor- 1na1:ion on the source, selection, management procedures, and past per- fornnance of these herds has been presented by Magee and Greathouse (1S969, 1970, 1971, 1972, 1973); Magee (1974); and Magee and McPeake (1975, 1976). Expyerimental Design and Rations The experimental design, initial weight and condition, and genetic background of cows is indicated in Table 3. Mean age of trial 1 cows was similar for all groups and each group included two first-calf heifers. AHC and AHH cows were three-breed crosses con— taining an average 30% Charolais or Holstein breeding, respectively. Initial weights for USH, SH, AHC, and AHH cows were 382.8, 433.6, 480.4, and 479.4 kg, respectively. Cows were in similar condition, averaging 0.36 cm external fat. Trial 1 cows received corn silage and a soybean meal—mineral SUPPlemerrt (10% ration crude protein) throughout the trial. The trial was c0nducted concurrently with feedlot trial 2 and feed ingredients Were 0f the same source (Table 8). 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After calving, cows received the level recommended for lactation based on their pre-calving body weight. Due to the marginal condition of the cows, feed offered was increased 25% above the lactation level on April 7, l976, corresponding to 52 days berfore breeding. All cows received this level for the remainder of the experiment. Trial 2 animals included ten pregnant cows per type; eight cows frxmn trial 1 and 32 additional cows from the Lake City herd (Table 3). Tr"ial 2 cows were initially heavier and fatter than trial l cows. Avearage age (years), external fat (cm), and weight (kg) by type were: 5, 0.75, 440.7; 4.8, 0.84, 505.2; 3.8, 0.69, 54l.6, and 4.7, 0.58, 533.9 for USH, SH, AHC, and AHH cows, respectively. AHC and AHH cows contained an average 36% Charolais or Holstein breeding, respectively. Each group of ten cows was divided into two groups of five cows each, based on body weight and age with one first-calf heifer included in each sub-group. The sub—groups within a type received either a low (NRC) or high (NRC+ 25%) energy ration based on the energy requirements recmmnended by the National Research Council (NRC, l976). The revised beef cattle requirements issued by the NRC in 1976 subdivicies pregnancy requirements into the mid and late trimester of pregnancjl, increasing previously recommended levels (NRC, l970) by aDproximately l0%. Additionally, lactation levels were presented for cows of superior (over 10 kg milk/day) v§_average milking ability. AHH cows were fed levels recommended for cows of superior milking ability; USH, 3H, and AHC cows were fed at the level for average milking ability. . , 75 As in trial l, trial 2 cows received corn silage and a soybean meal—mineral supplement (l0% ration crude protein) throughout the study. The trial was conducted concurrently with feedlot trial 3 and feed ingredients were of the same source (Table l0). As indicated previously, feed amounts were based on NRC (l976) recommendations and ccnnsisted of three phases. Cows received levels for dry pregnant cows, nriddle third of pregnancy, for 56 days. From 56 days to calving, levels rwacommended for the final third of pregnancy were fed, including allow- an<:es for growth of yearling heifers. At calving, lactation levels \NQY‘E initiated and continued for the remainder of the trial. MaJiagement Procedures The corn silage and supplement was mixed in a horizontal batch mixer and fed as a complete ration once daily. Cows were group fed within type (trial l) or within type and energy level (type 2). All cows \Nere individually weighed every 28 days and external fat over the l2th rib was estimated using a Scanoprobe.1 Initial and final Weights were obtained after a l6 hr withdrawal from feed and water Internuadiate period weights were on an off-water basis. Additionally, in trial 2, height of cows at the hooks was measured at the beginning and enci of the trial and weight/height ratios were calculated as a Comparative method of determining cow body condition. Trial l cows were maintained separately by type in four l8.5 x 52 m dry lots without shelter or windbreaks although small _________________________ lscanoprobe, model 73l, Ithaco, Inc., Ithaca, New York, 48850. 76 shelters were provided for calves. Similar facilities for trial 2 cows were used except eight 6.l x 46 m lots were utilized. Cows remained outside until calving was imminent at which time they were moved to a sheltered, open—fronted, calving area, again separated by type (trial 1) or by type and energy level (trial 2). When one-half of the cows in each group had calved they were returned to the dry lot and the remaining cows were placed in the sheltered calving area. Cows which lost their calves were removed from the experiment. Newborn calves were given recommended levels of vitamin A and a \Iitamin E-—selenium preparation. Iodine was applied to the navel Of' all calves and birth weights were obtained immediately. Bull calves werwa castrated at 2 to 3 weeks of age and calves were dehorned with cale;tic paste where necessary. Calving seasons extended from Janu- arj/ 22 to April 7, l976, for trial l, and from January 30 to April 2, l97”7, for trial 2. Weaning weights were obtained at the conclusion of teach trial and adjusted to a 205 day, mature dam, bull calf basis. Rebreeding performance was examined for trial l cows only. Two injections of Prostaglandin qu, ll days apart, were used to SYnchronize estrus. All cows were artificially inseminated 80 hr following the second injection, on May 28 and 29, l976. Blood samples were secured from all cows immediately before breeding and were anaU’zed for progesterone. Cows with serum progesterone levels of 1-0 ng/ml or greater were classified as cycling. All cows were observed for estrus for 30 days post-breeding and a second AI service performed if needed. 77 Climatological data were collected daily at a site 275 m northwest of the trial site. Data from monthly summaries (Michigan Climatological Data, l975-77) are presented in Table A.5 for trials l and 2. Metabolism Studies Experimental Animals Two USH, SH, AHC, and AHH steers were used in each metabolism study. Trial 1 and 2 metabolism steers were representative of steers {flaced on feed in feedlot trials 2 and 3, respectively. Mean initial weVights (kg) of trial l and 2 steers were 2l8, 269, 3l0, and 354 and 12!}, 184, l77, and 203 for USH, SH, AHC, and AHH steers, respectively. Tr"ial Design, Rations, and Collection Procedures Metabolism studies were conducted in the winter (trial l) and fal 1 (trial 2) of 1976 in an environmentally controlled metabolism roonL Steers were confined to individual 9l x 244 cm stalls designed to allow the collection of both feces and urine. Each trial consisted of two phases in which one steer per type initially received either a high silage or a high grain ration. Rations were then switched for the second phase so that all steers received both diets. r The high silage and high grain rations and their analyses for both trials are presented in Table 4. Trial l and 2 steers were fed rations consistent with the initial diets fed to steer mates in feedlot trials 2 and 3, respectively, and feed ingredients were from a common ..- Table 4. Rations Fed to Unselected Hereford, Selected Hereford, Angus x Hereford x Charolais, and 78 Angus x Hereford x Holstein Steers in Metabolism Studies Trialsl , 2)a Trial l Trial 2 High silnage High grain High silage High grain Int. ref. ratio ration, ration, ration Item no. % of 0M % of DM % of DM % of DM Corn, aerial pt, w ears, w husks, ensiled, mature, well-eared mx 50% mn 30% dry matter 3-08-153 88.00 20.00 86.00 20 00 Corn, dent. yellow, grain, gr 2 US 4-02-931 67.40 66.30 Soybean, seeds, meal solv-extd 5-04-604 11.04 10.31 13.05 11.00 Limestone, grnd 6-02-632 0.26 1.96 0.21 1.50 Phosphate, deflourinated, grnd 6-01-780 0.40 0.45 Potassium chloride. KCl 6-03-756 0.91 Trace mineral salt 0.26 0.29 0.25 0.25 Vitamin Ab 0.02 0.02 0.02 0.02 Vitamin 0° 0.02 0.02 0.02 0.02 Percent of ration dry matter: Crude uprotein 13.50 14.50 13.40 14.40 Calc 0.49 0.80 0.50 0.69 Phosphorouse 0.34 0.33 0.36 0.34 Net energy, Mcal/kg dry matter:2 Maintenance 1.59 2.03 1.60 2.02 ain 1.02 1.33 1.02 1.32 Two steers per type received each ration in each of two trials. b30,000 IU vitamin A per g. C3,000 IU vitamin 03 per g. dDetermined by laboratory analysis. eCalculated from average nutrient composition (NRC, 1976). 79 source. An 18-day adaptation period was used to adjust animals to the stalls and their respective diets. Steers assigned to the high grain ration were initially offered an 85% corn silage ration (dry matter basis). The silage portion of the diet was then decreased 5% daily with a concurrent increase in the corn and supplement portion. In this manner steers were gradually adapted to a full-feed of 80% corn and supplement by day 11. The readjustment phase, in which rations were switched, was 16 days in length with an 11 day adaptation to full grain feeding as previously described. The daily allotment for each steer was mixed in a small horizontal mixer and offered once daily. Steers were fed ad libitum and refused feed was removed daily, weighed, and recorded. Grab samples of all rations and weighbacks were secured daily, composited for each steer, and frozen. At the conclusion of each collection period, composite samples were partially thawed and thoroughly chopped in a Hobart food chopper. A 1500 g subsample was then retained for later analysis. Urine was collected into large plastic carboys in which 200 ml of 18 N sulfuric acid was added to prevent escape of ammonia or other nitrogenous products. Carboys were emptied at least every two days and the urine collected was diluted to a total volume of 10 liters with water. A 10% aliquot was secured, composited for a given steer, and stored at 5 C until the conclusion of the collection period. A 1 liter subsample was then obtained and frozen for later analyses. _. z ..._..L-a....., 1' I 80 - Total feces were collected in plastic-lined steel troughs behind each steer. Feces were removed at least every two days, weighed and a 10% subsample secured. Subsamples were composited for each steer and frozen until the end of the collection period. At that time the composite samples were thoroughly mixed and a 2 kg sample removed and frozen for later analyses. Laboratory Analyses Dry matter of rations and orts were determined by drying 100 g samples in a forced-air oven for 48 hr at 50 C. Similar procedures were used for fecal samples although a 200 9 sample was used and 25 ml of 4 N sulfuric acid was mixed with the sample prior to drying. Total nitrogen of all samples was determined with a Technicon Auto Kjeldahl System. Sample sizes were 4 g, 1 g, and 4 ml for wet rations and orts, dry feces, and urine, respectively. Total energy was determined in an adiabatic bomb calorimeter. Diet 2 9 samples of rations and orts were used with the alcohol priming rnethod outlined by Colovos et__l. (1957). One ml of 95% alcohol was added to samples immediately preceding bomb assembly. The alcohol solution used in these determinations had a caloric value of 5.27 Mcal/ml. Fecal energy was determined on dried, pelleted 1 9 samples. Urine samples were prepared for combustion by adding 5 ml of urine to preweighed (approximately 350 mg) cotton balls and freeze drying for 48 hr. Energy value of the cotton was determined on triplicate samples. 81 Calculations Nitrogen retention (g/day) was calculated by subtracting urinary and fecal nitrogen excretion from nitrogen intake. Retention was also expressed as a percentage of nitrogen absorbed (apparent biological value) and as a percentage of nitrogen intake. Daily energy retained was calculated as energy intake minus fecal, urinary, and gaseous energy losses. It was necessary to estimate the latter and a factor of 8% of energy intake was used as suggested by Blaxter (1962). Metabolizable energy values of the rations were calculated as Mcal of energy retained per kg dry matter intake. Feedlot and Body Composition Studies Experimental Animals Cattle fed in three trials were 176 steer and 57 heifer calves of four genetic types (USH, SH, AHC, and AHH) from the Lake City Breeding Project which was previously described. The steers rep- resented essentially all male calves produced in each group from the 1974 through 1976 calf crops, with the exception of those used in initial slaughter or metabolism trials. Feedlot performance data for the 1974 steer calves (trial 1) were previously presented by Crickenberger (1977). Heifers fed were from the 1975 and 1976 calf crops and were those remaining after 50% of all heifers produced were removed as herd replacements. 82 As indicated previously, USH calves were the result of random matings while SH, AHC, and AHH calves were from groups where selection was practiced based on yearling weight. USH replacement heifers were thus saved without regard to weight but were representative of the age groups of the selected replacement heifers. Trial Design and Rations The design of feedlot trial 1 has been previously described by Crickenberger (1977) and is presented in Table 5. With the exception of the SH group, 16 steer calves per type were stratified by weight and divided into eight groupings of two steers each. One steer per group was then randomly assigned to either corn silage plus supplement (HS) or 40% corn silage plus 60% corn grain and supplement (HG), on a dry matter basis. Due to insufficient numbers of SH calves, six were fed the high silage ration and seven were fed the high grain ration. The experimental design and rations fed in trials 2 and 3 art: presented in Tables 7 and 9, respectively. Similar allotting PPC)cedures to trial 1 were used in these studies, although two changes weroe made in trial design. Five to eight heifers per type received a 1’l‘igh silage ration and steers assigned to the high grain ration re<363ived 20% corn silage and 80% corn grain plus supplement. Thus Witii an estimated grain content of corn silage of 50%, HG steers in trléil 1 received 80% concentrate rations y§_90% for trial 2 and 3 Stefiars. High silage rations were similar across all trials with Tation dry matter averaging 91% corn silage and 9% supplement. .Aouo— .umzv mm3~m> mmmgw>m Eoce uwuap=u_auw .mwmxpmcm xcoumconmP x2 vocWELmuoau .3; :32 25.3 o FEE: uxmr.o .Am\:H ooo.omv < :w5mum> ”Rm.~ .urem pmcwcwe wumgu ”Np.m .wcoumwsmF mx_.mm .mee econxom "cowu_moQEou Lmuume xgou .wm—.o .Am\=_ coo.mv o :WEauw> m$7: .Am\:H oco.omv < :PEmuw> Mn~.~ .upmm chwcwe mung» ”gm.m .muocamoga .Loa—umu "RN.~ .ocoumwewp “mo.~m .Fowe cmmnxom "=o_u_moqeoo coupes axon .cwmumpo: x utowwcm: x mamc< “::< mmwapocmzu x ucowwgoz x mzmc< "uzq nugowmgo: uwuuwpwm "2m decommgw: uwuomemca “Imam -._ e~.P ap.— mm._ co.p oo.p oo._ _o.P ammo om.p mm._ em.p om._ Km._ mm.p mm.— mm.P mucmcmucwmz a x\quz . _m.o mm.o Fm.o em.o m~.o 5N.o o~.o Nm.o we m~.o mm.o om.o em.o om.o _e.o mv.o om.o muu N.P— m.mp “.mp m.vp m.a m.op w.—_ p.m_ u:_wuogn wuacu as Leanne cc mo unmugoa co m.e a.n ~.F_ w.¢— o<~m «cwEm—aazm e.e N.@ w.“ m.—P wasp acoEmpnaam ~.mm “.mm m.om m.me :Lo m.oe e.om o.