r g; 'e— — 7*” * ~ - - ~~~~---- THE ECONOMIC FEASIBILITY OF ; SUPPLEMENTING BROOD COWS AND YEARLING STEERS WITH PROTEIN. MINERAL-S AND VII'AMINS WHILE GRAZING FR'OSTED WINTER PASTURES ;' : Thesis Ior the Degree of M. S. I MICHIGAN STATE UNIVERSITY fl CHARLES KELLER ALLEN f 1972 LIBRARY "II-I. Michigan State University ABSTRACT THE ECONOMIC FEASIBILITY OF SUPPLEMENTING BROOD COWS AND YEARLING STEERS WITH PROTEIN, MINERALS AND VITAMINS WHILE GRAZING FROSTED WINTER PASTURES BY Charles Keller Allen Three grazing trials and two nitrogen balance trials were conducted concurrently to test the value of two commer- cially available liquid supplements for supplementing cows and steers while grazing winter pastures in Argentina. Two types of pasture, Agropirum elongatum (agropero) and leoti £29 (sorghum), were used. Two supplements, one containing 35% crude protein equivalent having 80% derived from urea and 20% pre-formed protein sources, "Pro-Lix", and one con- taining 30% crude protein equivalent having 100% derived from urea, "Rico—30", were compared to a control (no protein supplement). A total of 250 yearling steers were assigned to five treatment groups. Three of the five groups were assigned to sorghum pastures and the other two groups assigned to agro- pero pastures. "Pro-Lix", "Rico-30" and a no supplement con- trol were fed to the steers grazing sorghum while only “Pro— Lix" and the control treatments were used with agropero pas- tures. Almost all of the yearling steers grazing sorghum lost weight during the experiment. The "Pro-Lix" steers lost the Charles Keller Allen least weight and the control steers had the greatest losses. All of the differences among treatments in total weight loss were significant (P < 0.05). The agropero steers gained weight during the experiment. The control steers outgained the "Pro-Lix" steers during the first half of the experiment but this advantage was more than offset by the significantly higher (P < 0.05) weight gains of the "Pro-Lix" steers during the last half of the experi- ment. Thirty lactating Angus cows and 20 non-lactating Angus cows were assigned to each of the three supplements ("Pro- Lix", "Rico-30" and control) and grazed on adjacent sorghum pastures. There was virtually no difference in weight changes of the non-lactating and lactating cows regardless of whether they were supplemented or not. However, the calves nursing cows receiving "Pro-Lix" supplement gained signifi- cantly more weight (P < 0.05) than the calves in either the "Rico-30" or control groups. The plasma carotene and vitamin A levels were used to predict the vitamin status of a random sample of animals in each group. The mid-experiment and final blood collections were taken from the same animals selected at the beginning of the experiment. There were no significant differences among the different supplemental groups for any of the plasma vita- min A analysis. The plasma carotene concentration of the agropero control steers was significantly (P < 0.05) higher than "Pro-Lix" steers on the same pasture. Although not Charles Keller Allen significant, there was a trend for the plasma carotene con- centration of the controls to exceed the carotene level of the supplemented animals in all experiments. The nitrogen balance of the control treatment was neg- ative for both the agropero and sorghum forages. The dry- matter intake was greater for the supplemented steers on both forages, but only the differences on agropero were sta- tistically significant (P < 0.05). There were no signifi- cant differences among any of the supplements for drymatter digestibility. THE ECONOMIC FEASIBILITY OF SUPPLEMENTING BROOD COWS AND YEARLING STEERS WITH PROTEIN, MINERALS AND VITAMINS WHILE GRAZING FROSTED WINTER PASTURES by .jCharles_Keller Allen A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Animal Husbandry 1972 Charles Keller Allen candidate for the degree of Master of Science DISSERTATION: The Economic Feasibility of Supplementing Brood Cows and Yearling Steers with Protein, Minerals and Vitamins while Grazing Frosted Winter Pastures OUTLINE OF STUDIES: Major Area: Animal Husbandry (Ruminant Nutrition) Minor Subject: Biochemistry BIOGRAPHICAL ITEMS: Born: December 15, 1942; Independence, Virginia Undergraduate Studies: Virginia Polytechnic Institute, 1965-1969 Graduate Studies: Michigan State University, 1969-1972 MEMBER: American Society of Animal Science ii ACKNOWLEDGMENTS The author extends his deep appreciation to Dr. Hugh E. Henderson for his valued guidance and counsel during his graduate program. The author is also indebted to Dr. William T. Magee and Dr. Richard W. Luecke, as members of his graduate com- mittee, for their sound advice and participation in his gra- duate program. The author also wishes to thank Dr. Ronald H. Nelson and Dr. J. A. Hoefer for making the facilities of Michigan State University and the Michigan Agricultural Experiment Station available for this research. Appreciation is extended to all members of the Depart- ment of Animal Husbandry for their kindness and hospitality. The author is indebted to ProRico Industries of Mobile, Alabama, for providing the materials used and for providing the author's expenses during the course of this research. The author is also indebted to Dr. Raul Haumfiller of Rosario, Argentina and Sr. Raul Firpo of Buenos Aires for their assistance in conducting this research and for pro- viding the cattle and facilities used. iii TABLE OF CONTENTS List of Tables List of Figures I. Introduction II. Literature Review Use of Frosted Winter Pastures Urea as a Protein Supplement Self-Feeding Vitamin A Summary III. Materials and Methods Experiment 1 - Supplementation of Steers Grazing Sorghum (leoti redY Pastures Design Method of Supplementation Pasture Management Carotene and Vitamin A Determination Experiment 2 - Supplementation of Steers Grazing Agropero (Agropirum elongatum) Pastures De51gn Method of Supplementation Pasture Management Experiment 3 - Cows and Calves Grazing Sorghum Pastures Design Method of Supplementation Pasture Management Experiments 4 and 5 - Nitrogen Balance Studies DeSign Facilities Feeding Regime and Sample Collections Laboratory Analysis Statistical Analysis iv ‘Page vi vii l7 l7 17 20 20 20 21 21 22 22 23 23 23 23 23 24 25 25 25 26 27 27 Table of Contents (Cont.) IV. Results and Discussion Experiment 1 - Steers Grazing Sorghum Pastures Supplement and Feed Intake Weight Changes Plasma Carotene and Vitamin A Concentrates Experiment 2 - Steers Grazing Agropero Pastures Supplement and Feed Intake Weight Changes Carotene and Vitamin A Experiment 3 - Cows and Calves Grazing Sorghum Pastures Supplement and Feed Intake Weight Changes of Non-Lactating Cows Weight Changes of Lactating Cows Weight Changes of Calves Carotene and Vitamin A of Cows Experiments 4 and 5 - Nitrogen Balance Studies Feed and Supplement Analysis Drymatter Intake and Digestibility Nitrogen Balance V. Summary Bibliography 38 39 4O 43 46 47 48 50 52 54 56 56 58 58 61 65 Table 10 ll 12 13 14 15 l6 l7 1&3 LIST OF TABLES Analysis of Supplements Used Ingredients of the Supplements Used Analysis of Pro-Lix Mineral Number of Animals Starting and Finishing Experiment and Reasons for Removal from Experiment Crude Protein Levels Found in Representative Samples of Experimental Pastures Supplement Consumption of Animals in Experiments 1 through 3 Weight Changes of Steers on Sorghum Pasture Cost of Supplement Necessary to Make Supple- mentation Profitable for Steers Wintered on Sorghum Plasma Carotene and Vitamin A Concentrations of Sorghum Steers Weight Changes of Steers on Agropero Pasture Cost of Supplement Necessary to Make Supple- mentation Profitable for Steers Wintered on Agropero Plasma Carotene and Vitamin A Concentration of Agropero Steers Weight Changes of Non-Lactating Cows Weight Changes of Lactating Cows Weight Changes of Calves Carotene and Vitamin A of Cows Drymatter and Crude Protein Levels of Forage and Supplements Offered and Forage not Con- sumed by Cattle on Nitrogen Balance Studies Actual Treatment Means for Metabolic Study vi "Page l6 16 18 29 30 31 33 35 36 41 43 44 49 51 53 55 57 59 LIST OF FIGURES Figure Page 1 Supplement Feeder Used for Sorghum Steers and Cows I 19 2 Wheel Type Feeder Initially Used for Agro- pero Steers 22 3 One of the 6 Collection Stalls Used in the Metabolic Studies 25 vii I . INTRODUCTION Argentina is one of the great agricultural producers and exporters of the world. It is the world's leading sup- plier of beef and accounts for approximately 7.5% of the beef exports. Argentina is also a strong competitor in international markets for meat products, hides and animal fats. During the ten years from 1956 to 1965, the export of beef, cattle hides and live cattle accounted for 24.9% of the average annual value of total Argentine exports. There was approximately 47 million cattle in Argentina in 1966. These cattle provided beef and dairy products for a population of 22.85 million and contributed approximately 25% of the total exports. Total food production in Argen- tina increased 20% from the 1952-56 average until 1966, but the per capita food production actually declined 2% during that same period. The agricultural resources of Argentina are extensive and varied. The country extends south from a latitude of 210 46' 55". It is 2,300 miles long and 884 miles wide at the widest point. The total land area of continental Argen- tina is 279.2 million hectares, of which 175 million hec- tares or 63% is in farms. Average annual rainfall and sea- sonal temperatures are extremely varied among different areas. The mean annual rainfall ranges from 10 cm at San Juan in the northwest to 165 cm at Posadas in the northeast. The mean July and January temperatures for different regions range from 25° to 62° F. and from 490 to 830 F., respectively. Only 24% of the land area is classified as humid, while 15% is considered semi—arid and 61% arid. The most productive agricultural area in Argentina is the Pampa. This is the predominant crop area and also con- tains over 80% of the country's cattle. The Pampa corres- ponds to a rough semicircle with a radius of about 550 kilometers around the city of Buenos Aires. The Pampa is naturally divided into two parts, humid and semiarid, accounting respectively for 63 and 37% of the regional area. Beef production is very extensive and Argentina's beef potential is much greater than present production. Sixty- three percent of the land in farms consist of natural pas- ture with only 6% of the farmland comprised of improved pastures. Presently, almost all slaughter cattle are fin- ished on grass and go to market between two and three years of age. On a typical estancia or ranch in the Pampa, the brood cows and yearling steers are Wintered on low quality frosted grass pastures without supplementation. The yearling cattle usually lose weight during the winter. The average calving percentage of the cows is approximately 60% or in herds that breed cows all year, the average calving interval is about 15 months. It was hypothesized that economic production traits could be greatly enhanced if cattle grazing frosted winter pastures had access to a supplement formulated to correct the nutritional deficiencies of the winter pasture. Therefore, the objectives of this study were: 1) To test the above stated hypothesis; 2) To determine the nutritive value of frosted grass pastures; 3) To compare the relative value of two different sources of supplemental protein -- one having 100% of its crude protein equivalent derived from urea and the other, 80% from urea and 20% from organic sources of protein; and 4) To determine changes occurring in blood serum levels of vitamin A and carotene. II . LITERATURE REVIEW The use of frosted