~m m.pe wczummoe cow: $3 98 Ndm 5% 823. ES x .Lmuume Lu cowumg cm mucowuwg :H w ow m cm =x< +vme «me-mmm mom-w—m wpm oh w o_ +vm< ewe-mom mam-mFm w—m eh m mm ux< o mp N «N :m +mom mmm1w~m mFm-NNN mum oh m N_ +mom mam-w—m wpm-NNN mum 0» w Fm :m: mgwmpm mg .usmwm: .Ewcw .0: mx .a;m_m3 .Ewcw .0: max“ xwm .oz cm; .02 can mmFHuau cowumg :_~Lm saw: :owumc mmmpwm cow: 11111ii11iii111111111111111111111111 — Peace “crummu to» mcoauam ecu :uwmwo _uucme_cwaxm .m o_aah 84 Ration ingredients were analyzed monthly and their mean nutrient composition for trials 1, 2, and 3 are presented in Tables 6, 8, and 10, respectively. All rations were adequately supplemented with calcium, phosphorous, trace mineral salt, and vitamins A and 0 according to the guidelines of Fox (1975) and Fox and Ritchie (1975). Supple- mental potassium was added to the high grain ration fed in trial 3 due to some problems with stiffness noted in trial 2, which suggested a potassium deficiency. A declining protein level supplementation system was followed in all trials. Crude protein requirements and ration protein levels were based primarily on the animal's stage, composition, and rate of growth and protein quality of feedstuffs as discussed by Fox ____1. fl (1977). Specific protein requirements for cattle of various weights and frame sizes and fed various combinations of corn and corn silage have been presented by Fox and Black (1975). Management Procedures Each year calves were transported by truck 220 km from Lake Ci ty, Michigan to the Beef Cattle Research Center immediately after Weéining. Incoming calves were vaccinated for pasteurella, IBR, BVD, ancj P13 and were given recommended levels of vitamins A and D intra- mUSSCularly. A starting ration of 88% corn silage and 12% soybean meiil -mineral supplement was fed. The ration was balanced with calcium, ph<3813horous, trace mineral salt, and vitamins A and D as recommended by IWRC (1970). All calves remained on the starter ration for a .AommF .umzv cowpwmoneoo “sweeps: mmmcw>< .m tag me cesapw> DH ooo.mu .m can < swampe> 2H ooo.om0 a .mwmz—mcm keepmeoan An vmcwEmemom oo.om we swampw> oo.om o< :wEwpa> oo.oo_ u_mm _aLmCTE mange mo.o eo.m— No.mm oo.oc— own-_O1m uccm .ummeWLo:~emc .mpmgqmoca MW No.0 em.mm oo.oo_ mmo1NO1o teem .wcoumweve _N.N mN.o om.o om._m om.mw aoo-ao-m qum->_0m Fame .muwwm .cmwaxom mm.o No.0 om.o~ 00.0“ _mm1No-a m: N cm .cwmcm .ZOFsz .pcwu .cLou mm.o _N.o mm.o m_.m om.mm mmF1mo-m emppme zen Now :5 eom xe emcee-Fro: .wczpwe .vw__mcm .mxng 3 .mcmm 3 .pa _macoa .ccou x a no wcwwpoca mempume .o: “cwwumcmcH n n a wnzgo Ago .mw; .ch mepme ace mo “smegma F mege po—uwwa Low mwcwvvwemcH :owpmm mo soapwmoqeou pcwwcuzz .m wFamH 86 Table 7. Experimental Design and Rations for Feedlot Trial 2 High silage ration High grain ration Cattle Pen No. Pen No. Sex typea no. anim. Weight, kg no. anim. Weight, kg Heifers USH 1 8 To 218 218-254 254+ SH 2 8 AHC 3 8 To 263 263~299 299+ AHH 4 8 Steers USH 5 6 To 272 272-318 318+ 11 6 To 272 272-318 318—363 363+ SH 6 8 12 8 AHC 9 8 To 318 318-363 363+ 13 8 To 318 318-363 363-454 454+ AHH 10 8 14 8 Ingredients in ration dry matter, Corn silage 88.0 90.4 92.8 20.0 20.0 20.0 20.0 High moisture gorn 67.4 70.3 73 1 76.0 Supplement 174 12.0 9.6 7.2 Supplement 175C 12.6 9.7 6.9 0 Percent of dry matter Crude proteind 13.2 11.7 10.3 14.6 13.5 12.6 11.2 Cae 0.49 0.44 0.40 0.80 0.63 0.47 0.31 Pe 0.34 0.31 0.29 0.33 0.32 0.31 0.30 Net energyI Mcal/kge Maintenance 1.59 1.59 1.48 2.03 2.05 2.07 2.09 Gain 1.02 1.01 1.00 1.33 1.34 1 35 1.36 aUSH: Unselected Hereford; SH: Selected Hereford; AHC: Angus x Hereford x Charolais; AHH: Angus x Hereford x Holstein. Two steers (pens 10, 11) were discarded during the trial and data were completely removed. bDry matter composition: soybean meal, 92.0%; limestone, 2.2%; defluro. phosphate. 3.3%; trace mineral salt. 2.2%; vitamin A (30,000 IU/Q), 0.15%; vitamin 0 (3,000 lU/g), 0.15%. Dry matter composition. soybean meal 81. 8%; limestone, 15. 6%; trace mineral salt, 2 3%; vitamin A (30, 000 IU/g), 0.15%; vitamin D (3, 000 IU/g) 0.15%. Determined by laboratory analysis. eCalculated from average values (NRC, 1976). 87 .m Log me cesapw> 2H 89mU .m can < :wEapw> 2H ooo.omo .AommF .omzv cowpwmomeoo ucmwcpsc mmocw>3 uwcwEmewom oo.om no swampw> oo.om o< :wEwpw> oo.oo_ mem Fecmcwe momce mo.o wo.w_ No.mm oo.oo_ own-FO10 teem .wwpmcwcoz_$mu .mpmcamosm No.0 ew.mm oo.oo_ Nmo1No1o teem .wcopmwewe _N.N mk.o om.o mm.mm oo.om eac-<01m upxm1>Fom Fame .mcmwm .cmwnxom mm.o No.0 mm.o_ ow.mo _mm1N01e m: N gm .cwmcm .2o__m» .pcwv .ccou ma.o _N.o wN.o om.n om.Nm mmF-wo-m cmppae zen Nom :5 Nom xe cacao-Fsz .wgapme .vmpwmcm .mxmzz 3 .wcmm 3 .wa mecmm .ccou x a mo newwpoga mepme .o: ucmwnwcmcH n a n muzcu ago .emc .ch prpme Age No “smegma N _mvce “OFvwme Low mpcmwumcmeH cowpmm to covpemoaeou ucmwgpzz .w mFDmH 88 Table 9. Experimental Design and Rations for Feedlot Trial 3 High silage ration High grain ration Cattle Pen No. Pen N0. Sex type no. anim. Weight, kg no. anim. Weight, kg Heifers USH l 6 To 218 218-254 254+ SH 2 6 AHC 3 7 To 263 263-299 299+ AHH 4 7 Steers USH 5 6 To 272 272-318 318+ 11 6 To 272 272-318 318—363 363+ SH 6 8 12 8 AHC 9 8 To 318 318-363 363+ 13 8 To 318 318-363 363-454 454+ AHH 10 8 l4 8 Ingredients in ration dry matter, Corn silage 86.0 88.4 90.7 20.0 20.0 20.0 20.0 High moisture corn 66.3 69.2 72.2 75.1 Supplement 176 14.0 11.6 9.3 Supplement 276C 13.7 10.8 7.8 4.9 Percent of dry matter Crude proteind 13.3 12.3 11.2 14.3 13.5 12.5 11.5 Cae 0.50 0.46 0.42 0.69 0.56 0.44 0.31 Pe 0.36 0.34 0.31 0.34 0.33 0.33 0.32 Net energy, Mcal/kge Maintenance 1.60 1.59 1.59 2 02 2.04 2.06 2.08 Gain 1.02 1.02 1.01 1 3 1.33 1.35 1.36 aUSH: Unselected Hereford; SH: Selected Hereford; AHC: Angus x Hereford x Charolais; AHH: Angus x Hereford x Holstein. Two animals (pens l, 9) were discarded during the trial and data were completely removed. bDry matter composition: soybean meal, 93. 2%; limestone, 1.5%; deflour. phosphate 3 2%; tr‘ace mineral salt, 1.8%; vitamin A (30, 000 lU/g), 0.15%; vitamin D (3,000 IU/g), 0.15%.. cDry matter composition. soybean meal, 80.33%; limestone, 10.9%; potassium chloride, 6.6%; tl'ace mineral salt, 1. 8%; vitamin A (30, 000 IU/g), 0.20%; vitamin 0 (3,000 lU/g), 0.20%. dDetermined by laboratory analysis. 6Calculated from average values (NRC, 1976). .311":- .0 Log me :TEmuw> :H ooo.mU .m can < ceeape> DH ooo.omo .Amnmy .umzv covy_moaeoo pcwwcuzc omwcm>< n .mwm>_mcm ALQpMLODMF >2 nmcaesmumom oo.om to :wEmww> oo.oa o< ceaapw> oo.oo_ “Fem _mcmcwe ounce ¢¢.Nm oo.oo— mmm-moam Pox .mUwLo—cu Ezwmmmuoa mw mo.o wo.w— No.mm oo.oo— owm1—o-w vcgm .cwumcwgozpmmv .mpmcqmocm No.0 «w.mm oo.oo_ Nmm1NO1m ccem .wcoumme4 PN.N mn.o mm.o O¢.Nm oo.om wow-vo-m uuxw1>FOm Paws .mvwwm .cmmnzom mm.o No.0 oo.o_ om.Nm me-No-v m: N La .cwmgm .30—Fm» awcwu .ceoo mm.o _N.o wN.o mm.m om.mm mm—1wo-m prpwe act xom :E xom xe vwcmm1FFw3 .wczpme .vaewcm .mxmsg 3 .mcmw 3 .pa _mwcow .ccou ox an new mcwmwmwa mcwmmwe .embompcm pcwwuwgmcH mepme Ace wo pcwocwa m _mwch quumme Low mpcwwumcmcH cowpmm wo cowpwmoqeou ucmwcpzz .o~ mFamp - _‘_.___—.__.-— 90 minimum of 30 days, were closely observed for signs of sickness and treated if necessary. When calves were healthy and consuming expected amounts of dry matter, trials were initiated. A pour-on insecticide was applied to all calves to control grubs and lice. Trial 1 calves were implanted initially with DES and reimplanted with Ralgro subject to withdrawal requirements. Trial 2 and 3 calves received Synovex-H for heifers and Synovex-S for steers at recommended intervals throughout the trials. Cattle were fed ag_libitum and received their complete ration once daily. Ration ingredients were blended in a horizontal mixer just prior to feeding. Daily feed records were kept and refused feed was periodically removed, weighed, and recorded. Samples of all feeds vvere secured monthly and analyzed for dry matter (50 C for 48 hr) and nitrogen (Kjeldahl on wet samples). Rations were adjusted at the beginning of each 28 day period for changes in dry matter content of ingredients. All cattle were individually weighed at the beginning of the eexperiment and approximately every 28 days thereafter until removed ‘For~slaughter. Initial and final weights were obtained after a 16 hr wi'thdrawal from feed and water. Intermediate weights were on the biasis of a 16 hr withdrawal from water only. Two steers from trial 2 and one heifer and one steer from tr‘ial 3 were removed during the course of the trials. The loss of (Hie animal was treatment related with a high grain fed steer from trial 2 removed due to founder. The data from all four animals were 91 completely removed from the trials by estimating feed consumed from observed gains using the net energy requirement equations for steers and heifers as outlined by NRC (1976). All cattle were housed, 5 to 8 per pen, in concrete, bedded lots. Approximately one-half of the floor space of each pen was covered with a roof. Initial Slaughter Animals All initial slaughter calves were selected to be representative of those placed on feed in the feedlot studies. Ten steer calves (two to three per genetic type) were slaughtered at the beginning of trial 2. Dressing percentage and carcass composition data from these calves were used to estimate the initial carcass weight and composition of steers fed in trials 1 and 2. Similarly, l3 steer calves (three to four per genetic type) were slaughtered at the beginning of trial 3 to estimate the initial values of their steer mates placed on experiment. A limited number of heifers were available for initial Slaughter purposes. Three USH, two AHC, and three AHH heifers from trial 2 and two SH heifers from trial 3 were used to estimate the Tiiitial carcass weight and carcass composition of heifers placed (Dri feed in trials 2 and 3. Pre-trial nutritional and management pi“ocedures were kept as constant as possible for the three trials. F“inal Slaughter Procedure and Carcass Evaluation Trial 1 steers fed the high grain ration were slaughtered when 80% of the steers were estimated to grade choice. Steers fed 92 high silage were slaughtered when their mean weight was similar to the final weight of the high grain steers. All steers within a given energy level were slaughtered at one time. Trial 2 and 3 cattle were slaughtered in three groups, again based on an estimated degree of fatness sufficient for the choice grade. Fifty percent of the high grain fed steers per cattle type were slaughtered initially followed by the remaining high grain steers and 50% of the cattle fed high silage. The final slaughter group con- sisted of all remaining cattle. Heifers weighed approximately 85% of their steer mates at slaughter. All cattle killed initially and a total of 36 final slaughter steers (five high silage and four high grain steers per type) from trials 2 and 3 were slaughtered at the university meats laboratory. The pituitary gland and the semitendinosis (ST) muscle from the left side of the carcass were removed immediately after exsanguination of the 36 final slaughter steers. ST muscles were analyzed for moisture, fat, protein, nucleic acids, and muscle protein fractions and pituitary glands were assayed for total growth hormone content in studies by EVersole (1978). All trial 1 steers and the remaining trial 2 final slaughter ariimals were transported 105 km to a commercial packing plant (Walters packing Plant, Coldwater, Michigan) and processed by standard proce- dLJres. In trial 3, the remaining final slaughter animals were t1“ansported 160 km to a commercial packing plant (Dinner Bell Meats, Archbold, Ohio) for slaughter. 93 Carcass data were collected in a like manner regardless of slaughter location. Hot carcass weights were obtained and carcasses were chilled for a minimum of 24 hr preceding evaluation. Complete carcass quality and yield data were collected and actual fat thickness between the 12th and 13th rib was measured. Procedures for Determining Body Composition Body composition of all trial 1 and 2 experimental animals was determined by chemical analysis of the 9—10-11 rib cut as outlined by Hankins and Howe (1946). The rib section was removed from one side of the chilled carcass and immediately transported to the university meats laboratory for further processing. Ribs were subsequently separated irito bone and soft tissue. The soft tissue was passed through a Hobart ineat grinder (0.47 cm plate) five times and thoroughly mixed. A 1 kg subsample was secured and frozen for subsequent analyses. Rib tissue was analyzed for moisture by drying a 6 to 7 9 sample at 100 C for 24 fir. Nitrogen determinations were conducted on wet 1 9 samples with a Technicon Auto—Kjeldahl System. Ether extract was determined on dried samples with the Goldfisch procedure. Equations relating composition of the rib cut to carcass composition are presented in Table 11. Body composition of cattle slaughtered initially in trial 3 was determined by rib analysis as previously described. The compo- Sition of final slaughter animals was determined by the specific gravity technique outlined in Garrett and Hinman (1969). Carcass .3 .umm mmmucmo .13 w. ”do ”a .cemaoca mmmogmo "no flux .uzmwmz mmmogmo wxum>mcm owmwowam “um ”meowumw>wtnn< a .mpuuoo cwpcmampm meuwcw rpm we :owuwmanou ouma—a>m op vow: mm: weavwoocn uzu awe FP1OF-m ween Ammmpv .H1.mw “Hotcaa Ammmpv .3 u “pattau via :wmm 3mcmcm um» + cwmm xmtwcm :wwuoca Amx\_aoz som.mVAmx .coauwmoawv new wamov Amx\—auz www.mVAmx .zowuwmoawc :mwuosa speaov . ummm co mama duo Fatut=_ 33338 _amu_=fiv - Ado _actt “V338 Faewav umww co mama flag _a333=_ 33338 Pneumcev 1 flag Facet 33338 Facade zmv\_woz .cwmm xmcmcw pouch AmU\—muz .cwmm amtwcw you xcu\~muz .cmmm xmcmcw :wmuocm >cc\ux .comummoawv and xmv\mx .cowuwmoawv :wmuoca monastomtm mmmotmu m.N._ Amwapv cascw: use uuwgemo em .me.omm 1mm.nmm we» mwmocmo n9 Aaoapv ensue: use upmttaw mN.o Anm.wp -wm .o.ONv :wmuota mmmotmo A.nEmu mmmogmu a qumz Low :owuqugOUVfiON: cw 39 -L_o cm 30V t_a :3 :8 am xu_>atm owuwuwmm m AnemFV ozo: wen w:_xco: Nw.N + 355. new mmmogmu Amewpv 0302 use mcwxca: wm.m + xmo. :mwuoga mmmugmo Aeumwtepoav cowuoatuxa Locum .- Axe out 3:0 are 33-o_-¢ —;mupmnx 11 Axv :wmuota use amt FF-op1m Ameapv 830: new meexea: 3:0 at; 33-o_-m ~._ wtszUOLa to mmucwgmmwm acomumsam Ewu~ upmwck oucmELowcma uzo :owuwmoneou mmuugmu mcvcwECmumo Low mcompmacm wen mwgzvmoota .—— m_amh 95 weights were obtained on the chilled carcass in air and under water. A steel tank, 112 cm in diameter and 183 cm in height, was fitted with a Toledo triple-beam balance. The tank was filled to near capacity with water and temperature maintained at 10 C or less with crushed ice. The front and rear quarter of one side of each carcass was alternately suspended from the balance and immersed underwater and the weight recorded. Care was taken to insure that all air pockets in the carcass were removed. Carcass and water temperatures were obtained periodically and recorded for later use in the calculation of correction factors. The equations used to relate carcass density to carcass pro— tein and fat composition are outlined in Table 11. Carcass Performance Calculations Equations used to calculate carcass protein, fat, and energy gaivi for the three trials are presented in Table 11. The caloric valtJes of 5.686 Mcal/kg for protein and 9.367 Mcal/kg for fat tissue presented in Garrett (1958) were used. Economic Analysis The procedures outlined by Black and Fox (1978) and Crickeniberger and Black (1976) were followed in constructing the econonric framework. Total costs per 100 kg gain were calculated based on the ioooled performance results of the 2-year steer—heifer (all fed high Si lage) and 3-year high silage y; high grain steer comparisons. Nonfeed costs were allocated on the basis of frame size, where applicable, and reflected current price relationships (Table 26)’ 96 Feed costs were calculated at three corn prices: $7.86, $14.73, and $21.61 per 100 kg. The price of corn silage (ton basis) was defined as: 6 (price of corn grain $/bu) + $3.50 'Thus, corn silage was assumed to contain 6 bu of corn grain/ton and vvas priced to yield equal earnings per unit land as grain production (Woody and Black, 1978). Historically, the price of soybeans (per bushel) has averaged 2.35 times the price of corn ($/bu). Thus, the price of soybean meal vvas derived from the relationships between prices of soybeans and corn aiid among the prices of soybeans, soybean meal, and soybean oil. The (derived soybean meal price was based upon 48 lb of meal and 11 lb of O‘il from 60 1b (1 bushel) of soybeans: Stoybean meal = Soybean price - 11 (oil price/lb) + processing charge/bu (44%). $/lb 48 Scaybean oil is priced at $0.20/lb when corn is $2/bu, increasing $0.05 pear $l/bu rise in the corn price thereafter. A processing charge of $().35/bu was assumed. The derived price was increased 10% for pricing SCbeean meal 49 and $30/T was added as a transport charge. Mineral and vitamin components of the respective rations were Dr‘iced at current levels. Further assumptions involved in the cost ahalysis are presented as footnotes to Tables 27 and 35 for the high Silage steer yg heifer and high silage y§_high grain steer comparisons, 1‘espectively. 4_J 97 Analysis of Data General Statistical Procedures Statistical tests were designed in the context of research objectives, information from previous research, and biological modeling. The two general tests utilized in testing hypotheses for all trials are outlined in this section. The specific approaches and linear models used to estimate parameters are presented subsequently for the cow-calf, metabolism, and feedlot phases of the research. Additional details describing the analytical procedures may be found in Black and Harpster (1978). In all trials, the method of least squares (Siber, 1977; Rao and Miller, 1971; Searle, 1971) was used to estimate parameters of equations with the form: K Y1 = 2 B X .+e.. k=1 k k,1 1 Cattle type (USH, SH, AHC, AHH), year, and energy level (in the case of the metabolism trials and cow-calf trial 2) were treated as 0, l vari- ables, i.e., type, year, or energy level equals "1" if true, ”0" otherwise. For the feedlot trials, percentage concentrate in the ration, hot carcass weight and percentage carcass fat were treated as continuous variables. Two general types of hypotheses were tested. Tests used were: Test 1 The significance of main effects and interactions (for example, cattle type) were assessed as follows: HA: HN not true. Where: 8, ... B4 are parameters for the USH, SH, AHC, and AHH cattle types, respectively. Test statistic: (RSSE- URSSE)/r URSSE/UEDF is distributed as Fr’ UEDF. Where: RSSE is the error sums of squares for the "restricted” model (one intercept term for all cattle types); URSSE is the error sums of squares for the "unrestricted” model (a separate intercept term for each cattle type); UEDF is the error degrees of freedom for the unresticted model; and .5 is the number of restrictions imposed. 99 ZEEELE. Where a significant (P < .10) effect of cattle type was noted (as outlined in test 1) specific type comparisons of interest were conducted. Type comparisons included: USH y§_SH; SH y§_AHC, and AHC y§_AHH. Hypotheses were tested as follows: K H 2 Ck Bk = 9 (for example, 81- 82 = 0 for comparing k=1 two cattle types; i.e., C,= 1, C2: —1) N: HA: HN not true. A _ A 2 A A A V() — 13§V(B,)+CZV(82)+ZC,C2 COV(B,,82) Test statistic: A -AL:Q—— is distributed as to N- K ¢V($) Calculated levels of significance were reported in the tables for .005313s.20 as suggested by Black and Fox (1977). Values above the 10% level are presented so that other investigators can combine the results with results from similar independent experiments to PErmit evaluation of significance levels for the combined information. 100 For example, four similar independent trials, each with a significance value of .10, have a joint significance level of .03 when the results are pooled (Black and Fox, 1977). For purposes of discussion in the present studies, a "significant difference" for a given parameter was assumed if the significance level was less than .10. Cow—Calf Trials Experimental design of cow—calf trials 1 and 2 differed and thus data were analyzed independently. Least square means were estimated by the following linear models: Trial 1: Cow and calf performance parameters = f (cattle type); and Trial 2: Cow and calf performance parameters = f (cattle type, energy level). Since all animals within a cattle type (trial 1) or cattle type x energy level combination (trial 2) were group fed, feed intake and efficiency of feed utilization data could not be subjected to statistical analysis. Metabolism Studies Metabolism trial design was consistent in each of two years and data were pooled. Least square means were estimated by the linear model: Feed utilization parameters = f (cattle type, energy level, year). 101 Feedlot and Body Cpmposition Studies As previously outlined, USH, SH, AHC, and AHH steers were fed high silage (HS) and high grain (HG, 60% concentrate in trial 1, 80% in trials 2 and 3) rations in each of 3 years. Additionally, heifers of each cattle type were fed HS in trials 2 and 3. Data were organized in two comparisons: HS heifers y§_HS steers (2 year comparison) and HS steers y; HG steers (3 year comparison). The effects of sex on feedlot performance and carcass charac- teristics were examined in a comparison of HS steers y; heifers. Cattle type effects were not examined in this comparison due to the differences in selection criteria practiced for USH y§ SH, AHC, and AHH heifers as described previously. Carcass data and other parameters, where appropriate, were adjusted to the mean carcass fat of all steers and heifers in the comparison (29.2%). The effects of cattle type and ration energy level were examined by comparing HS y; HG steers. Steers were compared at similar carcass fat to examine the effect of cattle type on carcass characteristics. This adjustment was made to facilitate comparisons among types and to assess differences in fat distribution (marbling, KPH, external fat) had all steers been slaughtered at the mean carcass fat of 32.2%. Additionally, carcass data of steers was adjusted to a similar carcass weight within type to examine the influence of ration energy level on carcass characteristics. Specifically, this adjustment was made to ascertain differences in carcass fatness and quality when steers fed HS and HG are slaughtered at similar weights. ' .5- ”=03: 102 In both comparisons, equations for dry matter intake (DMI), feed/gain (F/G), and other parameters based on group data were estimated using treatment means since animals were not individually fed. Average daily gain (ADG), carcass protein gain, fat gain, and energy gain and carcass characteristic equations were estimated using individual animal data. Analyses indicated that year x cattle type and year x energy level interactions were not significant. Thus, these parameters were not included in the final models utilized to estimate treatment means. However, an energy level x cattle type interaction was noted in the HS y; HG steer comparison for F/G. Thus, terms recognizing this inter- action were included in the F/G model. Specific linear models used to calculate treatment means were as follows: 1. HS steers y§_HS heifers: A. Dependent variables = f (cattle type, sex, year) Where dependent variables are: DMI ME intake ADG F/G Crude protein intake Efficiency of crude protein utilization for carcass protein production Efficiency of ME utilization for production of edible portion B. Depepdent variables = f (cattle type, sex, mean carcass fat, year 103 Where dependent variables are: Carcass characteristics Carcass protein gain, fat gain, energy gain Edible portion gained Energetic efficiency II. HS steers y§_HG steers: A. Dependent variables = f (cattle type, percent concentrate, year) Where dependent variables are: DMI MEI Crude protein intake Efficiency of crude protein utilization for carcass protein production Efficiency of ME utilization for production of edible portion B. ADG, carcass characteristics = f (cattle type, percentage concentrate, hot carcass weight, year) C. Feed/gain = f (cattle type, percentage concentrate for non— Holsteins, percentage concentrate for Holsteins, year) 0. Dependent variables = f (cattle type, percentage concentrate, mean carcass fat, year) Where dependent variables are: Carcass characteristics Carcass protein gain, fat gain, energy gain Edible portion gained Energetic efficiency In the case of the HS y§_HG steer comparison, percentage concentrate in the ration was included as a continuous independent variable since three levels of concentrate were compared: 9% for HS rations, 60% concentrate and 80% concentrate (HG rations). A weighted average concentrate value (71%) was used to calculate least square means for cattle fed HG. RESULTS Cow-Calf Trial 1 Weight and Condition of Cows Mean weight and external fat changes of trial 1 cows are presented by weigh period (28 days) in Figure l. Cows were placed on experiment in early December and during the adverse weather conditions encountered during the winter months, most cows lost body weight and condition. Average temperature (C) and wind speed (km/hr) for the months of December, January, and February were —2.2, 15.8; —7.2, 19.0; and O, 20.1, respectively (Table A.5). By early April, average weight loss was 20, 31, 51, and 68 kg for USH, SH, AHC, and AHH cows, respectively. Since the calving season extended from January 22 to April 7, 1976, part of the weight loss can be attributed to calf weight and fetal tissue loss. However, average external fat cover in early April was less than 0.25 cm for all groups, indicating a mobilization of fat stores in an attempt to meet energy requirements. All cows gained in weight and condition during sub- sequent months after the lactation ration offered was increased 25% on April 7, 1976 (day 112). Mean initial, final, and amount of change values for cow weight and condition are presented in Table 12. SH cows were heavier (P= .05) than USH and lighter (P= .07) than AHC cows initially while AHC and AHH 104 EXTERNHL FHT (CM) BUDYWEIGHT (K01 105 300 Figure 1. N # 0'3 era-(- 5“ PERIOD [28 DRYS] I l I I J l I I I I I I T I 6 8 10 DRYS] 2 4 PERIOD (28 Mean weight and external fat changes of Unselected Hereford ([11), Selected Hereford (X), Angus x HerefordxCharolais (A), and Angus x Hereford x Holstein (316) cows (trial 1 Table 12. Effect of Cattle Type 106 on Cow and Calf Perfonnance (Trial l)a Cattle type b Significance level Type comparisonsc USH y; SH y; AHC y; Item USH SH AHC AHH SE Cattle type SH AHC AHH No. of cows 8 9 10 8 Cow wt initial, kg 374.8 431.4 480.4 486.2 26.9 <.005 05 .07 20 Cow wt final, kg 413.3 457.6 481.3 460.7 30.7 >.20 NA NA NA Cow fat initial, cm 0.24 0.45 0.41 0.33 0.10 .18 NA NA NA Cow fat final, cm 0.32 0.38 0.41 0.32 0.10 >.20 NA NA NA Cow wt change, kgd 38.6 26.2 0.91 -25.5 17.9 .01 20 .17 17 Cow fat change, cmd 0.08 -0.07 0.0 -0.01 0.11 >.20 NA NA NA Calf birth wt, kg 29.1 36.4 39.4 39.5 3.2 .01 03 >.20 > 20 Adj. calf weaning kge 161.5 193.8 208.2 228.9 19.3 .02 12 > 20 > 20 Preweaning calf 6, kg 0.65 0.77 0.82 0.92 0.08 .03 17 >.20 > 20 aLeast square means and standard error of the difference between two means (SE). Maintenance and lactation levels of energy were based on National Research Council (1970) reconnendations. b USH: Unselected Hereford; SH: AHH: Angus x Hereford x Holstein. Selected Hereford; AHC: Angus x Hereford x Charolais; cNA: Comparison not appropriate (main effect of cattle type not significant at P< .10). dFinal minus initial values. 8Adjusted for age of dam, sex of calf, 205 day basis. fBased on adjusted weaning weights, 205 days. 107 cows were similar. Final weights did not differ (P >.10) by cattle type and of the specific type comparisons examined, there were no significant differences (P >.10) in body weight change for the 280 day trial. All cows gained weight over the duration of the trial except AHH cows, which lost an average 25.5 kg. Initial body weights of USH, SH, and AHC cows, expressed as a percentage of AHH cows, were 77, 89, and 99%, respectively. Similarly, calculated values for final weight were 90, 99, and 104%, further emphasizing the relatively poor ability of AHH cows to maintain their body weight. Initial and final body condition, as measured by external fat cover, was not different (P >.10) among the four types of cows. Aver— aged over cattle types, initial and final values were 0.36 cm. Thus, although not noted with body weight, external fat was fully recovered during the 280 day trial. Preweani ng Cal f Performance Birth weights of SH, AHC, and AHH calves were similar (Table 12). Predictably, USH calves were lightest at birth and weaning. Adjusted 205 day weaning weights increased with increasing frame size as did preweaning calf average daily gain. There were no differences (P >.10) l'n calf weaning weight or ADG for USH y; SH, SH g AHC, or AHC E AHH Calves. However, if the average framed British breed calves (SH) are taken as reference animals, USH calves gained 16% slower, AHC calves 6.5% faster and AHH calves 19% faster to weaning. 108 Cow Intake and Efficiency of Producing Calf Weaning Weight Cows within a cattle type were group—fed and thus intake and efficiency data could not be subjected to statistical analysis. However, apparent trends will be pointed out. Cows were fed according to requirements (NRC, 1970) based on body weight and thus TDN and dry matter intake increased with increasing cow weight (Table 13). Since maintenance requirements are a function ()f metabolic body size, TDN intake was also expressed on that basis. Differences were small ranging from 57.6 to 62.8 g TDN/Wkgs/day for IXHC and USH cows, respectively. It was not possible to separate calves from cows at feeding 'time and thus an unknown amount of feed was consumed by the calves. Twonetheless, efficiency of conversion of total TDN consumed by the cow- (:alf unit to calf weaning weight can be calculated. This measure of erfficiency increased as cow size increased (Table 13). Trends were 5 imilar when TDN intake and TDN/calf WW were projected for a full year. lliis is a more realistic evaluation of the energy costs of producing CEllf weight since the cow must obviously be maintained throughout the ywearn NRC (1970) requirements for maintaining dry, pregnant cows at 'theair off-experiment weights were used in estimating the 85 days of feed required to complete the year. Again using the average frame BPi‘tish breed cows (SH) as reference animals, USH cows required 14% morwe TDN to produce a unit of weaned calf. AHC and AHH cows required 95 arid 91% as much TDN as SH cows to produce a unit of calf weaning WEight. 109 Table 13. Mean Daily Dry Matter and Total Digestible Nutrient Intake of Trial 1 Cows and Efficiency of Feed Utilization for Production of Calf Weaning Weighta Cattle typeb Item USH SH AHC AHH No. of cows 8 9 10 8 "Trial basis, 280 days Dry matter intake, kg/day 7.93 8.34 8.44 9.07 TDN intake, kg/dayc 5.55 5.84 5.91 6.35 Cowkgsd 88.43 96.81 102.63 101.51 TDN intake, g/Wkgs/daye 62.8 60.3 57.6 62.6 TDN/calf wwf 9.62 8.44 7.95 7.77 Yearly basis, 365 daysg TDN intake, kg/day 5.01 5.29 5.39 5.68 TDN/calf ww 11.33 9.96 9.44 9.07 aMaintenance and lactation levels of energy were based on National 12esearch Council (1970) recommendations. Lactation ration amounts were ivicreased 25% on day 112 of the trial and continued for the remainder 0f the trial. bUSH: Unselected Hereford; SH: Selected Hereford; AHC: Angus x Heereford x Charolais; AHH: Angus x Hereford x Holstein. CCalculated ration total digestible nutrients (TDN), 70.0%. dAverage of initial and final values. eAn unknown amount of feed was consumed by the calves which were "01: separated from the cows. _ fObserved total feed TDN intake of cow and calf (kg) per kg adJusted calf weaning weight (WW). _ gObserved TDN intake plus recommended amount of TDN required to mairitain dry, pregnant beef cows at their off-experiment weights for an additional 85 days. 110 Rebreeding Performance As previously indicated, the amount of lactation ration offered vvas increased on day 112 (April 7) of the trial with cows inseminated on days 163 and 164 (May 28 and 29, 1976). Although cows were gaining vveight at the time, only 15 (42%) were cycling when inseminated, as defined by serum progesterone levels greater than 1.0 ng/ml (Table 14). Fifty-three percent of all cows cycling became pregnant. The percentage of all cows cycling and the percentage bred of those cycling were, respectively: USH, 56, 80; SH, 22, 0; AHC, 30, 33, and AHH, 63, 60. Definitive conclusions concerning cattle type differences in ability to rebreed under the nutritional and environmental conditions imposed are limited due to the small number of cows per group and variation in the length of time from calving to rebreeding. For example, AHH cows tended to calve early and therefore had a greater time period to resume normal cycling. Cow-Calf Trial 2 Weight and Condition of Cows In trial 2, five cows per type received a low (NRC) and five C(MNS a high (NRCi-25%) level of energy based on the revised maintenance arici lactation requirements recommended by NRC (1976). Mean 28 day body weeight and external fat values for the USH, SH, AHC, and AHH cows are Drwasented in Figures 2 to 5, respectively. External fat cover of AHH Covvs was lowest at the beginning of the trial and remained less than the other cattle types throughout the study, especially those fed the 111 Table 14. Rebreeding Data for Trial 1 Cowsa No. of No: b No.c Avg. days Cow type cows cycl1ng bred postpartum Unselected Hereforde 9 5 4 86 Selected Hereford 9 2 0 76 Angus x Hereford x Charolais 10 3 l 84 Angus x Hereford x Holstein 8 5 3 100 aProstaglandin F20 was used to synchronize estrus. bSerum progesterone levels 2 1.0 ng/ml. CTwo of the eight cows bred conceived to a return service. dAt time of breeding. eOne Unselected Hereford cow was lost after completion of the rebreeding phase of the experiment. 112 E L) p.- (I L _l c: 2 a: LIJ ..— >< LL] 2- PERIOD [28 DHYS) 600+ 8 500-» S: }_ . a: 53 Si] 400.. )_ a O m .1,. 300 i 1 i i : 1 1 4 i 4%. 0 2 4 6 8 10 PERIOD (28 DRYS) Figure 2. Mean weight and external fat changes of trial 2 Unselected Hereford cows fed two levels of energy (NRC: [E]; NRC+25%: X). 13.5—awn” EXTERNRL FHT [CM] BUDYWEIGHT (K01 113 -r 0 1 441 1 1 1 1 1 444 .1 1 1 2 4 6 8 10 PERIOD (28 DHYS) 6001- -r .5002 400 - 300 1 1 1 1 1 1 1 1 1 1 2 10 A a PERIOD (28 Dave) Fl gure 3. Mean weight and external fat changes of trial 2 Selected Hereford cows fed two levels of energy (NRC: [I]; NRC +25%: X). 114 .80’ Z O .—— C: H. _J CE 2 CK Ll-J ’— X LL] .201» 0 i i 1 i 5 41 i 1 i i I 0 2 4 6 8 10 PERIOD (28 DRYS] 6001’ C) 500.. x F— 1* I C) H UJ 400 - z >— D D m .- 300 1 *‘r i 1 i 1 i i i i 0 2 6 8 10 Z PERIOD (28 DRYS] F1'Slure 4. Mean weight and external fat changes of trial 2 Angus x Hereford x Charolais cows fed two levels of energy (NRC: E]; NRC +25%: X). 115 v- .80" I: Q 41» 5— . 60" CI “- it _I (I Z .40: (K m ‘P .- x m I20 ‘_ 0 i it 4;- i 1 % 1' i i 1 i O 2 4 6 8 10 PERIOD [28 URYS) 600" ) c) 500! K I— -> I CD u—a UJ .. I: 400 >_ D CD m .. 300 *1; i i 4 41* 1‘ 3‘ i i 1 1‘ 0 2 4 6 8 10 PERIOD (28 DRYS) Figure 5. Mean weight and external fat changes of trial 2 Angus x Hereford x Holstein cows fed two levels of energy (NRC: [I]; NRC +25%: X) _— s ...