winter pastures as a source of win- ter feed in the United States has been limited primarily to the western states and to native bluestem pastures. Pinney 35 al. (1962c) reported that samples of native grasses con- sistently showed that the forage produced during the winter period is deficient in energy, protein and phosphorus. They found that by December, native grass in Oklahoma had lost 80% or more of the protein and phosphorus it contained during early growth. A study during 1942 and 1943 showed that the percent protein in the drymatter of native bluestem grass declined from a high of 9% in May to a low of 2.6% in Feb- ruary (Hobbs et_§l, 1945). Wallace gt 31. (1970) found that the diets of cattle grazing pastures in the sand hills of Colorado were deficient in digestible protein and marginal in metabolizable energy in September. By December, the diet was grossly deficient in both energy and protein. In contrast to Argentina, protein supplementation of cattle on winter pasture is a common practice in the United States. Hobbs et_al. (1945) reported that supplements of cottonseed cake not only provided adequate protein but also increased the digestibility of the forage. Campbell at El. (1969), in a nitrogen balance study, found that the digesti- bility of the organic matter, crude protein, nitrogen free extract and gross energy in the total ration increased with 5 higher levels of natural protein. Several other workers have observed an increase in digestibility following a more liberal feeding of protein supplements to ruminants (Swift gt gl., 1947; Gallup and Briggs, 1948; Burroughs gt_gt., 1949). Wintering pregnant or lactating cows on native grasses and very low levels of supplement has been shown to increase cow weight losses, decrease weaning weights, delay the ave- rage calving date and decrease the percent calf crop (Pinney gt gt., 1962a; Nelson gt gt., 1962; Speth gt gt., 1962; and Ludwig gt gt., 1967). Nelson gt_gt. (1962) also found that cows wintered in a trap on prairie hay performed better than cows grazing dry grass. In addition, Pinney and associates (1962b) reported that the producer who feeds out his own calves (as is common in Argentina) would profit by not win- tering their dams on an extremely low level. Meyer gt gt. (1965) reported that compensatory gain offset some of the disadvantages incurred by wintering steers on a low energy level immediately after weaning. However, the total energy requirement was higher and the total days required to slaughter was greater for the low level group. Steers in this study wintered on the low level diet did not lose weight as is common with steers wintered in Argentina. Urea as a Protein Supplement Feeding trials with cattle (Bartlett and Cotton, 1938; Hart et al., 1939; Rupel gt gt}, 1943; Willet gt_gl3, 1946; Briggs gt_gl,, 1947; Dinning gt gt., 1949; and Brown‘gt'gt., 1956) have demonstrated the usefulness of urea as a nitro- genous supplement for partially meeting the protein needs of ruminants. Nitrogen balance experiments (Harris and Mitchell, 1941; Johnson gt'gt., 1942; Harris gt gt., 1943; Hamilton gt gt., 1948 and Arias gt gt., 1951) have added further information showing that limited amounts of urea can be converted into useful protein. Urea is particularly suited as a feed ingredient since it is economical, odorless mater- ial of high nitrogen content and biological availability (Belasco, 1954). Numerous studies at the Michigan Station (Henderson gt gt., 1960; 1968a; 1968b and 1970) have shown that urea can not only replace part of the supplemental protein but also substantially reduce the total feed cost for feedlot steers. Other workers (Ewing and Burroughs, 1963 and Martin gt gt., 1968) have shown that urea can also be used in the rations of breeding cattle to reduce feed cost without sac- rificing optimal performance. In contrast, experiments in Oklahoma have shown that urea is not as efficiently utilized as natural proteins for wintering cattle on native grass. This was true for both steers (Nelson gt gl,, 1961) and lactating cows (Miller gt gt., 1958; Williams gt gt., 1968). Williams and co- workers (1968) thought that the reason that previous Okla- homa work had failed to show good urea utilization was due to the low level of energy in the ration. New1and‘ t E:- (1961) reported a slight depression in gains and feed efficiency when urea made up 100% of supplemental protein. In order to make the most efficient use of urea as a nitroqen supplement to poor quality roughages, a readily available source of carbohydrate appears necessary (McKnaught and Smith, 1947; Bell gt gt., 1953; Reid, 1953; and Belasco, 1956). Arias gt gt. (1951) reported that increasing the energy content of the fermentation mixture resulted in an increased urea utilization with all sources of energy tested. This was true regardless of whether the energy source was a soluble carbohydrate such as dextrose or sucrose, or whether the carbohydrate was more complex such as the cellulose of a high fiber feed. It was observed that small amounts of a readily available carbohydrate aided cellulose digestion, which in turn increased urea utilization, whereas large amounts of readily available carbohydrate, inhibited cellu- lose digestion. Burroughs gt gt, (1950) found cane molasses to exert a favorable effect on the digestion of cellulose in an artifi- cial rumen. Willet and gt gt. (1946) found that when cane molasses constituted 25% of the concentrates in the ration of the dairy cow, urea was utilized very efficiently. Bowstead and Freedon (1948) reported that molasses was essen- tial for the utilization of urea included in the rations of their dairy cows. Tillman gt gt. (1951) reported that ani- mals receiving liquid molasses made satisfactory gains while those receiving dehydrated molasses did not make satisfac- tory gains. However, Mills and associates (1942, 1944) reported