-n-/' 116 low energy level. Environmental conditions were more severe in trial 2 than trial 1. Mean temperature (C) and wind speed (m/hr) for the months of December, January, and February were -7.8, 17.2; -1l.8, 19 8, and -5.3, 18.3, respectively (Table A.5). As in trial 1, cows were main- tained outside without shelter although they were moved to a sheltered area for calving. Mean body weight and external fat changes for the duration of the trial are presented in Table 15. As noted in trial 1 final body \Neight did not differ (P> .10) for USH y§_SH, SH y§_AHC, or AHC y§_AHH cows. However, averaged across cattle types, final weights were heavier (P< .005) for cows fed high y§_low energy (413 y; 504 kg). Cow weight change for the 301 day trial did not differ by cattle type (P> .10) but favored the high energy groups (-17 y§_-83 kg). Initial external fat values were similar across groups of cows ‘Fed low and high energy but averaged less (P= .06) for AHH y§_AHC cows. Final and final minus initial fat values were not influenced by cattle ‘type although both values were lower for cows fed low energy. In summary, cows receiving the low energy level regained 83% of their initial body weight and 48% of their initial condition. Cows receiving the high energy level regained 97% of their initial body weight and 82% of their initial condition. Preweaning Calf Performance Calf birth weight was not influenced (P> .10) by the level of energy fed to the cows (Table 15). Trends among cattle types were 117 ewecec—Sues we 32 .5312. x egocecwz x mzmc< .mwmee ace mON .wpeu we xem .Eee we woe Lew eeumene< .mxee mON .mucowwx mc_cme3 emumemee ce eomemu .Aop. v2 um aceuwmvcmwm uec oexu w—uaeu we “emcee cveev ”:2< "220.85 x ecececo: x meoc< uux< mecewwgm: ewuuw—mm .mwumz "camumuum— _ucm wucacwucwg Low xmLocw ho m—w>w— $092955.qu Acuas .33 weave e5 5953 wececeute 93 we cote w .33: Err—E meet: _ecIe 32.39.32 uec ceflceeeeu “<2 e "2m "econ—ecu: ewuewpemc: ”239 7558 53.32. 3:332 522 ._e>o_ a ecmeceum ecu acne... 9.26m 33.—e 8; $6 2d N26 mNuxz me. No. 8. A mee.v co. 86 8.0 mud Nee $6 922 mm; .22 :3 mcwcmexecc TSN ..eNN 78— 99: 38.2 me. me. 8.x mee.v 8. m4: weNN m.SN «:3: N52 922 2.9. J: acmcewx :8 ._.e< oNc 2.; mNc N.nm m~e<2 8.x eN.x mee.v 399 8.x m.N N22 mew 5:2 eNm 922 3 J3 522 :8 861 2.01 2.01 2.01 38.2 <2 <2 <2 8.x mee.v 86 $6. 3.0- 3.0- end- 82 web .855 an.— 33 méN- w.nN1 map- m.n- mNumz <2 <2 <2 8.x 39v me— wéo- 5mm- 2.;- ede- 922 was. .wmcece a: 38 9.0 med 86 $6 mNuxz <2 <2 <2 5. m8.v 86 «N6 Nd and one ....22 .5 .22..» an» 38 3.0 $6 Ed Ed 382 we. eN.x ONX we. oN.A 26 $6 $6 2.0 36 em: .5 :2...ch use :8 9me m.mNm 2.23 To: mNuzz 8.x 3.x 9. we. moo.V YNM TNNQ 2.7.3 93... eNon Q22 9. ..ucC «3 38 u .ONm N .ovm m .vem m .2; mNumz 8.x 3. mo. 8. eN.A e.em 93m «.23 meow mNmo u22 9. .2335 a: :8 c m m e «.822 e m c m 922 4.3 we .02 122< le:< 12m 8.3 2:6— wm 22< uz< 2m 2m: 55— so: m> u:< m> 2m m> :m: 233 33cm 38cm avg» 233 a emcemtueeee we: mueotw c3: aAN 22.5 mocaEeucec :3 ecu :8 5 .33 280cm ecu 25. 238 we 38E .3 222. 118 similar to tria1 1 with SH ca1ves heavier at birth than USH ca1ves (P< .005) whi1e SH v§_AHC and AHC v§_AHH ca1ves did not differ (P> .10). Ca1ves from dams fed high energy were an average 12% heavier at weaning and gained 15% faster than ca1ves from 10w energy dams. Comparing catt1e types, adjusted ca1f weaning weight and pre— weaning gain increased with increasing frame size, a resu1t consistent with tria1 1. However, for USH and SH ca1ves, these va1ues were not different (P> .10). Cow Intake and Efficiency of Producing Ca1f Weaning Weight Dry matter and TDN intake were determined by cow weight and increased according1y (Tab1e 16). AHH cows, however, received 1acta- tion 1eve1s of energy recommended by NRC (1976) for cows of "superior rni1king abi1ity.” At a given body weight, approximate1y 25% more TDN is recommended for cows of superior v§_average mi1king abi1ity. Thus, 'TDN intake per unit metabo1ic body size was essentia11y equa1 for USH, SH, and AHC cows whi1e consumption by AHH cows was greater. The 1ower (energy intake (per unit metabo1ic body size) of tria1 2 high energy cows (USH, SH, AHC) re1ative to tria1 1 cows is exp1ained by two factors. First, tria1 2 was conducted over a 1onger period of time preca1ving, thus, more days on a maintenance ration. Second1y, the revised feeding standard fo11owed in tria1 2 (NRC, 1976), whi1e increasing pregnancy requirements re1ative to tria1 1 recommendations (NRC, 1970), actua11y decreased 1actation 1eve1s approximate1y 10% for cows of average mi1king abi1ity. 119 Tab1e 16. Mean Dai1y Dry Matter and Tota1 Digestib1e Nutrient Intake of Cows Fed Two Leve1s of Energy and Efficiency of Feed Uti1ization for Production of Can Weaning Weight (Tria1 2) b Energya Catt1e type Item 1eve1 USH SH AHC AHH No. of cows NRC 5 4 3 4 NRC25 4 5 5 4 Tria1 basis, 301 days Dry matter intake, kg/day NRC 6.01 6.48 6.80 7.81 NRC25 7.45 8.38 8.74 10.08 TDN intake, kg/dayC NRC 4.21 4.54 4.76 5.47 d NRC25 5.22 5.87 6.11 7.06 Cow ”R75 NRC 90.36 97.05 107.71 98.19 9 NRCZS 94.02 106.29 110.00 109.13 TDN intake, g/Nk75/daye NRC 46.6 46.8 44.2 55.7 9 NRC25 55.5 55.2 55.5 64.7 TDN/ca1f wwf NRC 8.01 8.07 7.11 7.26 NRCZ5 8.69 9.25 8.21 8.52 Year1y basis, 365 days9 TDN intake, kg/day NRC 4.02 4.32 4.59 5.09 NRCZS 5.06 5.70 5.90 6.70 TDN/ca1f ww NRC 9.28 9.31 8.32 8.20 NRCZS 10.20 10.89 9.61 9.80 aNRC: Nationa1 Research Counci1 (1976) recommended 1eve1$ of energy for maintenance and 1actation; NRC25: 125% of recommended 1eve1s. AHH cows were fed at the 1eve1 recommended for cows of superior mi1king abiTity. bUSH: Unse1ected Hereford; SH: Se1ected Hereford; AHC: Angus x Hereford x CharoTais; AHH: Angus x Hereford x Ho1stein. CCa1cu1ated ration tota1 digestib1e nutrients (TDN), 70.0%. dAverage of initia1 and fina1 va1ues. eAn unknown amount of feed was consumed by the ca1ves which were not separated from the cows. fObserved tota1 feed TDN intake of cow and ca1f (kg) per kg adjusted ca1f weaning weight (ww). gObserved TDN intake p1us recommended amount of TDN required to maintain dry pregnant beef cows at their off—experiment weights for an additiona1 64 days. —3-——'—* . “‘7 120 Tota1 TDN consumed during the tria1 per unit ca1f weaning weight produced favored the 1arger cows (Tab1e 16), as noted in tria1 1. When projected over a fu11 year, efficiency was highest for AHH cows and Towest for SH cows. Averaged over a11 catt1e types, 15% more feed was required by the high vs 10w energy cows for production of a unit weaning weight. This was noted despite a 12% heavier weaning weight for high energy ca1ves. Metabo1ism Studies Nitrogen Uti1ization As indicated in Tab1e 17, metaboTism data are the pooTed resu1ts of two tria1s. Mean initia1 body weights of the USH, SH, AHC, and AHH steers used in these tria1s were 171, 227, 243, and 278 kg, respective1y. Steers were fed ag_1ibitum throughout the tria1s and nitrogen intake ref1ected frame size differences (Tab1e 17). SH steers consumed more nitrogen than USH steers (P< .005) and AHH steers consumed more than AHC (P= .04). Steers fed HG rations consumed more (P< .005) nitrogen than those fed HS (148.5 y§_129.3 9). There were no differences in feca1 nitrogen excretion among steers fed HS vs HG rations. Coup1ed with the higher intakes of HG steers, this indicates a more comp1ete digestion of the ration nitrogen for steers fed HG v§_HS (66.8 v§_58.5%). Differences in digestibi1ity due to catt1e type were apparent1y sma11. Apparent digestibi1ity of HS nitrogen for USH, SH, AHC, and AHH steers was 58.6, 57.2, 58.4, and 121 .mpuwcu e2» we goum cw cewuuc geue eu>wmeec max» cue mcemum ezpe .op. vc pu ucuewmwcawm uec waxy mFHuue we peewmu cwusv ouumcceceeu uec cemmcuesee ”<2 x ecomecm: x mewc< ”22< mmwupocucu x ecowecez x memc< ”u2< mecewwcez emuuepwm .pceEe—ecem ecu ccee 2cm m=_c wmqum ccee Rom .Ammv mcueE exp ceezumn mecocewmwe ecu we no: nucuempccam w:_u emufiwm cceu "m: e .cweum—ez "2m mecewmcm: eeuee—wmc: ”zmze a ceccu ecuecuum ecu mcuee ecuccm umuugu n.m2 «.22 o.m2 c.2m a: euccemeu <2 <2 <2 o~.A m_. m.n 2.02 m.em N.~m ~.m2 m: cemecpwc we pcwecmc 2.Nm e.m~ o.om 2.2m 2: <2 <2 <2 om.A No. m.2 o.2m N.—~ w.—N o.om m2 oxuucw cemecuwc we uceecuc N.2m u.m2 w.m2 _.m2 o2 <2 <2 <2 o~.A moo.v e.e m.mm m.mm m.m~ m.~m m2 2ue\m .eecmuuuc cumecuwz m.Fe m.em c.2m o.mm w: o~.A o~.A Po. moo.v mp. m.m 0.2m m.o2 2.22 2.2m m: 2ue\m .eeuucexe 2 ecmce ~.mm m.Nm ~.mm c.2m w: w_. o~.A moo.v moo.v mF. N.2 N.Nm m.mm P.2m m.wm m2 2ue\m .eeumcexo z Pueuu m.mm2 o.mmp e.mm_ o.~—— w: 2o. om.A moo.v moo.v moo. F.m n.2m— N.mmp 2.mmp 2.mm m2 2ueB .wxuucw cmmecuwz 2 2 2 2 emcmwum we .ez .122< 1M2< 112m e22» _w>wp mm 22< u2< 2m 2m: Pu>ep seem m> uz< m> 2m m> 2m: eFuuuu amcecm zucmcm umcxu epuuuu n emcemwcueEee e222 mueemwo cwuz umcewum Fuwcp Emwreauuez 22 cemecuwz we cewuu~w22u= ce _w>e2 22cm:m cewuum ecu we2p epuuuu we ueewmu .NF eFeu» 122 59.8%, respective1y. Simi1ar va1ues for steers fed HG were 69.3, 65.2, 66.1, and 66.5% for USH, SH, AHC, and AHH steers, respective1y. Urine nitrogen excretion f0110wed the same pattern noted for nitrogen intake a1though there were no differences (P >.10) between HS and HG steers. SH steers excreted more (P= .01) urinary nitrogen than USH steers whi1e remaining catt1e type comparisons were not significant (P>.10). Whi1e the grams of nitrogen retained dai1y increased with increasing steer frame size, differences were not significant (P> .10). Nitrogen retention expressed as a percentage of nitrogen intake or as a percentage of nitrogen absorbed, a1so did not differ (P >.10) by catt1e type. Energy 1eve1 effects were noted for severa1 measures of nitrogen retention. Steers fed HG v§_HS retained more (P <.005) nitrogen dai1y (47.1 v§_31.4 g), and retained a higher (P= .02) percentage of nitrogen intake (32.6 v§_24.2%). Apparent bioTogica1 va1ue of the HG ration tended to be higher than the HS ration (48.7 vs 40.9%), but the difference was not significant (P >.10). Energy Uti1ization Dai1y dry matter and energy intakes increased with increasing catt1e frame size (Tab1e 18). Energy intake was higher (P<:.005) for SH vs USH and AHH v§_AHC steers (P= .06). Averaged across catt1e types, dai1y energy intakes were 26.2 Mca1 for steers fed HS and 28.1 Mca1 for steers fed HG (P> .10). 123 .exuucm xmcece 2e 2w uu eeuuewume wee: memmor aocwce maoemuw .memme_ xmcuce meewmum ecu .2cucwce .Pueww mccws exuucw 23.55“F .mpuwcu eze we ceue c? cewuuc ceuu em>weeec maze emu mceeum ezhe .Ao—. vc uu ucuewmwcmwm uec e22“ eFuuue we uemwmw cmusv euu_ceeceuu uec chmwcucEee nup um 22< u2< 2m 2m: Fm>u_ 5622 m> uz< m> 2m m> 2m: e_uuuo 2mcecm nxmcecm 68.3 6 ES Tecemmcucsee wcxh muem$ee cwuz uncewum Fume» Emwpenuuez 22 xacwcm we ce2uuNmeu= ce Fo>m2 xmcmcm cewuux ecu weak epuuuu we uewmmm .wp epnuh 124 FecaT energy excretion was marked1y affected by energy 1eve1 of the ration (P< .005), and averaged 8.68 Mca1/day for HS and 6.53 Mca1/day for HG steers. Apparent energy digestion coefficients were thus 66.8 and 77.0% for the HS and HG ration, respective1y. SH steers excreted more (P< .005) feca1 energy than USH steers; other type com- parisons were not significant (P> .10). As previous1y noted with the nitrogen data, differences in apparent energy digestibi1ity were sma11 among catt1e types. Coefficients for steers fed HS were 66.7, 66.8, 66.6, and 67.2%; HG va1ues were 79.8, 76.4, 76.0, and 75.6% for USH, SH, AHC, and AHH steers, respective1y. Urinary energy excretion was simi1ar between the two rations and for SH, AHC, and AHH steers. USH steers, however, excreted 1ess urinary energy (P< .005). Energy retention was defined as energy intake minus feca1, urinary, and estimated gaseous energy 1osses and did not inc1ude an estimate of heat increment. Mean va1ues were 14.88 and 18.76 Mca1/day for the HS and HG ration, respective1y (P< .005). Of the catt1e type comparisons made, SH steers retained more (P< .005) energy than USH steers. Metabo1izab1e energy (ME) va1ues of the respective rations were not inf1uenced by catt1e type (P> .10). Mean va1ues for the HS and HG rations were 2.58 and 2.96 Mca1 ME/kg ration dry matter, respective1y, and were significant1y different (P< .005). 125 Feeding Tria1s: Steers vs Heifers Initia1 S1ayghter Catt1e Steer and heifer ca1ves fed an a11 si1age ration in tria1s 2 and 3 were uti1ized in the steer—heifer comparison. The average weights and carcass composition of the anima1s s1aughtered initia11y are presented in Tab1e 19. A sma11 number of heifers were avai1ab1e for initia1 s1aughter purposes, and initia1 data were app1ied across tria1s. The mean dressing percentage and carcass composition for each type and sex was used to estimate the initia1 carcass weight and com- position of catt1e p1aced on the experiments. In genera1, tria1 3 ca1ves were initia11y fatter and had higher dressing percentage than tria1 2 ca1ves. Intake, Gain, and Feed Efficiency Throughout discussion of the steer-heifer comparison (both fed HS), emphasis wi11 be p1aced on the main effect of sex. Statis- tica1 ana1ysis was not conducted to determine catt1e type differences because differentia1 se1ecti0n procedures were uti1ized in retaining rep1acement heifers. Thus, the qua1ity of the heifers avai1ab1e for the feed10t cou1d vary. SH, AHC, and AHH rep1acement heifers were saved each year on the basis of their unadjusted year1ing weight. USH rep1acements were saved without considering weight, but were in the same age groups as heifers retained in the other three groups. Thus, a1though differences in qua1ity of feed10t heifers were Tike1y .‘WAM 126 mmvupecucu x ecowmcez x mzmc< “oz< mecemmcwz eepem—em .cwmpmpez x ecowecm: x mcmc< ”:2< "2m megoyecm: ewuempmmc: "zmea .F ~u2cu c2 emy uec wee: mcmwwmzu 22.0N 22.22 _.mm 2.mm— 2.22N 2 mcwmpm 22< m2.2p om.m_ w.mm c.2m_ 2.m2N m mcmmpm QI< wN.wF oo.wp m.Nm m.mm m.mnp N mcm22m2 mm.m_ ww.2_ m.mm 2.mop 0.022 m mcmmpm 2m mm.w_ 2w.2_ m.mm m.mw m.omp m mcmmpm mm: m No.22 2w.22 o.mm m.wo_ m.2ON m mcmwwmz o~.2_ me.mp N._m m.mm2 N.N2N N memmum 22< 2m.mp mm.2p m.m2 2.2w 2.222 N mcmkwwz mm.m2 om.wp w._m o._m_ c.2mN m wcmmpm uz< m2.2_ oo.w_ m.w2 2.No_ 2.22N m mgmmpm 2m _o.mp oo.op 2.Nm m.m2 e.m2p m mcm22e2 om.NF om.w2 2.2m 2.0m 2.mo_ N mcumpm 2m: N.F 2 2 2 22 .23 22 .23 mpuewcu xum @222 uFuwch .2u .cwmpeca mc2mmmco mmuecuo 2czccm 2e .02 eFupuo mmuecuu mmuecuu n Am .N .F mpuwghv mpwguu cmpgmeupm PuwuwcH we cowawmoeeeu mmuecuo ecu .mpgmwmz mmueguo .m22m283 2c=csm .m— epnuh 127 sma11 among the groups, catt1e type comparisons were deferred to the HS v§_HG steer tria1s. Dai1y gain, intake, and feed/gain data are presented in Tab1e 20. Averaged across catt1e types, dai1y gains were 1.01 kg for steers and 0.85 kg for heifers, a difference of 0.16 kg (P <.005). Re1ative gains (g/Wkg5), however, were 12.1 and 11.9 g for steers and heifers, respective1y (P> .10). Dai1y dry matter intake of steers was 13% greater than for heifers (P< .005); however, on a re1ative basis, intake was higher (P= .02) for the heifers. Unadjusted kg of feed required per kg of gain was 5.4% greater (P= .02) for heifers v§_steers (8.66 vs 8.22). However, heifers were fatter than steers (30.1 v§_28.2% carcass fat) and this wou1d affect the feed/gain differences observed. Thus, the observed feed/gain va1ues were adjusted to the mean carcass fat (29.2%) of a11 catt1e in the comparison using the adjustment factor out1ined in Fox and B1ack (1977). Ana1ysis of the adjusted va1ues revea1ed no differences (P> .10) in feed/gain for steers v§_heifers, the additiona1 requirements of heifers being reduced to 2.3% (8.30 v§_8.49). Carcass Characteristics Carcass data are presented in Tab1e 21. Adjusted to simi1ar carcass fat (29.2%), steers and heifers did not differ (P> .10) in marb1ing score (10.4 and 10.3) or qua1ity grade (9.4 and 9.1). Steers had greater (P= .04) externa1 fat (0.97 v§_0.84). Differences in rib eYe area and kidney, heart and pe1vic fat were sma11 (P> .10) and numerica1 yie1d grades were Tower (P< .005) for heifers. 1228 Tab1e 20. Effect of Sex on Intake. Gain, and Feed Efficiency of Steers and Heifers Fed a High SiTage Ration b Significance Catt1e type 1eve1 Item Sex USH SH AHC AHH SE Sex No. of anima1s Steers 11 15 15 15 Heifers 13 14 15 15 DaiTy gain, kg Steers 0.91 1.00 1.05 1.07 0.02 .005 Heifers 0.75 0.84 0.90 0.91 g per ”k75 Steers 12.2 12.3 12.1 11.7 0.2 .20 9 Heifers 12.0 12.1 11.9 11.5 Dain dry matter intake,c kg Steers 7.12 8.11 8.65 9.22 0.14 .005 Heifers 6.15 7.15 7.69 8.26 g per ”275 Steers 96.0 99.4 99.1 100.8 1.7 .02 9 Heifers 99.5 102.8 102.5 104.3 Feed/gain Steers 7.80 8.10 8.24 8.72 0.22 .02 Heifers 8.25 8.55 8.69 9.16 Feed/gain, adjustedd Steers 7.86 8.28 8.47 8.57 0.25 .20 Heifers 8.05 8.47 8.66 8.76 aLeast square means and standard error of the difference between two means (SE). bUSH: Unse1ected Hereford; SH: AHH: Angus x Hereford x Ho1stein. cIntake of corn si1age dry matter was increased 6.8% to adjust for errors in dry matter detenmination. Se1ected Hereford; AHC: Angus x Hereford x CharoTais; dFeed/gain va1ues adjusted to the mean carcass fat (29.2%) of a11 catt1e in the comparison. Adjustment factors out1ined in Fox and B1ack (1977). 129 Tab1e 21. Effects of Sex on Carcass Traits of Steers and Heifers Fed a High Si1age Ration Hhen Catt1e Here Adjusted to Simi1ar Carcass Fata b Significance Catt1e type 1eve1 Item Sex USH SH AHC AHH SE Sex No. of anima1s Steers 11 15 15 15 Heifers 13 14 15 15 Carcass wt, kg Steers 267 302 332 348 Heifers 212 250 265 284 Carcass fat, % 29.41 28.49 27.98 30.76 Marbiingc Steers 9.7 10.2 10.7 11.1 0 8 >.20 Heifers 9.6 10.1 10.6 11 0 Qua1ity graded Steers 9.0 9.2 9.6 9.6 0.4 >.20 Heifers 8.7 9.0 9.4 9 3 Externa1 fat, cm Steers 0.94 0.99 0.91 1.04 0.08 .04 Heifers 0.81 0.86 0.76 0.91 Rib-eye area, sq. cm Steers 71.70 72.69 78.47 76.02 1.92 >.20 Heifers 71.86 72.85 78.63 76.19 KPH, % Steers 2.2 2.3 2.6 2.6 0.1 >.20 Heifers 2.2 2.4 2.6 2.7 Yie1d grade Steers 2.6 3.0 3.0 3.2 0.1 < .005 Heifers 2.0 2.4 2.3 2.6 aLeast square means and standard error of the difference between two means (SE). Carcass traits were adjusted to the mean carcass fat of a11 catt1e in the comparison (29.2%). bUSH: Unse1ected Hereford; SH: Se1ected Hereford; AHC: Angus x Hereford x Charo1ais; AHH: Angus x Hereford x HoTstein. cS1ight+ = 9; sma11-=10;sma11 =11. dHigh good = 9; 10w choice = 10. 130 Composition of Carcass Gain The composition of carcass gains for steers and heifers are presented in Tab1e 22. Adjusted to simiTar finaT carcass fat percentage, the 1arger framed steers deposited 16% more (P<<.005) carcass protein and 24% more (P<:.005) carcass fat per day than heifers. Differences in protein and fat energy gained dai1y wou1d be identica] to tissue gain differences since the constants 5.686 Mca1/kg protein and 9.367 Mca1/kg fat were used. Efficiency of Carcass Production Energetic efficiency dataare presented in Tab1e 23. Steers consumed 13% more (P <.005) metabo1izab1e energy dai1y than heifers. Totai carcass energy gained dai1y was 22% higher in steers y§_heifers when both were compared at 29.2% carcass fat (P <.005). At simiTar composition, steers were higher in energetic efficiency (14-32.!3 13.00%, P= .01). Dai1y crude protein intake was 13% greater (P <.005) for steers y§_heifers (Tab1e 24). However, efficiency of crude protein uti1ization for carcass protein production (%) did not differ (P >.10) by sex. Va1ues were 10.7% for steers and 10.2% for heifers. These va1ues may appear to be 10w, but inc1ude on1y the amount of protein deposited dai1y reiative to crude protein intake. Protein required for mainte- nance was not inc1uded in the efficiency ca1cu1ation. Data describing edib1e portion gained and metaboTizab1e energy (ME) required per kg edib1e portion produced are presented in Tab1e 25. .cwmumpe: x ecewmcmz x memc< u:2< mmquOLugu x eco2mcm: x mcmc< ”u2< mecowmcmz emuemme "2m meco2mcm2 emuemmec: "zmen .A2N.va comwchEee use :2 mFHuue Fpu we yum mmuecue cums ecu op empmsweu mew: uuuo .Ammv mcume exp cmezpmn mecmcmwmwe 82» 2o cesem ecuecupm ecu mcuws ecueem umumAu 131 2.2No.N u.mmo.m u.uow._ m.oum._ 826826: moo.v e.mu 2.uue.N m..u2.N N.22N.N o.Noo.N meaeum 2ee\_eee .ewem 2meeem eac m.ome m.2om m.m22 2.8mm meeewez 2ee\2682 moo.v m.u_ N.mum c.m2m N.omm N._22 meeeem .e2em 2meeee eweeoee 2.82N 2.2_N u.Nm2 m.uu~ meeewex moo.v 2.8 m.muN m.2uN o.o2N 2.m2N meeeem 2ee\m .ewem eac m.uu _.uu e.mw “.me meaeee: moo.v w.N 2.mm N._o_ 2.um w.Nw meeeem 2ee\m .ewem eveeoee m, m_ 22 m_ 828226: m2 m_ m_ __ meeeem mpeeeee co .oz xem mm :12 822 2m 1m: xem cape pm>w2 822p upppuu mecuem22cmwm a eeoweee emepwm cow: u emu mcmm2wx ecu mcempm me co2pwmoamo 2mgmcm ecu mcwuw mmuecuo co xmm me pomwmm .NN upnup 132 .oop x Fuuz .82uuc2 m: m _uez .e8c2um 2mc8c8 mmuecue 2—2u2 e .mL88pm _uwcp 582—82u28s 822 2223 e8cwsc8p8e mu .mx\_u82 mm.N eo 8zpu> mz cowpuc u co e8mume mmquocucu x eeew8c82 x mumc< uuz< mece28c82 e828828m .c28pmpe: x ecem8c8: x memc< ”2:< ”2m meeem8c82 e8288288c: ”2m: 2 .A2N.2Nv cem2cu2see 822 c2 8pupu8 __u we yum mmuecue cu8e 822 82 e8pmeneu 8L8: uuue 28:8282228 8228mc8c8 ecu cwum 2228c8 222u2 .Ammv mcu8s 832 c88328n 88c8c8wmme 822 we 28228 ecuecupm ecu mcu8E 8cu=em umu82u NTNP No.2 9.2 2.2 28:8: Po. N2.o m2.m_ mm.2_ m2.22 m2.22 82882m e2 .28c8282228 8228mc8cm Nm.N 2m.N mN.N em.2 8282282 moo.v 20.0 mo.m eo.m ow.N 22.N 8288pm 2ue\_u82 .cwum 2228cm 2o.ON 2e.w_ mm.22 Nm.2_ mc82282 moo.v 2m.o 2m.NN em.oN 88.22 mN.2_ mc88um 82ue\_u82 .82uuc2 22 m2 mp 22 m2 828228: m— m2 m2 FF 82882m mpuewcu we .82 X8m mm 22< 02< 2m 2m: x8m E822 28>8— 822p 8Fppuo 88cu8222cmwm a ucewpum 8mupwm 2822 u e82 8282282 ecu 82888m we 28:8282222 8228mc8cm ecu cwuw 2228cm mmueeuu .8xuucH 2228cm 8Fau~2Feeu88z co x8m we 288222 .mN 8_eu2 133 .2eo_ x 22 .82u2c2 c282ec2 8eece 2P2ue m 22 .e8c2ue c282ec2 mmuecue 222uev ce228=eec2 c282ec2 mmuecue Lew ce22u~2222e c282e22 8eece we 28:8282wwme .c282m—e2 x ecew8e8: x memc< ”:2< mm2u2eeugo x eLew8c8: x memc< HUI< meeew8c8: e828828m ”2m mecew8e82 e8288—8mc: ”Imam .Ammv mcu8E e32 c88328e 88c8c8wwwe 822 we Lecc8 ecuecu2m ecu mcu8e 8cueem 2mu82u mm.m mm.o_ 02.02 m_.op m28w28: 0N.A 00.0 00.0 20.29 00.22 20.02 mmepm 2 0.000000 000.0 220.0 222.0 000.0 mewwmI xwt\0x 000.v 000.0 000.0 220.0 000.0 002.0 mmeum xmxmucw :waOLQ wtaLo m— m— e_ m— mewva m2 m2 m_ 22 mc882m mFuE2cu we .ez xam um :12 812 1m 2m: xem c822 28>82 8222 8222ue 88cu82w2cewm e ce22u2 8mu22m 2222 u e82 828w282 ecu mc882m we ce2283eec2 c282ec2 mmuecuu e62 e022uN2m22= e282oe2 we 2eee2ewwwm eeu exe2e2 e282oea eezee 2.282 :6 xem we 2eewwu .2N e22u2 134 .202 .e8c2u0 c022202 8—e2e8 222ue m Fuez .82u2c2 22 222uev c02283eec2 c022202 8202e8 cow ce22uN2222: 2028c8 we 28c8282wwme .22N.0N0 cem2cuesee 822 :2 8222u8 __u we 2uw mmuecue cu8E 822 02 e82mene<8 .c2828202 x eLew8282 x memc< “22< mm2ureeu20 x ecew8c82 x mzmc< ”02< mecow8c82 e8288—8m ”2m mecew8282 e828828mc: “Imee .A0222 .xeu—m ecu x020 02N.0 m e822me28e c282ec2 mmuecue 222ue ”c022c02 8Fe2em .Ammv mcuus e32 c883280 88c8c8ww2e 822 we cecc8 eLuecu2m ecu mcuue 8cueem 2mu82u 00.00 2—.mm o_.Nm 2m.2m m28w28: 0N.A m_.m 20.2m mN.0m 22.22 No.2m m2882m eex\_u82 .2222 2mm.0 wmm.0 02m.0 20N.0 meuw282 e2ue\02 m00.v N20.0 202.0 N22.0 m0m.0 2mm.0 m2882m .e8c2ue c022ce2 8202em m2 m2 2_ m2 mc8w282 m2 m2 m_ 22 mc882m MFuE2cu we .ez X8m mm 22< 02< 2m 2m: xum 5822 28>82 8222 8222u0 8ecue2w2cm2m e c022u2 80u22m 2222 u e82 mc8w282 ecu mc882m we c02283eec2 c022ce2 8Fe2em eew ee228N22mee 2eeeem we 2eee2e2wwm eee eeeweu eeweeee 82e2em 2.2ee ee xem we 268228 .mN 82ee2 135 As noted for a11 measures of growth, dai1y edib1e portion gained was higher (P<:.005) for steers v§_heifers (0.378 v§_0.334 kg) when both were compared at simi1ar carcass fat. There were no differences in ME required per kg of edible portion produced. Va1ues were 52.18 and 55.10 Mca1 ME/kg edib1e portion for steers and heifers, respective1y. Economics Tota1 costs per 100 kg gain were ca1cu1ated from the observed performance of steers and heifers fed in this tria1. Nonfeed costs charged to sma11, average, and large frame catt1e are presented in Tab1e 26. Those costs directTy associated with initia1 and/or fina1 body weight (yardage, marketing, interest on feeder, and death Toss) were apportioned to the actua1 initia1 and fina1 weights of the four types of steers and heifers fed in this tria1. Feed and nonfeed costs for steers and heifers, based on three prices of corn, are presented in Tab1e 27. Averaged over a11 catt1e types, nonfeed costs per unit gain of steers were 8% greater than those of heifers. Feed and nonfeed costs per unit gain increased with increasing mature size in both sexes. At a corn price of $7.86/100 kg, tota1 costs as a percentage of the SH steers and heifers were 96, 95; 105, 101; and 110, 108 for the USH, AHC, and AHH steers and heifers, respective1y. The spread in costs between steers and heifers widened as the price of corn and soybean mea1 increased. 136 Tab1e 26. Nonfeed Costs for Sma11, Average, and Large Frame Catt1ea Charge Frame size Sma11 (181-381 kg) Average Large (227-476 kg) (272—572 kg) Yardage, $/day Veterinary, $/head Marketing, $/head Interest on feeder,b $/head/day Death Toss, $/headC 0.13 5.00 16.06 0.072 10.54 0.18 0.23 5.00 5.00 19.13 22.09 0.090 0.108 12.79 15.04 aSee B1ack and Fox (1977) for methods of aTlocating nonfeed costs. b 100 kg. Based on 10% interest/annum, and a purchase price of $143.30 per CBased on a 2% death rate, inc1udes 18 days of feed at $7.50/100 kg dry matter. 137 .we.om .epucemece .ceewwee mow.em .me cwEupw> www.mww .om< cwsupw> mmv.__ .pwum _ucecwE eeucp www.m .ecepmesww ”Amx oo_\mv pcupmcee meewce Lecpo .ww.mc .wo._N no moc.mm .mw.¢w ”m ”we.ww .mm.n n< ”Amx oow\mv Awe>wpeeemmc .wues cueezem ecu ccee we eewcee .mN mwnuh memo .m .N m—uwcp Lew emuce>u eepcmwezn .cwepmwe: x ecewecez x memc< uzz< mmwu—ecucu x ecewece: x memc< uuz< mecewecw: eepeewem “Im mecewece: empeewemc: ”Imeu uu_ me_ Now we_ wow _u _e _m.o mum mcawwaz mw eu_ me_ Ne_ oqw mm mm we co._ emu mcemem m_ =I< ccw em_ mm ov_ um cm um om.o mew mcawwmx m_ mc_ um_ cm wa mm em me me._ mam mcamem m_ eI< mc_ ¢m_ we cm_ we um cm vu.o New mcmwww: cw mu_ _m_ Nu omc Na em mm oe.c eem mummem mw Im New um_ mm mm_ um um um mc.e mom mcmwwaz m_ me_ um_ mm mm_ we Nu cm _a.o mam mcaaum __ 1m: e m < e m < scum ex ee_\w ex eaaw xwm .Ewcu eccu epmee eeewcez .wo< ece mxuo .ez uewppuu ecwum ox oo_\m ecwum mx oo_\w .mpmee wucew .mumee eee2 cewuum emuwwm cmwz u ee2 mcewwe: ecu mceepm cow mpmeu eeewcez ecu ewe2 .NN eweuw 138 Feeding Trials: High Silage vs High Grain Steers Data examining the effect of cattle type and energy level on the performance and carcass characteristics of steers fed high silage (HS) and high grain (HG) rations, are presented in this section. Results from trials conducted in each of 3 years were pooled as experimental designs were similar each year. However, steers fed HG in trial 1 received a 60% concentrate ration vs 80% in trials 2 and 2. Pooled least square means for HG cattle were calculated from the weighted average percentage concentrate (71%) for the 3 years. Initial Slaughter Cattle Dressing percentage and carcass composition data for the initial slaughter cattle have been previously presented (Table l9). Initial carcass weight and composition of the steers fed by Cricken- berger (1977) in trial 1 was estimated from the trial 2 initial slaughter steers. Intake, Gain, and Feed Efficiency Average daily gains, adjusted to the mean hot carcass weight within a cattle type, were 29% higher (P<:.005) in HG v§_HS steers (Table 28). The small framed USH steers gained at a slower rate than the remaining cattle types. Although differences were small, AHCsteers gained somewhat faster than SH (P .01) or AHH (P= .08) steers. On a kg steers. There were no differences (P> .l0) in relative gain between relative basis (g/w 5) gains were highest for SH and lowest for AHH USH and SH steers. '139 .Amo.uvcv cewueuceocw we>ew xocece x eexp ewupue u on eee eeumeu uoc muoewwe cwuzw .uceEepeezm ecu ccee wa mape emupwm ccoe Rem .mcewuuccheuee ceuaue ace cw mcecce cow umemeu o» .»Pe>wueeemec .ac.m ecu «.0 eemuececw ece: ccoe eceumwoe cow; ecu emupwm ccoe we mexuucwe .Aop.uvc au ucuewwwcmwm poc eexp ewupuu we ueewwe cwusv euuwceoceeu uec cemwcueeeu uep 2m zzc eI< cm cm: _e>ep ceec m> uz< m> :m m> 1m: epuuue xecec2 zecec2 eecxe epeeue a eecoewcueseu eexw mueewwe cwuz mceeum we zecewowww2 eeec ecu cwuw .exuucH co Fe>e2 zucec2 cowuum ecu eezw epuuuu we aeeww2 .mm e—cuw m 140 Dry matter intakes were similar among steers fed HS and HG (P> .10). Intake increased with increasing steer frame size and intakes by AHC and AHH steers were similar (P= .10). Cattle type differences in intake were removed, however, when expressed on a relative basis. A significant (P<:.05) cattle type by energy level interaction prevented analysis of the main effects of ration and type on feed/gain. There were no energy level x type interactions for USH, SH, and AHC steers. Specific type comparisons indicated no difference (P> .l0) in feed required per unit gain for SH y§_USH steers, while feed requirements for AHC steers were greater (P = .09) than those of SH steers. AHH steers required only l% more (P==.Ol) feed per unit gain than AHC steers when fed an HS ration. When fed an HG ration, however, requirements were l4% greater (P< .005). The relative efficiency of the Holstein crossbred steers was thus superior when fed HS v§_HG rations. Carcass Characteristics Carcass data were adjusted to similar carcass weight within a type primarily to examine the effect of energy level on carcass traits (Table 29). In general, energy level appeared to have a marked effect on carcass fatness while effects on carcass quality were minimal. Marbling scores were slightly higher in HG steers (11.97 vs ll.l9) although the difference was not significant (P> .10). Quality grades likewise favored (P= .03) HG steers (l0.02 y§_9.56 where 10 equals low choice). All measures of carcass fatness were higher (P<:.005) in 141 .ow u eewoce 3ow ”m u eeem cmwzw .an.+ppusm up— u ppuEm mop u_.~pusme .Aew..vc pu ucuewwwcowm eec eexu ewuuue we peewwe cwusv euuwceeceeu «cc comwcuesee ” me.m -.m wm.N mm.~ a: <2 <2 <2 eN.A mee.v Nw.e me.~ ~m.~ we.~ we.~ m: a .xex om.mw ~e.~m we.ew ev.mw a: meo.v meo.v o~.x mee.v em.x em.p we.mw m~.~w ew.ew oo.mw m: Nae .uecu ewe ewm me.— em.p em.— um.w e: m_. oN.A o~.x mee.v mee.v ee.o ww.— eo.p w~._ me.w m: so .uuw _ucceux2 mm.o_ w_.ow mo.e mm.e e: <2 <2 <2 om.x me. em.e Ne.e _w.e -.m wm.e m: weeucm xuwpueo up.mp Fm.~_ oe.ww we._w e: <2 <2 <2 eN.A mw. ew.e hm.N_ mm.ww m~.e_ eo.ep m: eecwwocuz emu cum ecu mum ex .ez mwuecue co: um um mm mp e: mm mm NN aw m: mceeem we .ez nlzz< .lmz< Ilrm eexu _e>ew 2m zz< uz< 1m 2m: _e>ew Eeuw m> uz< m> :m m> 2m: ewuuuu xmcec2 exacec2 gene“ epeeue emcomwcuesou eexw mueewwe cwuz mucmwez mmuecuu cu—wswm o» eeameee< ecez eoaw cwcuwz mceeum cecz muwuewceueucuco mmuucuu co we>em xmcecm cewuuc ecu eezw epuuuu we «eeww2 .mN e—ouw 142 steers fed HG. Carcass fat, external fat, internal fat (KPH), and yield grades were 15, 28, 15, and 13% greater in HG v§_HS steers, respectively. At similar carcass weight within type, there were no differences (P> .l0) in marbling or quality grades due to cattle type. Carcass data adjusted to the mean carcass fat of all steers (32.3%) are presented in Table 30. AHH and AHC steers tended to be superior in carcass marbling and quality grades. USH and SH steers were lower in carcass quality and did not differ (P >.10) from each other. Rib eye area was related to frame size although values were greater (P==.0l) for AHC y§_AHH steers and USH and SH steers did not differ significantly (P:>.10). At similar total carcass fat, external fat was not influenced by cattle type while internal fat of AHC steers was higher than either SH (P <.005) or AHH (P= .03) steers. Yield grades were numerically highest for AHH steers but were not signif— icantly different from AHC. SH steers had higher (P<<.005) yield grades than USH steers but did not differ (P2>.10) from AHC. Composition of Carcass Gain The chemical composition of carcass gain is presented in Table 31. Adjusted to similar final carcass fat, HG steers deposited 30% more protein and 25% more fat daily than HS steers. Differences in protein and fat energy gained were similar to the tissue gain data due to the constants used in calculating energy deposition. Daily carcass protein gained was similar among SH, AHC, and AHH steers. The small framed USH steers, however, deposited protein 143 x mzmc< .ow u eewoce cow we n eeem cmwzw .an+:.wEm «PP u _._.me "OF "I PFmEmw .Aow. v2 uu ucuewwwcmwm we: eexa ewuuue we peewwe cwusv euuwceoceeu uoc cemwcuesoo " No.2 w_.m Pw.~ ww.~ o: no. meo.v eN.A moo.v Np. Nw.e ew.~ we.m 22.2 Ne.~ m: u .222 om.ew mm.mw mm.ew mp.mw a: we. mee.v om.A moe.v 2e. ee.w em.ww wo._w mw.mw mm.~w m2 Nae .uecu ewe ewm mm.w em.w em.w v~.w e2 <2 <2 <2 ww. o~.x wo.o om._ w~.w em.w Nm.p m2 so .uuw Pucceux2 ee.e em.m mw.e we.m o2 eN.A moe.v oN.x mee.v mw. om.o w~.ow mm.o_ ee.m Pm.e m2 weeucm apwwuso ow.~w mm.w— pm.e em.ow w: 02.x moo.v om.x mee.v co. me.o ww.m— eo.~w mw.ew _o.ww m2 emcwwocuz em.~m u~._m ee.~m mm.~m 2 .puw wmuecue em em mm ow e2 mm mm mm ew m: mceeum we .ez .122< Im:< .Ilzm eexe we>ew 2m 22< u2< 2m 2m: we>ew Eeuw m> u2< e> 2m e> 2m: epuuuu wacec2 Amcec2 encomwcuesoe eezw o eecwu eweeue muoewwe cwuz uuuw meuecuo cuwwewm ea eeumeee< ecez mceeum cecz mowumwceuoucucu mmuecuu co _e>e2 xmcec2 cewuum ecu eexw e—uuuu we uoeww2 .om ewouw 144 mmwuwecucu x ecewecez x memc< ”o:< mecowece: eeueewem .wceeeweeem ecu ccoe 2ww mewe emuwwm ccoe 2mm ”22 mpceEeweeem mewe emuwwm ccoe “m: .cweumwoz x ecowece: x memc< uzz< "2m mecowece: eeuoewemc: ”Imee a .Awm.mmv mceepm wwu we puw mmuecue cues ecu op eepmeeeu ecez uuuo .A2mv ecuee ezp ceeZuee eececewwwe ecu we cecce ecuecuum ecu ecues ecueem pmue2u m.eww.u «.eww.m u.mmu.m o.uu_.m e2 wue\_uex em.x meo.v uoe.v mee.v mee.v _._u e.~ee.m e.e¢e.m u.w~w.u m.euu.~ m2 .cwue wecece euc e.ewu u.uwu u.wwe w.eum e: wue\_uex .cwue em.x om.x uoe.v ueo.v meo.v _.u_ u.euu N.uuu w.wmm u.u_u m2 zucece cweooca c.uum w.eee w.uum e.mmm e: wue\u eN.A mee.v mee.v meo.v mee.v w.e m.emm u.uuu N._em u.emm m: .cwue euc e.w_w u.e__ _.ew_ N.eew e: wue\u eu.x em.x mee.v mee.v moe.v e.N m._e m.~m w.