that starch and the cereal grains were more desir- able than sugar (molasses) as a source of carbohydrates in urea containing rations. Gallup gt gt. (1954) compared the additions of urea and soybean meal to a high molasses ration and found that both additions improved digestibility and nitroqen retention. However, the soybean meal addition had the greatest effect. Blackstrap molasses fed at the level of 10% of drymatter intake to fattening cattle was efficiently utilized, but increasing the level of molasses to 20% or above caused a marked depression on feed consumption, weight gains and net energy values (Lofgreen and Otagaki, 1960; and Lofgreen, 1965). The superiority of starch over molasses tg_ytytg_may mean that simple sugars tend to be washed out of the rumen or to be absorbed more rapidly than the less soluble poly- saccharides, resulting in less exposure to the micro-organisms. On the other hand cellulose (an insoluble polysaccharide) is probably attacked too slowly to make it a ready source of energy for microbial multiplication (McKnaught and Smith, 1947). The relative cost of different grains and other high energy sources must be considered when formulating a prac- tical supplement. Molasses is a very inexpensive (2 to 3 cents per kilogram) source of energy in Argentina (Haumfiller, 1969). Detailed discussions of the carbohydrate component of urea rations can be found in comprehensive reviews by McKnaught and Smith (1947), Owen (1951) and Arias (1951). Johnson gt Ei' (1942) reported that supplements containing corn molasses depressed the digestibility of the ration but enhanced the utilization of urea. Bell gt gt. (1953) re- ported the efficiency of urea utilization was lowest when fed with molasses and was approximately equal when fed with the various cereal grains and sweet potatoes. Tillman gt gt. (1951) combined urea with liquid molas- ses and reported that urea did not alter the palatability of the molasses. The urea-molasses treatment group had gains and feed efficiencies that were slightly below the corn-cottonseed meal control group. However, the differ- ences were not significant (P < 0.05). Commercial liquid supplements composed of molasses, urea, phosphorus, trace minerals and vitamins were first introduced to the United States in 1951 (Beeson and Perry, 1970). Feedlot test with beef steers by Perry gt gt. (1967), Gay and Vetter (1967) and Kercher and Paulus (1967) have shown no significant difference in the nutritive value (as measured by cattle reSponse) to high—urea solid or liquid supplements when the supplements and/or rations contain the same essential nutrients in the proper balance. Beeson gt gt. (1964a and 1964b), Beeson and Perry (1969) and Perry and Beeson (1968) reported the existence of uniden— tified urea protein factors (UPF). The addition of both dehydrated alfalfa meal and distillers grain solubles increased nitrogen retention, feed efficiency and average 10 daily gain (Beeson and Perry, 1969; Beeson gt gt., 1968 and 1969; and Perry gt gt., 1969). In other work, Beeson and Perry (1969 and 1970) verified the effectiveness of dehy- drated alfalfa meal on increasing urea utilization in liquid supplements. Perry gt gt. (1969) found a slight but non-significant increase average daily gain by adding fish solubles to a high urea liquid supplement. Burroughsgt gt. (1969) also reported improved performance when fish solubles were added to high urea liquid supplements, but found no advantage to adding fish solubles to high urea dry supplements. Self—Feeding Labor requirements and cost can be decreased if the intake of supplements can be regulated so they may be self fed. Weir and Miller (1953) compared a self—fed mixture of 25% salt and 75% cottonseed meal to an equal amount of cot- tonseed meal fed to ewes under drylot conditions. There was no difference in the performance of the ewes or their lambs and no evidence of salt toxicity. A later trial con- ducted under range conditions and utilizing the same supple- ments (Weir and Torrell, 1953) gave similar results. Riggs gt gt. (1953) reported that salt-cottonseed meal mixtures for beef cows had no adverse effects and that a higher salt intake may have a beneficial effect upon the digestibility of all nutrients. Currently, many of the liquid supplements available ll commercially use phosphoric acid both as a source of phos- phorus and to regulate intake. Phosphoric acid was first introduced into liquid supplements in 1896 when Goldby, a British scientist, obtained a patent on a liquid feed con- taining a combination of beet molasses and phosphoric acid (Beeson and Perry, 1970). Menzies gt gt. (1955) conducted studies with steers using a mixture of molasses and phosphoric acid to supply small amounts of energy and phosphorus. Their studies in- dicate that phosphoric acid has a high biological availabil- ity for cattle. Bhattacharga and Warner (1967) demonstrated the ability of phosphoric acid to significantly reduce the intake of supplemental feed. Vitamin A The importance of vitamin A as a nutrient in all classes of livestock has been reported by many research workers. Watkins gt gt, (1950) stated that vitamin A deficiency will develop in range cows on typical western ranges only after periods of prolonged drought. However, Riggs (1940), work- ing with young cattle on diets devoid of carotene and vita- min A, reported depletion of vitamin A stores in as little as 46 days. It has long been recognized that aging, weather- ing and bleaching of forages destroys the carotene and/or vitamin A (Flora, gt gt,, 1939). Some of the most obvious vitamin A deficiency symptoms, from an economic point of view, are blindness, reproductive 12 impairment and decreased rate of gain. Numerous studies (Guilbert and Hart, 1935; Flora'gt_gt., 1939; Sutton gt gt., 1940; and Hodgson gt gt, 1964) have shown that blindness and/or reproductive