~e u.mw m: .cwum cweuocc um we we aw e: mm mm mm ow m2 mceeem we .oz [.222 .1222 .lem ecwe _e>e_ 2m :22 e22 2m 2m: we>ec ceec m> oz< m> 2m m> 2m: ewapuu xmcec2 zucec2 eecwu e_uuue a mcemwcuesoe eexw mpeewwe cwuz mceeum we cowpwmoeea zmcec2 ecu cwuw mmuecuu co we>e2 emcec2 cowpum ecu eeaw ewppuu we peeww2 .wm e—euw 145 at approximately 80% of the rate noted in the three larger types. Rate of fat deposition was similar (P> .10) between AHC and AHH steers. SH steers gained less (P<:.005) fat daily than AHC steers (9%) but more (P<:.005) than USH steers (11%). Efficiency of Carcass Production Energetic efficiency data are presented in Table 32. HG steers consumed 15% more (P<:.005) metabolizable energy (ME) daily than HS steers. The larger framed AHC and AHH steers consumed similar amounts of ME (23.33 and 24.17 Mca1), while the other cattle type comparisons were significant (P<:.005). When compared at 32.2% carcass fat, HG steers deposited 26% more (P<:.005) carcass energy daily. As noted for ME intake, energy gains were similar (P> .10) between AHC and AHH steers while SH steers deposited 13% more daily carcass energy than USH steers and 8% less than AHC steers. When compared at similar carcass composition, carcass energy gained as a percentage energy consumed was greater (P<:.005) for steers fed HG rations (17.59 y§_15.97%). There was little variation in energetic efficiency among the British and British x Charolais steers (USH, SH, and AHC). However, percentage efficiency was 5% lower in AHH steers when compared to the average of the other types. Daily crude protein intake (Table 33) was higher (P<:.005) in HG v§_HS steers (0.974 v§_0.890 kg). Crude protein intake increased with increasing frame size although differences between AHC and AHH steers were not significant (P>-.10). Daily carcass protein gained, 146 mmwuwecucu x ecowece: x memc< .uceEeweeem ecu ccoe 2pm mzwe emuwww ccoe New ”2: mpceseweeem mewe emuwwm ccoe "m: "u:< mecowece: eepeewem .oow x wuez .exupcw 22 e _uez .eecwum xmcece mmuecue xwwuo e .cweumwoz x ecowece: x memc< ”22< “2m mecowece: eepeewemce "Imee o .A2N.va mceeum wwu wo puw mmuecue cues ecu op eepmeeeu ecez upue xecewewwwe ewpemcece ecu cwum amcece wwwue .A2mv mcuee exp ceezpee eececewwwe ecu we cecce ecuecuum ecu mcues ecueem umueeu we.e— mw.w— mw.ww Pm.ww 22 2 e.>ecewewwwe we. 02.x 02.x mo. moo.v mm.o mm.m_ _~.e_ ww.e_ m_.2_ m2 ewpemcec2 uu.w me.e _w.u ew.m e: wue\_uez eu.x moe.v moe.v mee.v moe.v ee.o Nu.u cm.m uN.u ue.u m: .cwum wucece ee.mm me.um mo.mu e¢.eu e2 wue\_uec mw. moo.v moo.v moo.v moe.v wm.o we.~m ew.wm me.om ee.ww m2 .exupcw 22 «N ew mm ow 22 mm mm mm ow m2 mceepm we .ez ..22< 1222 .luzm ecwe _e>e_ 2m :22 e22 2m 2m: we>ew ceuc m> uz< m> 2m m> 2m: ewpuuo xmcec2 camcec2 eeexp ewppuu mcomwcueeoe eexw mpeewwe cwuz mceepm we xecewewww2 ewuemcec2 ecu cwuw xmcec2 mmuecuu .exupcw xmcec2 eweuNwwoeuuez cw we>e2 amcec2 cewpum ecu eeaw ewupuu we weeww2 .Nm ewouw 147 cwepece mmuecuo wwwuev cowuezeoco cwepoce mmuecuo cow cowwuNwwwpe cwepoco eeoce we 2ocew www2 mmwuwocuco x ecowece: x momc< no:< mecowece: eepeewem .pceEe—ooom ecu ccoe 2ww mewe emuwwm ccoe 2mm .oe— x ex .ecupcw cwepoco eeece xwwue u ”2m mecowece: eepoewemc: ”w: mucesewooem mowo emuwwm ccoe m2 .eecwum e e .cwepmwo: x ecowece: x meec< uzz< ”Imce ”min .A2mv ecueE ozp cee3ueo eececewwwe ecu we cocce ecuecupm ecu ecues ecuoom pmueeu no. FF. mo. we. moo.v mm.o om.A _0. Po. moo.v moo.v mmo.w owo._ wem.o mow.o o: omo.o mum.o Nem.o eom.o mmw.o m: ow.o— me.—— mo.N_ oo.ww w: ww.m oe.ow mo.ww oo.ow m: em em mm m— 2: mm mm mm m_ m: ooaU e\ a 2222 xue\mx .exuucw cwepoce eeocu mceepm we .ez 122< |m_._< 12m e93 we>ew 2m 22< uz< 2m 2m: we>ew see; m> uz< m> 2m m> 2m: ewppuu emcec2 oxmcec2 eezp e—upuo mcomwcueeoe eezw mpoewwe cwuz o umceepm we cowoozeoce cwepocc mmuecuu cow cowpuNwwwp: cweuocc we xecewewww2 ecu exupcw cweuocc eeece xwwue co we>e2 xmcec2 cowuum ecu eoxw ewppuo wo peeww2 .mm ewouw 148 as a percentage of protein intake, was higher for the HG steers (11.32 y§_10.33%). There were no differences in efficiency of protein use between SH and AHC steers although the other cattle type comparisons were significant (P <.lO). Although SH, AHC, and AHH steers deposited similar quantities of carcass protein daily (Table 31), AHH steers appeared to utilize dietary protein less efficiently. When compared at similar carcass fat, steers fed HG deposited 30% more (P <.005) edible portion daily than those fed HS (Table 34). Gains were similar among SH, AHC, and AHH steers. Small framed USH steers, however, deposited edible portion at a rate approximately 82% of that observed in the other cattle types. Trends were predictably similar to results noted with carcass protein gain (Table 31). As indicated in Table 34, efficiency of ME use for production of edible portion (Mca1/kg) was not influenced by ration energy level (P >.10). USH steers required more (P= .07) ME per unit edib1e portion produced than SH steers. Holstein crossbred steers were highest in ME requirements but were not significantly different (P >.10) from AHC steers. Economics Total costs per 100 kg gain were calculated from the observed performance of steers fed HS and HG rations in these trials. Nonfeed costs were allocated to cattle of various frame size as previously described (Table 26). 149 .222 .eecwum cowpcee ewowee awwue u wuez .exupcw 22 Awwuev cewueeeece cowucee ewewee cow cewpuNwwwp: Amcece we zecewewww2e .ANm.NmV mceeum wwu we puw mmuecue cues ecu op eeumeeeec 2m :22 o2< 2m 2m: _e>e_ ceuc m> uz< m> 2m m> 2m: ewuuuu amcec2 o\acec2 eeexu ewppuu mcomwcueEee eeaw mpeewwe cwuz umceeum we cewpeeeocc cowuceo ewcwe2 cow cewwuNwwwpe xmcec2 we zecewewww2 ecu eecwuw cewpcee e—owe2 xwwuo co we>e2 Amcec2 cewwux ecu eoxw ewpuuo we peeww2 .em eweuw 150 Feed and nonfeed costs for cattle fed in this comparison are presented in Table 35 based on three possible prices of corn. Averaged over all cattle types, nonfeed costs were 21% greater for steers fed HS v§_HG rations. Feed and nonfeed costs per unit gain increased with increasing mature size for steers fed both rations. On a total cost per unit gain basis, the HS and HG rations were essentially equal for the British and British x Charolais steers (USH, SH, AHC) at a corn price of $21.61/100 kg. For AHH steers, however, this point would be reached at a corn price slightly greater than $7.86/100 kg. 151 .we.em .epucomoce .coowwee momem .mo cwEupw> ”22.222 .om< cwsupw> ”22.22 .pwum _ucecws eeucp ”22.2 .ecoumeaww "Aux oo_\mv pcupmcoe meewco cecpo .m—.ee .we.wm no woe.mm .mw.2_ "m mw2.w— .ow.w H< ”Aux oo_\mv awe>wpoeomec .wuee cueozom ecu ccoo we eewcce .mm ewouh meme .m .N .w mwuwcp cow emuce>u eepcmweze .ucesewoeem ecu ccoe 222 mewo eeuwwm ccoe 222 no: mpcesewooem mewe emuwwm ccoo umzo .cwepmwoz x ecowecez x memc< ”22< mmwuwocuco x ecowece: x momc< ”222 mecowecez eepeewem “2m mecowecez eewoewemce ”Imeu mom umc mow eec uwc me 02 mm._ emu e2 22 me_ c2c uow P2P oec um e2 _e._ New m2 mm :22 ee_ 02w mm 22_ New em cu Nu.c emu e2 22 2e, u2w New 02c um um m2 2o._ New m2 mm e22 ccc umc we m2_ we 2m 2m cu._ emu e: um ucw umw cm mmc um em _2 22.0 emu m: we 2m mcw omw eu N2, we mm mm 2_._ emu 2: ac ucc mmc um mew um um o2 eu.o cum m: ac 2m: o m 2 o u 2 cwue 22 eewcu 22 eeew _e>e_ mceeum ecwu “moo eeewcoz .2Q< eco exuo xmcec2 .ez uewupuu e n ecwum 22 ee_\c eccue ac eo_\w .mpmou :38. .wumou ewe... mcowpum cwucw cow: ecu eeuwwm cow: eew mceeum cow mpmou eeewcoz ecu eeew .mm ewouw DISCUSSION Cow-Calf Trials Energy Requirements Cow-calf trials were not designed to define a particular energy requirement for specific types of cows. Rather the objective was to observe the adequacy of existing feeding standards (NRC, 1970 in trial 1; NRC, 1976 in trial 2) for various types of cows subjected to harsh climatic conditions. Reliable assessment of cow body condition was of considerable concern in evaluating the energy levels fed. Klosterman et_al, (1968b) has pointed out the inaccuracies of using weight as an indicator of cow body condition. He suggested weight to height (at the hooks) ratio as an alternative. In the present study condition was assessed from fat- ness over the 12th rib as estimated ultrasonically on a monthly basis. In the feedlot phase of the research, a simple correlation of 0.72 was found between this method of estimation and actual fat thickness in 176 steers of the four genetic types (USH, SH, AHC, and AHH). Ultra— sonic estimates of fat thickness were obtained immediately preceding slaughter. In trial 2, heighth of cows at the hooks was measured at the beginning and end of the trial and weight/height ratios were calculated as a comparative method of assessing body condition. Simple 152 153 correlations between ultrasonic fat thickness and weight/height ratios were 0.44 and 0.63 for initial and final values, respectively. Trial 2 cows averaged 0.65 cm fat initially and 0.42 cm at the end of the trial. Thus, the two methods of estimating body condition appear to be more closely related for the thinner cows. Cow-calf trials were conducted from December 16, 1975 to September 9, 1976 (trial 1), and from November 23, 1976 to September 19, 1977 (trial 2). Three levels of TDN intake may be compared in the two cow-calf trials: (1) NRC (1970) with a 25% increase in amounts of lactation ration; (2) NRC (1976) throughout the trial, and (3) NRC (1976) plus 25% throughout the trial (trial 1). Pooled across cattle types, TDN intake was 5.91, 4.75, and 6.07 kg and percentage of initial body fat recovered at the end of the trials were 100, 51, and 83%, for systems 1, 2, and 3, respectively. Intakes were similar among cows fed system 1 and 3 due in part to differences in trial length (more days on maintenance rations for system 3 cows). The greater weight and fat recovery of system 1 v§_3 cows is likely associated with the more severe environmental conditions encountered for the latter (Table A.5). Hironaka and Peters (1969) found a close relationship between cow weight changes and average temperature and wind speed. Christopherson (1976) found significant effects of cold exposure on ration digestibility. Shorter ruminal retention times and lower fiber digestibility have also been reported at low y§_high temperatures (Warren _t__l,, 1974). Thus, TDN intake may be overestimated during the winter months when calculated from average values (NRC, 1976). 154 Some evidence for a differential response to the conditions imposed were noted. Trial 1 Holstein crossbred cows were the only cattle type not regaining their initial body weight and Trial 2 Holstein crosses tended to lose more weight on both rations although differences were not significant (P> .10). However, Kropp et_al, (1973) found no treatment x breed interactions in preweaning productivity for Hereford, Hereford x Holstein, and Holstein cows fed three levels of winter supplement. While larger cows have been assumed more ”cold resistant” than small cows (Kleiber, 1961; Blaxter, 1962; Christopherson, 1976), general trends indicated the opposite in the present studies. However, the size relationship is likely confounded with breed. Webster and Young (1970) found inferior thermal insulation values for Holstein y§_beef breeds. Unfortunately, reproductive performance could only be evaluated for trial 1 cows (all cows fed the same energy level) and thus numbers were rather limited for definitive conclusions. 0f 36 cows included in the comparison, 42% were cycling when inseminated and 22% became pregnant. The lactation ration was increased 25% at 52 days before breeding but energy intakes were apparently too low for acceptable reproductive performance. Jordan §t_al, (1977) compared Shorthorn cows fed hay or grass silage at 50, 75, and 100% of ag_libitum intake during the last two-thirds of pregnancy. Pregnancy rates for cows \wintered outside (northern Ontario) were 58.3, 80.6, and 88.9% for the three levels of intake, respectively. Similarly, Davis gt_al, (1977) found that energy and not protein limited reproductive performance of Hereford cows. 155 Preweaning Calf Performance Results of trial 2 indicated little effect of precalving energy intake on birth weights of calves. In all trials birth weights were lower for the small framed USH calves while differences among the remaining types were small. Adjusted weaning weights increased with increasing mature weight of dam, regardless of nutritional regime. Similar results were reported by Carpenter et_al, (1972b), Brinks gt_al, (1962), and Klosterman et_al, (1968a). Preweaning calf average daily gain favored the crossbred calves (AHC and AHH). Klosterman gt _1, (1968a) found small but consistent evidence of hybrid vigor for weaning weight and daily gain in a com- parison of Hereford, Charolais, and Hereford x Charolais crossbred calves. In trial 2, calf preweaning average daily gain (ADG) was 15% faster in calves from high v§_low energy dams. Higher levels of milk production may be inferred for dams fed high energy although direct estimates were not obtained. AHH calves were consistently higher in preweaning ADG on all nutritional regimes. Similar increases were noted in comparisons of calves of 0, 25, and 50% Holstein breeding (Holloway §t_al,, l975a; Wyatt et al., 1977c). Wyatt gt_al, (1977a) in a cross-nursing experiment, found increased weaning weights of approximately 20% for Angus x Hereford and Charolais x Holstein calves raised on Holstein .vs Hereford dams. Both types of calves consumed similar amounts of milk when nursed by Holstein cows. 156 Efficiency of Production Discussion of efficiency data will focus on the estimates made for a full productive year. In three of the four cattle types (SH, AHC, AHH) the total feed TDN required to produce a unit of calf weaning weight increased with increasing TDN consumption. Considering efficiency of feed conversion only, this seems to indicate the lowest energy level fed (NRC, 1976) was the most desirable. However, as discussed subsequently, other factors must be evaluated in selection of a feeding system. Pooled over the three nutritional regimes used, total kg of TDN required per kg calf weaning weight were 10.27, 10.05, 9.12, and 9.02, for USH, SH, AHC, and AHH cows, respectively. Thus, the largest variation in values was a 14% greater requirement for USH v§_AHH cows. The efficiency va1ues observed may be compared with similar data reported by Klosterman and Parker (1976). They found efficiency of feed conversion values of 10.1, 8.6, 10.0, and 9.2 for Charolais and Hereford sired calves from Hereford, Hereford x Angus, Hereford x Charolais, and Charolais dams, respectively. Cows and calves in that study, however, had access to shelter. While data could not be subjected to statistical analysis, in two of the three nutritional regimes compared, AHH cattle were superior in conversion of TDN to calf weaning weight. Increased milk Yields and efficiency of feed use for milk production as percentage Holstein breeding increased were noted in comparisons of Hereford, Hereford x Holstein, and Holstein cows as 2—year-olds (Kropp gt_al,, 157 1973); 3-year-olds (Holloway et_al,, l975a); and 4- and 5-year-olds (Wyatt et_al,, 1977c). Results of the cow-calf trials indicate that current NRC (1976) requirements for energy are at least 25% too low when cows are main— tained without shelter in harsh climatic conditions. Jordon gt_al, (l977) concluded that Shorthorn cows confined outside required year- round ag_libitum feeding of roughage under severe environmental conditions. While total TDN requirements per unit weaning weight averaged 15% higher in trial 2 cows fed NRC + 25% y§_NRC, the ability of the cows to rebreed must be considered. Further, price differentials for calves of various weights and the cost of feed in relation to the sale price of the calf would have to be evaluated in determining the energy level desirable for each type. It must be stressed that cows were exposed to extremely severe environmental conditions. Therefore, the results of these experiments are only applicable to cows maintained in a similar manner. However, the energy requirements recommended by NRC (1976) were uniformly low across all cattle types when AHH cows were fed at the "superior milking ability” level. Thus, published requirements based on cow weight and expected milking ability are likely valid under unstressed conditions. 158 Metabolism Studies Nitrogen Utilization The high silage (HS) and 80% high grain (HG) rations fed in the metabolism trials were supplemented with soybean meal to 13.45 and 14.45% crude protein according to the requirements outlined by Fox and Black (1975). Therefore, evaluation of protein levels pgr_§§_ was of little interest since animals were likely supplemented at or above their requirements. Holter and Kabuga (1974) found similar nitrogen utilization of high silage rations with increasing levels of crude protein above 10%. While fecal nitrogen excretion is typically more related to nitrogen intake than source of nitrogen (Moran and Vercoe, 1972) the higher nitrogen intake of HG y§_HS steers was associated with non- significant (P> .10) differences in quantity of fecal nitrogen excreted. Nitrogen digestibilities of 58.5% for HS and 66.8% for 80% concentrate (HG) rations compare with values of 66.2 and 68.9 (60% concentrate) in corn-corn silage rations fed by Crickenberger (1977). In that study, both rations were supplemented to 12.8% crude protein. Nitrogen retention (g/day) was 50% higher in steers fed HG '1; HS rations. Although only speculations can be made, a greater quantity of feed protein and/or microbial protein likely passed to the lower digestive tract of steers fed HG. However, Bergen et al. (1974) has questioned the value of corn bypass protein (Zein). 159 Crickenberger (1977) reported that non-ammonia nitrogen passage to the abomasum was 57.6 and 78.9 g/day on HS and HG rations, respec- tively. Total nitrogen intake was similar for steers fed both rations. In the present study, steers fed HS and HG rations consumed 14.84 and 18.72 Mca1 of metabolizable energy (ME) daily as determined by the energy balance data. Broster (1973) noted an increase in nitrogen retention as ME intake increased. Nitrogen retention as a percentage of absorbed nitrogen was 19% higher for the HG v§_HS ration although the difference was not significant (P'>.10). Nitrogen retention as a percentage of nitrogen intake was significantly higher in the ”3.22 HS ration (32.6 v§_24.2%). A "net protein" system for predicting protein requirements and feed protein values for growing and finishing catt1e has been proposed by Fox gt_al, (1977). In that system, conversion factors (nitrogen retained as a percentage of nitrogen intake) are multiplied times feed crude protein values to obtain "net protein" values for various feeds. Preliminary conversion values of 0.30, 0.20, and 0.35 were presented by Fox et_al, (1977) for high moisture corn, corn silage, and soybean meal, respective1y. Calculated net protein conversion factors for the mixed rations fed in this trial would be 0.22 for the HS ration (y§_0.242 observed) and 0.28 for the HG ration (v§_0.326 observed). Overall, variation in nitrogen utilization between steers fed HS and HG rations were more pronounced in the present study than the previously cited work of Crickenberger (1977). However, catt1e fed 160 HS and HG in the latter study consumed similar amounts of dry matter and nitrogen while these values were markedly higher in HG steers fed in the present studies. Several trends relative to cattle type were observed in nitrogen utilization. Intake and excretion amounts were influenced by cattle type (increasing with cattle size) while there were no dif— ferences (P> .10) in any measure of nitrogen retention. In comparison of steers of similar frame size (AHC and AHH) there were consistent but nonsignificant trends for a greater fecal and urinary nitrogen excretion in AHH steers. Simi1ar patterns in Holsteins y§_Angus steers have been reported (Crickenberger, 1977; Ayala, 1974). AHH steers in the present study were approximately one-third Holstein breeding. Net protein values were not influenced by cattle type in the present study. However, all steers were young growing animals of similar physiological maturity. Net protein values need to be deter- mined with animals fed different protein levels at different stages of maturity. Energy Utilization The greater digestibility of the HG v§_HS ration was evident from a lower feca1 energy excretion with higher dry matter (P= .04) and energy intakes (P> .10). Urine energy excretion was similar among steers fed the two rations and was expected from the nonsignificant difference in urinary nitrogen excretion. Energy retention (intake- feed-urine-gas energy), and thus metabolizable energy values, of the HG ration were predictably higher than the HS ration. Pooled across 161 catt1e types, ME values were 2.58 and 2.96 Mca1 ME/kg ration dry matter. Calculated from average published values (NRC, 1976) for the feedstuffs in the rations, the ME values were 2.56 and 3.01 Mca1/kg for the HS and HG ration, respectively. In this trial, errors in determining ME intake of the feedlot catt1e would have been minimal had "book values" been used. Catt1e type differences in intake, excretion, and retention of energy were largely related to animal size. 0f the specific type comparisons conducted, largest differences were noted between USH and SH steers. ME values were not influenced by cattle type. The maximum variation in energy digestion coefficient was 0.6 units for the HS and 4.2 units for the HG ration. Most workers have found little difference in digestive powers among conventional cattle of various types (Reid, 1962; Washburn et_al,, 1948). However, some workers have found superior ability to digest roughages in cattle 1960; French, 1940; Phi11ips §£_gl,, 1960). Feeding Trials: Steers vs Heifers Intake, Gain, and Feed Efficiency Adjusted to similar carcass composition, steers gained 19% faster than heifers when both were fed a high si1age ration. This difference in rate of gain is similar to many values reported in the literature, a1though heifers fed in the present study were those remaining after herd rep1acements had been selected. 162 Establishing the expected spread in performance between steers and heifers is important in economic planning. The following studies (Table 36) selected from the literature compared steers and heifers at similar final composition. Various straightbred and crossbred compar- isons are included as well as several energy levels. Table 36. Comparative Gains of Heifers and Steers a b Steer ADG/ Study Breed Energy level Heifer ADG Newland (1976) A Low 1.18 A High 1.18 Bose §t_gl, (1970) H Pooled High & Low 1.10 Bradley §t_al, (1966) H, HX Low 1.17 H, HX High 1.18 Klosterman gt_gl, (1968a) H, C, H) .10) with heifers requiring only 2% more feed/gain. However, the adjusted data must be considered as an estimate only since the adjustment equations of Fox and Black (1977) have not been thoroughly tested over a wide range of cattle types, sexes, energy levels, etc. 164 Bose gt_al. (1970) found a 10% greater feed/gain value for heifers vs steers when both were compared at similar final composition. An 11% greater requirement for heifers v§_steers was reported by Bradley gt_al. (1966). Conversely, Ritchie gt_al, (1977) noted more efficient gains in heifers when the entire calf crop (steers and heifers) was compared at similar finish. An energy level x sex interaction was proposed by Kosterman and Parker (1976) who found the net energy value of corn silage was 16% greater when fed to heifers lg steers. Heifer ”quality” in the present study appeared to differ in the two trials conducted. In the first steer-heifer tria1, heifers required an estimated 8% more feed/gain than steers when compared at similar finish. However, the combined two—year comparison data pre— viously discussed indicated no significant differences. Each year the heifers fed were those rejected as herd replacements. Factors causing a poor weaning weight (and culling from the herd) may include sickness, injury, or nutritional stunting as well as genetic inferiority. Carcass Characteristics Adjusted to similar carcass fat (29.2%) there were no differ- ences (P> .10) in quality grade or rib-eye area. Steers, however, had more external fat and higher numerical yield grades. Several workers have observed a requirement for greater fatness in heifers to achieve the same quality grade of steers (Klosterman and Parker, 1976; Cooper t a1., 1972; Ritchie §t_al,, 1977). This was not apparent in the steers and heifers compared in the present study. 165 Composition and Efficiency of Carcass Gain Adjusted to similar total carcass fat, the larger framed steers deposited 16% more carcass protein and 24% more carcass fat per day than the heifers. Based on the live weight gain data, however, these differences in rate would likely be minimized if calculated on a relative basis. Although not an indication of the total amounts of protein and fat gained, heifers deposited 29.3% of total (protein + fat) daily gain as protein v§_27.9% for steers. Tota1 carcass energy deposited daily was 22% higher for steers which also consumed 13% more ME. The higher caloric efficiency of fat deposition was evidenced by the higher unadjusted energetic efficiency values for heifers y§_steers (30.1 v§_28.2% carcass fat). However, when adjusted to equal carcass fat (29.2%), daily carcass energy gained as a percentage of ME intake was 14.32 v§_l3.00% for steers and heifers, respectively. Thus, when taken to similar final composition, the heifers apparently uti1ized ingested energy less efficiently for gain than steers. This trend existed in the adjusted feed/gain data although differences were not significant. Despite a somewhat higher proportion of tissue gain as protein in heifers v§_steers, feed/gain values were 2% higher for heifers when feed conversion was adjusted to constant carcass fat. Similar trends (but greater inefficiencies for heifers .g§_steers) were reported by Hedrick gt_gl, (1969). While intake of ration crude protein differed by 13% (steers > heifers) the efficiency of prtein use for carcass protein production 166 was similar among steers and heifers (P> .10). Values of 10.7% for steers and 10.2% for heifers were considerably below the 24.2% of nitrogen intake retained in the bodies of steers fed a similar high silage ration in the metabolism studies. However, in the case of the nitrogen balance trials, retention of protein in noncarcass body tissues are accounted for. Further, steers fed in balance trials were at an early stage of growth when protein requirements were high. The lower efficiency measured over the entire tria1 could indicate excess dietary protein at heavier weights. Amounts of edible portion produced dai1y predictably followed the trends noted for carcass protein gain (13% greater for steers v§_ heifers). ME required per unit edib1e portion produced was similar (P> .10) between steers and heifers. Since: (1) days on feed were similar for steers and heifers; (2) little evidence exists for variation in maintenance requirement due to sex (Blaxter, 1962) and (3) edib1e portion, by definition, contains a constant proportion of fat, little difference in efficiency of production was expected. Suess gt_al, (1966) found no difference in percentage retail cuts between Angus crossbred steer and heifer calves. Three slaughter weights were employed and increasing live-weight from 386 to 455 kg increased retail yield of steers and heifers but there were no sig— nificant changes in carcass grade, marbling, or palatability. 167 Economics The economic projections were based on an equal purchase price for steers and heifers. In most areas heifers would sell at a discount and thus, the interest charge on the heifers may be overstated. The economic advantage in nonfeed costs per unit gain for heifers vs steers were more than offset by increased feed costs at all prices of corn greater than $7.86/100 kg. This resulted from the less efficient liveweight gains of the heifers. The cost dif- ferential between steers and heifers widened as the price of feed increased. This was caused by the higher feed/gain requirements of the heifers and became an increasing economic force as the price of grain increased. Feeding_Trials: High Si1age vs High Grain Steers Intake, Gain, and Feed Efficiency Daily gain data were adjusted to the mean hot carcass weight (HCW) within a cattle type. HCW was found to be a highly significant (P<:.01) continuous covariate in the equation estimating least square means for daily gain, while carcass fat was of less importance. This was expected when it was noted from plots of HCW v§_carcass fat (within pens) that considerable frame size variation occurred (i.e., a relatively "flat" relationship), and daily gains are closely related to frame size (Fox and Black, 1977). 168 Average daily gains were 29% greater for cattle fed 71% concentrate high grain (HG) v§_9% concentrate high si1age (HS) rations. The pooled results of cattle fed 13 and 15% crude protein rations by Hatfield gt_gl, (1971) revealed a 33% greater gain for cattle fed a 67% high moisture corn ration y§_those fed high silage. In that study, results were variable when considerably lower ration crude protein levels were fed. However, these relationships are not of concern in comparisons with the present studies since all cattle were adequately supplemented according to the system of Fox et_al, (1977). First year results of USH, SH, AHC, and AHH steers fed HS and HG rations confirmed the adequacy of the protein system used throughout the 3 year study. Fox (1977) reported that, in general, daily gain increases as the energy density of the ration increases to a level of approximately 70 to 80% corn in corn-corn silage rations. These observations were confirmed by the work of Jesse §t_§l, (l976b) and Prior gt_al, (1977). Assuming a corn grain content in corn silage of 50%, cattle in the present studies received a HG ration which averaged 86% concentrate (corn grain + soybean mea1-mineral-vitamin mix). Dai1y gains increased with increasing frame size for the Hereford and Angus x Hereford x Charolais steers (USH, SH, AHC). A linear relationship between frame size and rate of gain is implied in the performance simulation model of Fox and Black (1977) with rela- tionships based on an extensive review of the literature. Holstein crossbred (AHH) steers gained at less than expected rates based on their frame size. Similar results were reported by 169 Crickenberger (1977) for straightbred Holstein y§_Angus steers. However, Wyatt gt_gl, (l977b) and Dean gt_gl, (1976) observed increasing rates of gain as percentage Holstein breeding increased from 0 to 25 to 50%. Increased rates of gain for AHH y§_SH steers are consistent with the results of Kidwell and McCormick (1956). As previously explained in the steer yg; heifer comparison, daily gains were expressed per unit of metabolic body weight to remove differences due to frame size as nearly as possible. Expressed on this basis, daily gains tended to favor the smaller USH and SH steers. A similar trend was noted by Ferrell et_gl, (1978) who compared a wide variety of beef and dairy breeds. The higher relative ADG of SH g; AHC steers was not supported in the review of literature where such differences have been small. Daily dry matter intake did not differ for steers fed the HS and HG rations. Cattle type differences were predictably associated with cattle size. Intakes of AHH steers (approximately one-third Holstein breeding) were 3.5% greater than AHC steers. Wyatt gt_gl, (1977b) found a 4% increased intake with steers of 25% Holstein breeding v§_British x Charolais or Angus crossbreds. Intakes of steers with 50% Holstein breeding were 11% greater than the other crossbreds. Similar trends were reported by Dean gt_gl, (1976). The performance simulation model of Fox and Black (1977) predicts similar relative intakes (g/Wkgs) for British and British x Exotic: crossbred cattle. However, relative intakes of straightbred Holstein and British x Holstein crossbreds are predicted to be 17 170 and 9% greater, respectively, than beef breeds. In general agreement with the simulation model (Fox and Black, 1977), Ayala (1974) found increased relative intake in straightbred Holstein y§_Angus steers. In the present study, intake tended to be higher for AHH steers but differences were small. Thus, results tend to confirm the Fox and Black (1977) predictions for beef breeds while the intakes of the Holstein crossbred (AHH) steers were less than predicted. The main effects of energy level and cattle type on feed/gain could not be assessed statistically since a cattle type x energy level interaction was noted. However, a comparison of the least square means indicated a 34% increase in feed/gain requirements for HS y§_HG steers. Hatfield gt 11. (1971) noted a 54% increase in feed/gain for steers fed HS y§_HG (67% corn) rations. Standard analysis indicated no difference in feed/gain between SH and USH steers while some evidence existed for larger feed requirements in AHC y§_SH steers (P= .09). The AHC y§_AHH type com- parison was conducted independently for the HS and HG rations due to the aforementioned interaction. Although both comparisons differed (P= .01, P<:.005), Holstein feed/gain requirements as a percentage of the mean of the other types were 103 and 117% for the HS and HG ration, respectively. Thus, AHH steers performed relatively better on HS y§_HG rations. Significant catt1e type x energy level interactions were reported by Larson et_al, (1966) and Bond et_al, (1972). However, in those studies, Holsteins appeared to be more adapted to high grain rations. Nonsignificant cattle type x ration interactions were found 171 by Ferrell t l. (1978), Klosterman gt_gl. (1968b), Freeman (1969), and Harwin gt_al. (1966). Feed/gain was found to be independent of frame size for British and British x Exotic crossbred cattle by Fox and Black (1977), Brown t al. (1973, 1974), Smith et a1. (1977), Klosterman gt_gl, (1968a), Brungardt (1972) and Prior EE._l; (1977), when cattle were fed to similar final composition. However, in the present tria1, there was a tendency for smaller framed cattle to be more efficient, a trend reported by Ferrell §t_al, (1978). The lower relative daily gain of AHH steers, coupled with equal or greater relative intake suggests a poorer efficiency of Holstein crossbred cattle and this was apparent in the feed/gain data. Dean et_al, (1976) and Wyatt gt_al, (l977b) found significant increases in feed required per unit gain as percentage Holstein breeding increased from 0 to 25 to 50%. The decreased efficiency of AHH steers may be attributed to a higher maintenance requirement, a poorer utili- zation of energy intake above maintenance for productive purposes, or a combination of the two. Higher maintenance requirements for Holstein cattle relative to beef breeds has been reported by Hashizume et_al, (1963), Garrett (1971), and Ayala (1974). In addition, Garrett (1971) found increased feed requirements above maintenance per unit gain in Holstein y§_Hereford steers. 