impairment can result from vitamin A deficiency. Sutton and associates (1940) also noted a marked decrease in the incidence of pneumonia when calves on a diet deficient in vitamin A or carotene were fed supple- mental vitamin A. In addition, supplemental vitamin A has also been shown to increase weight gains when rations are marginal or deficient in vitamin A (Beeson gt gt, 1961; Smith gt gt., 1961; Perry gt gt., 1962; and Chapman gt_gt., 1964). Although vitamin A addition to the ration does not always increase performance (Weichenthal et al., 1963) it is a relatively inexpensive nutrient and is frequently inclu- ded in the ration when there is doubt about the vitamin A status of the animals in question. Several workers have indicated that vitamin A defi- ciency could be diagnosed by blood analysis (Moore, 1939; Davis and Madsen, 1941; Kuhlman and Gallup, 1942; Braun, 1945; and Pope gt gt., 1958), or that there was a direct or indirect relationship between plasma and hepatic vitamin A levels (Frey gt‘gt,, 1947; Hoefer and Gallup, 1947; Almquist, 1952; and Rousseau gt gt., 1958). However, Ralston and Dyer (1959), after studying bovine plasma and hepatic vitamin A levels in several areas of the state of Washington, con— cluded that hepatic stores of vitamin A could not be deter— mined by plasma analysis alone. In addition, Bodansky and l3 Markart (1951) found measurable amounts of vitamin A in rat plasma although the liver was entirely depleted. Wheeler gt gt. (1957) reported that pregnant cows accumulate large stores of vitamin A when grazing spring range which will supply their vitamin A needs during winter even though very low levels of carotene and vitamin A are available in their winter rations. However, they speculated that vitamin A deficiency might occur in young calves that are nursing their dams when they are not permitted to con- sume at least small quantities of hay or other carotene bearing feeds. Studies by Guilbert and Hart (1935) and Baker gt gt. (1953) showed that cows with low liver stores maintained on a low carotene diet were unable to secrete sufficient vita- min A in the milk to protect their nursing calves against avitaminosis A. In a follow-up experiment, Baker gt gt. (1954) found that the vitamin A content of the milk seemed more closely related to dietary carotene intake during lac- tation than to differential liver stores resulting from var- ious levels of carotene intake preparturition. It appears that ruminant animals are poor converters of carotene to vitamin A (Tillman, 1962). Similarly, Myers gt gt. (1959) reported that there was a greater storage response to vitamin A than to carotene. Therefore, it is logical to provide supplemental compounds in the form of Vitamin A rather than in the form of carotenoids. 14 Summary Poor quality, weathered forages have been found to be deficient in energy, protein, phosphorus and vitamin A. The performance of cattle can be improved by proper supplementa- tion of these nutrients. Although performance may be max- imized by using cereal grains and natural protein, supple- ment cost may be greatly reduced by utilizing urea and molasses. Liquid high urea supplements have been found to have equal feeding value to dry high urea supplements as long as both rations contain the same nutrient balance. Perform- ance of cattle on high urea rations may be improved by the addition of dehydrated alfalfa, distillers solubles or fish solubles as a source of unidentified—urea protein fac- tors (UPF). Self—feeding supplements with an ingredient such as salt or phosphoric acid added as an intake control has been reported to give equal performance without any harmful side effects. In addition, phosphoric acid has been shown to be a readily available source of phOSphorus. The performance of cattle can be improved by providing adequate intakes of vitamin A unless they already have suf- ficient hepatic stores. The performance of nursing calves :may be improved by providing them or their dams with an adequate intake of vitamin A or carotene. III. MATERIALS AND METHODS Three grazing trials and two nitrogen balance trials were conducted concurrently to test the value of two commer- cially available liquid supplements for supplementing cows and steers while grazing winter pastures in Argentina. The supplements used were supplied by ProRico Industries of Mobile, Alabama, and are sold under the trade names of "Pro- Lix" and "Rico 30". The ingredients and analysis of these supplements are shown in Tables 1 and 2. Funds for travel and other expenses associated with this study were provided by ProRico Industries. The trials were initiated just after the first frost in the fall of 1969 and were terminated when the grass turned green in the spring of 1969. The grazing experiments involved 150 Angus cows, 90 of them with calves, and 250 Angus steers on two types of pasture. The two nitrogen balance studies were 3 x 3 latin squares using three steers each, three supplements each and two different forages. All of the cows included in the grazing trials were maintained on native pastures 30 to 60 days prior to the experiment. The experimental steers were maintained on corn aftermath pastures for 60 days prior to the experiment. Materials and methods are presented under experimental headings. 15 16 Table 1.nnAna1ysis of Supplements Used t‘ir-‘Y.T“ Vw..v*rw ‘- Y Vfi w v - YVVV fl Nutrient. Pro~Lix Rico-3O Crude Protein, minimum 35.0 % 30.0 % Protein Equivalent from NPN, max. 27.0 % 28.0 % Fat, minimum 0.70 % --- Fiber -—— --- Sugar (invert), minimum 35.0 % 35.0 % Vitamin A (U.S.P. units/mg), min. 44.0 38.5 Vitamin D (U.S.P. units/mg), min. 11.0 11.0 Vitamin E (I.U./kg), minimum 30.3 30.3 Calcium, minimum 0.52 % 0.52 % Phosphorus, minimum 0.51 % 0.51 % Phosphorus, maximum 1.50 % 1.50 % Cobalt, minimum 0.0003 % 0.0003% Copper, minimum 0.006 % 0.006 % Iron, minimum 0.02 % 0.02 % Magnesium, minimum 0.22 % --- Manganese, minimum 0.0008 % —-- Zinc, minimum 0.00085% —P- Iodine, minimum 0.00025% r-r Ash, maximum 10.0 % 10.0 % Table 2.