172 Carcass Characteristics At simi1ar carcass weights within a cattle type, HG cattle were higher in carcass fat and external fat while there were no significant effects on carcass quality. Workers finding little effect of nutritional regime on carcass quality inc1ude Jesse et_gl, (l976a), Reid gt_al, (1968), Epley gt_gl, (1971), and Crickenberger (1977). Catt1e types effects and patterns of fat distribution are of primary interest in the carcass data adjusted to the similar carcass fat of a11 steers in the comparison (32.3%). At similar carcass fat, AHH steers tended to have higher marbling scores a1though differences between AHC and AHH steers were not significant for marbling score or quality grade. Several earlier studies (Garrett, 1971; Cole et_gl,, 1964) have reported inferior carcass quality for cattle of Holstein breeding. In many comparisons, however, Holstein steers were slaughtered after the same number of days on feed or at similar weights as their British breed counterparts. Therefore, they were typically leaner and had not yet deposited sufficient intramuscular fat (younger physiological age). Also Holsteins have benefited from the 1976 revision of the beef grading standards, which abolished con- formation as a factor in determining qua1ity grade. In the present study, and those reported by Wyatt §t_gl, (l977b) and Dean gt_gl, (1976), Holstein crossbred steers compared very favorably to beef breeds in marbling score when compared at similar final composition. 173 Internal fat (KPH), as a proportion of total fat, has been higher for Holstein v§_beef breeds in several studies (Dikeman gt_gl,, 1977; Charles and Johnson, l976a; Crickenberger, 1977). This was not observed for AHH steers in the present study. Highest levels of internal fat (when compared at similar carcass fat) were found in AHC steers. However due to slightly higher external fat and smaller rib-eye area in AHH steers, yield grades were not different (P>-.10). At similar carcass fat, differences in fat distribution in HS v§_HG cattle were rather small. External fat, internal fat, and yield grades were not affected by energy level. Marbling scores, however, were 12.13 and 11.11 for HS and HG steers, respectively (P==.06). Lawrie and Kirton (1956) reported that intramuscular fat deposition was more age than plane of nutrition dependent. HS steers in the present study were on feed an average 55 days longer than steers fed HG. Composition and Efficiency of Gain Significant effects of ration energy level on the amounts of protein and fat tissue gained daily were noted. The lower daily- protein deposition of HS steers likely resulted from a lower intake of metabolizable energy. Thus, HS steers were unable to reach their maximum rate of protein deposition as outlined by Bergen (1974). Since cattle were compared at similar final body composition, and HG steers were killed after a few number of days on feed, the higher dai1y fat deposition of HG cattle was expected. 174 Daily rates of carcass protein deposition were similar among SH, AHC, and AHH steers and lowest for USH steers. Eversole (1978) presented muscle nucleic acid data for 6 steers per cattle type, selected at random (3 per energy level) from the cattle fed in this study. The concentrations (mg/g wet tissue) and total amounts (mg) of RNA in the semitendinosis muscle were 0.79, 1316; 0.93, 1783; 0.95, 2243; and 0.88, 1810 for USH, SH, AHC, and AHH steers, respec- tively. Thus, the smaller muscle mass of USH steers is apparent as well as less protein synthetic machinery per unit muscle weight. The total carcass energy gained was related to the amounts of protein and fat tissue deposited as previously discussed. Compared at similar final carcass composition, the percentage of ME intake recovered as carcass energy was 15.97 and 17.58% for the HS and HG rations, respectively. The increased energetic efficiency of steers fed HG gs HS rations was likely associated with a shorter length of time on feed. A smaller proportion of the total ME intake of HG steers would be used for maintenance functions, with more ration energy available for tissue gain. While Kleiber (1936) indicated no relationship between cattle size and energetic efficiency, breed differences exist. AHH steers were 5% less efficient than AHC steers in conversion of ration calories to carcass calories. Garrett (1971) reported increased maintenance requirements of 5 and 12% in two studies comparing Holstein and Hereford steers. Further, in that study, tissue gains per kg of feed above maintenance were 24 g of protein and 115 g of fat for 175 Hereford steers and 24 g of protein and 86 g of fat for Holstein steers. Thus, Holstein steers appear to expend more energy for maintenance and are less efficient in utilization of energy available for productive purposes. The efficiency of utilization of ration crude protein for carcass protein production was higher for HG vg HS rations, a result consistent with the nitrogen balance trials. Efficiency of protein utilization was poorest for AHH steers. Crickenberger (1977) quoted the data of Ayala (1974), indicating the increased energy requirements per unit metabolic weight for Holsteins, and Smuts (1935), showing the maintenance requirement of protein was related to basal metabolism. He thus concluded that given a positive relationship between the two physiological processes, Holsteins might be expected to have a higher maintenance protein requirement than beef breeds. However, this may not be a valid explanation if the higher ME requirements of Holsteins are simply due to a higher heat loss. Efficiency of ME use for production of edible portion was not influenced by ration energy level. AHH steers tended to have the highest requirements, and this was likely related to a greater pro- portion of ME intake used for maintenance. Similar observations for Holsteins relative to beef breeds were made by Larson gt_al. (1966), Garrett (1971), and Burroughs et_al, (1969). USH steers required more (P= .07) ME per kg edible portion produced than SH steers. As previously indicated, edible portion is, By definition, closely related to carcass protein production. The 176 lower concentration of RNA per g of muscle tissue in USH steers, coupled with similar relative intakes, may indicate an inability to more efficiently use the ingested ME for lean tissue production. However, USH steers were only 3% less efficient than AHC steers in conversion of ME to edible portion. Economics At a given price of corn, total costs per unit gain were higher as the frame size of the steers increased. Crickenberger and Black (1976) found a slight economic advantage for smaller framed cattle in the feedlot. They observed that increases in daily gain of larger framed cattle were not large enough to pay for the increase in nonfeed costs resulting from additional interest on the feeder and greater use of transportation and facilities. In their work, however, the variation in total costs among cattle of various frame size was smaller than noted ‘in the present trial. This is due to the decreased feed/gain require- ments with decreasing frame size in the present study, while in the work of Crickenberger and Black (1976), feed/gain was held constant. Averaged over the USH, SH, and AHC steers, daily gain and feed/ gain values were 29% higher and 28% lower, respectively, for steers fed HG y§_HS. Given these observed differences, the price of corn would be $21.61/100 kg before the HS ration would be competitive. However, given the relatively poor performance of AHH steers fed HG, the corn price required to make the HS ration competitive would be only $9.82/100 kg. CONCLUSIONS Based on the result of this study, the following conclusions were made: 1. National Research Council recommendations for energy were at least 25% too low for cows maintained under harsh climatic conditions, but are likely applicable to various types of cows under unstressed environments. 2. Increasing the energy level fed to cows did not increase efficiency (TDN/calf weaning weight). However, the ability of the cows to rebreed must be considered. 3. The larger framed AHC and AHH catt1e types were more efficient to weaning (TDN/calf weaning weight) than the smaller framed USH and SH types. 4. Nitrogen retention and net protein (percentage of nitrogen intake retained) values were higher for an 80% concentrate y§_a high si1age ration. 5. Retention of ration protein and metabolizability of ration energy were similar among cattle types and differences in digestive powers were small. 6. Steers gained 19% faster than heifers when fed a high si1age ration. Heifers tended to be less efficient in producing gain although differences were small when compared at similar carcass fat. 177 178 Carcass quality was similar when steers and heifers were compared at similar carcass fat. ME requirements for producing edib1e beef were similar among steers and heifers. Heifer quality may vary depending on the degree of culling practiced in the beef herd. Heifers were more favorable economically at lower prices of corn. Average daily gains were 29% greater for steers fed a 71% concentrate (HG) ration is those fed high si1age (HS). Average daily gains of USH, SH, and AHC steers were consistent with expectations based on frame size. However, Holstein crossbred steers gained at less than expected rates. Relative dry matter intakes (g/WkéS) were similar for all types of steers, and less than predicted for Holstein crossbred steers. Holstein crossbred steers performed relatively better on HS v§_HG rations. Based on the feedlot performance data, the primary effect of selecting for yearling weight was to increase frame size. Steers fed HG rations consumed more ME daily and produced heavier, fatter, higher quality carcasses. At simi1ar carcass weights within a cattle type, steers fed HG produced fatter carcasses a1though quality grades were similar. 17. 18. 15L 2C). 179 Marbling scores of Holstein crossbred steers compared favorably to beef breeds when compared at similar carcass fat. Increased rates of protein and fat deposition were noted with steers fed HG v§_HS rations, and were associated with increased ME intake and a greater proportion of ME available for productive purposes. Efficiency of utilization of ration protein and energy was less for Holstein crossbred steers than beef breeds. Efficiency of ME use for production of edible beef was not influenced by ration energy level. 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UmtcmEEoomL $0 NmNP .c0000002 x ecowmco: x 00002 ”00002 ”cowuuuuup ecu mucucmpcwus com 00mem 00 mpm>00 emecmEEoumc 000000 000:000 cucummm0 Pucowuuz ”0020 “222 mmwu—ogu20 x ecowmgm2 x 000:2 “022u 0.000 0.200 0.00 00-00-0 0 000 00.0 00.0 0.000 0.000 0000 2.000 0.200 0.02 00-00-0 2 000 00.0 00.0 0.000 0.202 0020 0.000 0.200 0.00 00-00-0 0 000 00.0 00.0 0.000 0.202 0000 0.000 0.200 0.02 00-00-0 2 000 00.0 00.0 0.002 0.000 0000 002 222 00 0.200 0.000 0.02 00-00-0 2 000 00.0 20.0 0.222 0.002 0000 0.000 0.000 0.02 00-00-0 2 200 00.0 20.0 0.000 0.000 0000 0.000 0.000 0.02 00-00-0 2 000 00.0 00.0 0.000 0.000 0000 2.020 0.000 0.02 00-00-0 0 200 00.0 00.0 0.000 2.000 0000 00002 222 00 0.000 0.000 0.02 00-00-0 2 000 00.0 00.0 0.002 0.002 0200 0.200 0.000 0.02 00-00n0 2 000 00.0 00.0 0.002 0.002 0020 0.200 0.000 0.00 00-00-0 0 000 00.0 00.0 0.002 0.000 0200 0.200 2.000 0.00 00-20-0 0 000 20.0 00.0 0.000 0.000 0200 0.000 0.000 0.00 00-0—-0 0 000 00.0 20.0 0.000 0.000 0000 00002 022 20 0.000 0.000 0.02 00-00-0 2 000 00.0 20.0 0.020 0.002 0020 0.000 0.000 0.00 00-00-0 0 000 00.0 20.0 0.200 0.000 0020 0.000 0.200 0.02 00-00-0 0 000 00.0 00.0 0.000 0.000 0200 002 022 00 00 .0ue 000 00 .0usuuu 00 .03 mpue x00 .02 Eu .uu0 so .uu0 00 .03 00 .03 .oz 0m>m0 0000 .0c 03 0c0cum: 03 0c0cumz 20c00 20c00 Fuc02 0u000c0 _uc00 0u000c0 020c0c0 um—00u0 cua uuue 00u0 uuue zo0 00 0u0c00 mm>0u0 ecu 0300 c_uum0o2 x eco0ucw2 x 000:2 ecu 00u0ocu20 x eco0wc02 x 000c2 cow uuu0 cowuweco0 ecu 020003 0u=e0>0ec0 2.2 000u0 Wind, km/hr Avg speed 184 mOl—VLOQNNLON mdopumeoéom MNwmmmmLfiMON soKoioommmoéd-vd; No. of days 2.25 21.27 22.54 'tation, cm 1p1 COP-ONOr—NOO NOt—Q'MNNMOP NQ’LOr—NLOLDQNLD F OOOOOOONOOO POOOPQ‘ONMNO NNMMNmI—DQLDO Table A.5 Climatic Conditions During Cow-Calf Trials (Trials 1,2) Trial 4.: cu '0 m c l_ 3 .0 m 25 moomr—ooooo qumNoooooo m :0 058- cuoaaaniu;c>c5c>c>c> oac>u>h~c>c>c>c>c>c>c> & 3 X1: PM“) I—NNr— o 0 c E (I) F 3 [\ONNMMQNMNLO NQVONd’OMLDNQ' o [\Nmzoxoow—r—q- NF-Nr-OO‘r—mwmm I- l—' 0'- co . o 0.0 v0 u—NNooooooo Oct-Nmooooooo r- I'— 5? . +313 V| : 0 g E: o o02NmmoooF mFFNwONoooo VI MMNNP— NMMNr—r- 0 a) s. .3 . <3 m2m~oooooo wmpmmoooooo f5 2.: VI f—N NM!— ; cum Q 44D N E, x - N ocooooor—r—F- oooooo—ooNo mo " :E c to N m NNoNxooanol— croooova—q-oom-zrp > NITOVdI—CF-(DLD ONFLOQ’ONNNC‘N < l PNNF’I— I lv—l r—F-F-Nr—F- I .C .Cr— .2!— +-’ U’I- QJ>5 4-’ U'I— QJ>5 4" : 0220;200:370. >u:.os.s.>,c.—cno. o 01000000:an 0000;000:000 z D'DLLE- I—r- r- r- 0 '— N l85 .00020ponsm 0:0 :000 new mafia 000pwm c000 NoN ”0: ”0:0E0F0000 mapa 000pmm c000 ”m:n .cw0umpo: x 0000000: x mamc< ”::< ”mm0Po0000 x 0000000: x mamc< "u:< ”0000000: 00000p0m "2m m00o0000: 00000p0mc0 ”:m00 m.mN 0.0m 0.0m N.oop m.va FN.0 a: mop N ::< m.mN 0.00 _.—N 0.NN 0.mmp 00.0 0: «NF N uz< m.NN 0.00 N.00 0.00 0.00p F0.N 0: 00_ N zm 0.0N 0.00 0.00 0.00 N.NNP NN.m 0: NNP N :m: <.ap 0.00 m.00 N._0 0.0mp 00.0 m: m0. N ::< N.FP 0.0F P.0m 0.Pm 0.NNP 0N.m m: MNF N uz< 0.N_ m.NN 0.00 0.00 c.0mp NN.0 m: oqp N :m 0.00 F.0m m.00 N.mN 0.—op 00.0 m: mN_ N :m: 0.00 0.00 0.00 o.Nm N.mmp om.N a: mv— _ ::< N.mm 0.00 N.Fm P._0 P.0NP 0m.N 0: mNF _ ux< 0.00 0.00 0.00 m.00 m.mmp 00.0 0: o¢p _ :m 0.00 m.mN F.NN 0.Pm _.00 FN.m a: mNp F :m: 0.00 N.Pm 0.00 0.Nm o.NOF P0.0 m: mop _ ::< 0.Nm N.Pm 0.00 0.00 0.00P 00.0 m: 0N— P ux< 0.0N F.0m 0.00 0.00 0.00P 00.0 m: cop F 0m 0.0m m.N0 N.o¢ 0.00 «.epp 00.0 m: NNP F :m: a x0mmm x0mmm xmwxm 000\m mm .000 ~0>0P .0: 000000 00x0 0000:? z\00:w0u00 2 00000000 2 z F0000 z 0:000 0000:? z .NM0\000000 0000 0000000 .Ewc< 00P000u AF —0w0hv 0000000 00000 cow: 0:0 0m0~wm :000 :00: 000 00000m 000 0000 00:0P0m 00000002 _0:0w>00cm 0.< 0—00h 1236 .0_0um—o: x 00000002 x 0:00< .0000000000 000 0000 000 0000 000—00 0000 RON “:10 0000—00000 x 0000000: x 0:00< “u:< 00000000: 00000000 .000000 000000 00 00 00 0000000000 "0: ”0000000000 0000 000000 0000 “0: 0 ”:0 "0000000: 0000000000 ”2000 000.0 000.0 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000\00uu 000\0000 000\0000 —000 00 .00 00>0P .00 000000 0000 000000 0000~0000000z 000000 000P0m0000 00000 0000000: 00000 1000\000000 0000 0000000 .0000 0000000 AP —0w0hv 0000000 =_~00 000: 0:0 moo—0m 0000 :00: 000 000000 000 0000 000.00-00000000 0:0 0000000000000 .mmmmo0 .000000 000000 _0000>00=0 0.0 0.000 187 .0005000000 000 0000 000 0000 000000 0000 00N “0: "0005000000 0000 000000 0000 “0:0 .0000000: x 0000000: x 00000 “::< 0000000000 x 0000000: x 00000 "0:0 "0000000: 00000000 ”:0 “0000000: 00000—0000 ”:000 0.0N 0.00 0.00 0.00 0.000 00.0 0: 00N N ::< 0.00 0.0N 0.00 0.00 0.000 00.0 0: 000 N 0:< 0.00 0.00 0.00 0.00 0.000 00.0 0: 00N N :0 0.00 0.00 0.0N 0.00 0.000 00.0 0: 00N N :00 0.0N N.00 0.N0 0.00 0.000 00.0 0: 00N N ::< N.0N 0.00 0.00 0.00 0.0N0 00.0 0: 00N N 0:< 0.0N 0.00 0.00 0.00 0.000 00.0 0: 00N N :0 N.00 0.0N 0.00 N.0N 0.00 00.0 0: 00N N :00 0.00 N.00 0.00 0.00 0.N00 00.0 0: 00N 0 ::< 0.00 0.00 0.00 0.N0 0.000 00.0 0: 00N _ 0:0 0.00 0.00 0.00 0.0N 0.0N0 00.0 0: 00N 0 :0 0.00 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00.0000N 00.0 0: 000 N ::0 000.N 000.0 00.0000 00.0000 00.000 00.0000N 00.0 0: 00N N 0:0 000.N N00.N 00.0N00 00.0000 00.000 00.0000N 00.0 0: 00N N :0 000.N 000.0 00.00N0 00.0000 00.000 0N.00_00 00.0 0: 00N N :00 000.N 000.0 00.NN00 00.00NN 00.0N0 00.0000N 00.0 0: 000 0 ::0 000.N 000.0 00.0000 0N.000N 00.000 00.0000N 00.0 0: 000 0 0:0 000.N 000.0 00.0000 N0.0000 00.000 00.0000N 00.0 0: 00N 0 :0 000.N 000.0 0N.0000 00.000— 00.000 00.00000 00.0 0: 00N 0 :00 000.N 000.N 00.00000 00.000N 00.0N0 00.0NO0N 00.0 0: 00N — ::0 000.N 000.N 00.0000 00.000N 00.000 00.0NO0N 00.0 0: 000 _ 0:0 0N0.N 000.0 00.0000 00.0000 00.000 00.000NN 00.0 0: 00N 0 :0 000.N N00.0 00.0000 00.0000 00.000 00.0—NON 00.0 0: 000 0 :00 0000000 0000w00 00000000 00000000 00000000 0000 00 JED, 00>00 .00 00_000 0000 000000 0000000000002 000000 0000000000 00000 0000000: 00000 0000000000 0000 0000000 .5000 0000000 00 ~00000 0000000 00000 000: 000 000000 0000 000: 000 000000 000 0000 0000000000000002 000 0000000000000 .000000 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