--Ingredients of the Supplements Used Ingredients in Both Pro-Lix and Rico—30 Ingredients in Pro-Lix Only Molasses Fish Solubles Urea Fermentation Solubles Phosphoric Acid Brewers Yeast Vitamin A Palmitate Manganese Sulfate D-Activated Plant Sterol (D2) Zinc Sulfate Copper Sulfate Ethylene Diamine Dihydroiodide Cobalt Sulfate l7 Experimentxl as Supp1Ementation of Steerstrazing Sorghum '\“1‘.1'\1 ‘terfiffi'W-z‘KV‘VWiwxfi (leoti tgd) Pastures rvrfiwvvfi Design: A total of 250 steers were randomly assigned to five groups 60 days prior to initiating the experiment. At the beginning of the experiment all steers were indivi- dually weighed and identified. The first 50 steers were assigned to one group, the next 50 were assigned to a second group and the process continued until 50 steers had been assigned to each of five groups. The steers were iden- tified by both the neck tag number and numerical brands. Three of the five groups were assigned to sorghum pas- tures and the other two groups were assigned to agropero (Agropirum elongatum) pastures. The three sorghum groups were randomly assigned to one of three supplements: "Pro- Lix", "Rico-30", and a no supplement control. Each treatment group was then randomly assigned to one of three adjacent sorghum pastures of 50 hectares each. Method of Supplementation: All experimental animals were offered a "Pro-Lix" mineral supplement for 60 days prior to the initiation of the experiment. The guaranteed analy- sis of this mineral mix is shown in Table 3. After the experiment was started, all the groups receiving liquid sup- plements were continued gg libitum on "Pro-Lix" mineral mix. On August 15, the "Pro-Lix" mineral mix was depleted and the cattle were changed to a mineral supplement of one-half salt and onevhalf bone meal. The liquid supplement was fed gg libitum for the first 18 Table 3.n—Ana1ysis of Pro—Lix Mineral Ingredient Quantity Phosphorus, minimum 15.00 % Calcium, minimum 15.00 % Calcium, maximum 18.00 % Sodium Chloride, minimum 9.00 % Sodium Chloride, maximum 10.00 % Magnesium 0.50 % Sulfur 0.20 % Zinc 0.15 % Manganese 0.20 % Copper 0.02 % Iodine 0.01 % Iron 0.25 % Cobalt 0.02 % Fluorine 0.19 % Mineral ingredients 91.75 % Vitamin A (U.S.P. units/mg) 220.3 Vitamin D (U.S.P. units/mg) 56.1 Vitamin E (I.U./kg) 110.1 19 three weeks in a feeder identical to that shown in Figure 1. After the first three weeks, the amount of supplement was regulated by gravity—flow from the storage tank to the feed pan below. Enough supplement was dispensed every other day to amount to approximately 900 grams per steer per day. l_—~_»r- —_.— Figure l.--Supplement Feeder Used for Sorghum Steers and Cows 20 ~Pasture: The sorghum pasture had been previously grazed to the extent that there was very little grain remaining. The forage was badly weathered and very little of it was still standing. Forage samples were taken for laboratory analy- sis on July 1, August 15 and October 1. Representative samples were taken from various areas of the field and pooled at each sample date. Samples were tho- roughly mixed, subsampled and ground in an electric blender. The sample was then analyzed for crude protein by the micro- Kjeldahl procedure. Drymatters were determined by oven drying the forage at 110°C for 24 hours. Original plans called for a carotene analysis of all forage samples. However, this was not possible because of insufficient equipment and the extensive treatment required to bring forage samples back to the United States would have destroyed most of the carotene present. Management: The steers were weighed on June 26, August l4 and September 30. All weights were taken after the steers had been corralled overnight without feed or water. All animals were vaccinated for Aftosa and Anthrax during the experiment. They were also sprayed twice at a 14—day interval for external parasites. Carotene and Vitamin A Determination: Jugular blood samples were taken from the first 15 steers from each treat- ment group as they came through the chute at the time of the first weighing. Additional blood samples were taken from the same steers at the second and third weighing. To prevent 21 clotting, 2 ml of heparin were added to each blood sample and mixed thoroughly. The samples were then chilled and taken to a laboratory in Rosario (approximately 250 kilometers) before being centrifuged and the serum separated with a Pasteur type pipet. The serum was immediately frozen and held for less than 30 days before it was analyzed for carotene and vitamin A. After thawing, 3 m1 serum were treated with absolute ethanol and the carotenoids and vitamin A were extracted with petroleum ether. The sample was then centrifuged, an aliquot taken, and the percent absorbance determined at 440 nm on the Spectronic 20. The concentration of carotene was deter— mined from a standard curve of B-carotene. Each sample was duplicated. The ether was evaporated by use of a vacuum oven at 60°C and the vitamin A concentration determined by utilizing the color reaction of Carr and Price (1926). The vitamin A and carotene was dissolved in chloroform, antimony trichloride was added and the percent absorbance read immediately at 620 nm. The concentration of vitamin A was determined from a stand- ard curve of vitamin A acetate. Experiment 2 —+ Supplementation of Steers Grazing Agropero (Agropirum elongatum) Pastures Design: The two groups of steers assigned to agr0pero pasture were randomly assigned to one of two supplements: "Pro—Lix" and a no supplement control. They were then 22 randomly allotted to one of two adjacent 50 hectare pastures. After the mid—experimental weight was taken, the pastures were alternated to minimize pasture effects. Method of Supplementation: Mineral supplementation was the same as for the sorghum steers. The liquid supplement was first offered in the wheel type self—feeder shown in Figure 2. However, it was difficult to get steers started on the wheel type feeder and their daily consumption was very low. The agropero steers were changed to the feeder shown in Figure 1 after two weeks and the supplement was fed 3g libitum from this feeder for the remainder of the trial. Pasture: The agropero pasture had not been grazed during the previous six months and there was an excessive amount of forage available. Pasture samples were taken and analyzed in the same manner as described in Experiment 1. Figure 2.--Whee1 Type Feeder Initially Used for Agropero Steers 23 Mapggement: The management and determinations of plasma vitamin A and carotene concentrations were identical to that described for Experiment 1. Experiment 3 -— Cows andCalves GrazingfiSorghum Pastures Design: A 3 x 2 factoral design was utilized to study the effect of providing supplement to cows on winter pasture. The same three treatments were used for cows as for the sor- ghum steers in Experiment 1. Thirty lactating Angus cows with calves and 20 pregnant Angus cows were randomly assigned to each treatment group in the same manner as described for the steer groups. The three groups were then assigned to one of three adjacent 50 hectare pastures. Since there appeared to be a difference in the quantity of forage in the three pastures, the cows were rotated from one pasture to another every two weeks to minimize pasture effects. Method of Supplementation: The liquid supplements were fed gg_1ibitum for the first two weeks and consumption was in excess of 1 kg per cow per day. After the first two weeks supplement consumption was regulated to approximately 900 grams per cow per day and 225 grams per calf per day. The same type of feeder was used for the cows as described for the sorghum steers (Figure 1) and the cow groups were provided minerals in the same manner as the sorghum steers. Pasture: The pasture had been managed the same and was very similar to the sorghum that the steers grazed in Experiment 1. Pasture samples were taken and analyzed in 24 the same manner as described for the sorghum steers. Management: The cows were weighed on July 1, August 15 and October 1. All weights were taken after the cows had been separated from water and feed overnight. Jugular blood samples were taken from the first eight lactating and the first seven pregnant cows to come through the chute at the time of the first weighing. Blood samples were taken from the same cows on the second and third weigh dates. All blood samples were treated as described in Experiment 1. There were no records as to which calf belonged to a particular cow and the calves had to be separated by obser— vation. During this process, six calves were either lost or failed to be identified. The cows whose calves were never found were carried through the experiment and their perform~ ance was analyzed along with the pregnant non-lactating cows. On July 5, the cows and calves were brought back to the corral in groups. The calves were weighed and identified with a neck tag of the same color as their dams. A cow and her offspring were paired as the calves nursed after they had been separated from their dams overnight. The second and final weights of the calves were taken on the same day that the cows were weighed. The spraying and vaccination of the cows and calves were done on the same days and in the same way as for the sorghum steers. 25 Experiments 4 and§ :3 Nttrogen Balance StudiES Design: A 3 x 3 latin square design was utilized for a nitrogen balance study on both agropero and sorghum forages. The trial was initiated on August 3 and terminated on October 6. Six yearling Angus steers averaging 231 kg at the start of the trials were utilized in these experiments. ‘Io. G7,. '. Figure 3.—-One of the 6 collection stalls used in the metabolic studies. Facilities: Six individual stalls (Figure 3) were con- structed for the nitrogen balance studies. They were approx- imately 60 cm wide and 200 cm long. The feed container was made by placing a partition across the concrete floor of the stall, 45 cm from the front. A recessed area was placed in the center of the stall floor. The reCessed area sloped sharply and served to catch urine and deliver it to a screen 26 covered plastic bucket outside the stall. The steers were kept in the stalls for 3 weeks at first to adjust them to the conditions and to the presence of men. They were then returned to pasture for two weeks while final modifications were made on the stalls. When the steers were returned on August 3, they started their first two week adap- tation period to the diet. The first week was spent in a ten meter by ten meter pen, after which they were moved to the collection stalls for another week of adaptation and a week of collection. Each animal occupied the same stall throughout the experiment so that the stall effects were confounded with animal differences. Feeding regime and sample collections: The steers were fed roughage (agropero or sorghum) gg libitum. The feed con- tainers were filled at 8 a.m., 11 a.m., 2 p.m. and 5 p.m. daily. The unconsumed forage was removed, sampled and weighed on both the third and final day of collections. The forage fed was collected weekly throughout the ex- periment from experimental pastures used in the grazing trials. The forage was harvested or collected by hand and stored in burlap sacks. Samples were taken from each sack of forage as it was weighed. All sorghum samples were pooled for one period and subsampled for lab analysis. The agro- pero samples were handled in an identical fashion. Total fecal collections were made by collecting the feces after it had dropped to the concrete floor of the' stalls. The feces was collected the first thing every 27 morning and throughout the day. Feces were stored in a bucket until they were weighed and a sample taken for lab analysis each morning. Total urine excretion was collected in a screen covered bucket which contained 30 m1 of 6 normal sulfuric acid. The total volume was measured daily and diluted to five liters with water. A one liter sample of the diluted urine from each of the seven days was saved until the end of the col- lection period when a subsample was taken from the pooled samples. Laboratory Analysis: Drymatter of the forage offered, the forage refused and the feces were determined by drying the samples at 110°C for 24 hours. Total nitrogen of all dry forage samples and dry feces was determined by the micro—Kjeldahl procedure after they had been pulverized by an electric blender. The same method was used to determine the total nitrogen of the urine samples. Statistical Analysis All data reported in this dissertaion were analyzed on an IBM 3600 computer at the Michigan State University Com- puter Laboratory. Analysis of variance procedures were used in all experiments, and Duncan's New Multiple Range Test was used to test for significant differences between means. IV. RESULTS AND DISCUSSION Expertment l — Steers Grazing Sorghum Pastutes firw Complete results of this experiment are shown in Tables 4 through 9. Only 146 of the 150 steers that were allotted to sorghum pastures finished the experiment (Table 4). One of the "Pro-Lix" steers broke his leg while being sprayed and had to be removed from the experiment on August 2. Three of the steers (2 control and 1 "Pro-Lix") died within a period of 8 days during the experiment (August 6, 7 and 13). The cause of death was not positively established, but anthrax was suspected. Subsequently, all experimental ani- mals were vaccinated for anthrax and no other death or ill- ness was observed in the steer groups. Supplement and Feed Intake: As shown in Table 5, the crude protein analysis of the sorghum was relatively constant from period to period. However, the forage appeared to be composed of primarily stalks and roots at the end of the trial. Since most of the digestible protein contained in sorghum is found in the leaf blades and grains (Quinby and Marion, 1966) it is probable that the digestible protein decreased as the trial progressed. As expected, the actual crude protein levels found in this severely weathered forage (4 a 4.6%) is substantially below the 8.3% requirement given by the National Research Council (1970). The deficiency of protein in weathered, winter forage is in agreement with 28 29 Eonm om>0EmH one unmflms psmfiflnmmxmlpflfi mGHH5© UmusnnH .xmucusm ompommmsm mango pmfio mm>amo Buom mnm>s .pmxno3 mcflmn maflns Gmxonn mmq .csocxcs sumac mo mmwmo .ucwfifiumoxm mo moflumcHEHmp ou Hofium ©m>amw msoo mmmnu mo spomu .mma smxoum .usmfiflnomxm .szosxss wmsmu .vwsno ssosxss mmsucmawnmoxm mcflnsw .mwsoEsmsm mo chap II mamo Hanan .mEoumfixm oxHHImcmnmu pmufibfiaxm .300 mcflumpomausoc m mm powwow“ was 300 on» umoH was mamo m HHS cm I I I I om omuOOHm mumwpm om I I I I om Houuaoo onwoonm< we OAH I ma I om xHAIOHm om I I I I om omIoonm mummum we I I .~ I om Houncoo esnmuom pm I I mm H om xHquum em I I ma m om omIooflm mm AH I :H m om HOHBQOO mm>Hmo mm HHH m I I om xHAIOHm mm ma v I I om OMIoon 300 mm I m I I om Houusou .oqusoz um I m I I om xflqlonm em I v «N I om omIoon em I m I I om Honucou Boo .omq ucmefinmoxm mGOmmmm moono usofifinmmxm .uB pmnflm usmEummHB unmepmmne Hmeflcm mcflnwflsflm stuo How Eoum no msfluso on moanm ou m0 mth Um>oEmm on powwow mcfiwa umoq mm>Hmu pmcmflmmd Insane .usmfiflnmmxm Eonm Hm>0Emm How mQOmmmm can usoEflHmoxm osflnmflcflm pan mcflunmum mHmend mo HmbEDZII.v mHQMB 30 lother work previously cited. Wallace and Denham (1970) and Harris gt gt. (1957) have reported that the nutritive value of representative samples of forage may be misleading because the diet of cattle on range may differ significantly from total herbage available. Cook gt gt. (1948) reported that a much higher quality for— age is consumed than chemical analysis of bulk samples would Table 5.--Crude Protein Levels Found in Representative Sam- ples of Experimental Pastures.* Initial Mid-Experiment Final Experiment Analysis Analysis Analysis Date of Samples June 30 August 14 October 2 1 (sorghum steers) 4.0 4.2 4.6 2 (Agropero steers) 5.1 4.0 4.5 3 (sorghum cows) 3.4 4.5 4.4 *All values are expressed on a 100% drymatter basis. indicate. In spite of these recognized limitations of rep- resentative forage samples, the extremely low protein con— tent of the forages (Table 5) does indicate a need for pro- tein supplementation especially if the forages are to be used for young cattle. After three weeks of gg libitum supplement feeding, the amount of "Pro-Lix" and "Rico-30" offered was limited so that the average daily intake per steer (Table 6) was 833.8 and 818.7 g for the "Rico-30" and "Pro-Lix" treatments, 31 .DsmEHHmwa Eonm ©m>oEmn mHmEHcm mmanosH .wmp mom 0 com pmadmsoo MHmo some @qHESmmd .mHmmeusmnmo CH ssozw mum mmmp MHmo mo Hmbfisz mfimnw mEMHmOHHM '40!me :Ammmmv II mv.hmh mmHv moms mm xHHIonm m :Amvwmv II ms.moa mmsm cams mm omIoon Amsoo enamHOmv m 0.4m m.mmm oosm come em xHquum Amnomnm oumdoummv N m.mn >.hHm ommm meme mm xHHIonm H 0.0m m.mmm woos cows om omIoon Amummum ssanOmV H coHuofismsoo aoHumESmsoo NaoHumEsm when .umxm no pnmEmHmmsm HsmEHHomxm mmEHcm HMHOB mmEHsd mHHmaucou Hmuoa meHsa mama .m nmsounp H mDQoEHummxm CH mHmEHCm mo coHumfistOU unmEmHmosmII.m mHnma 32 respectively. The daily supplement intake was below that originally planned and was a result of the approximate nature of the release of supplement from the storage tank to the feed pan of the supplement feeder. The "Pro—Lix" supplement is 5% higher in crude protein equivalent than "Rico-30" (35% versus 30%). Therefore, the actual crude protein equivalent provided per day was 286 g for "Pro-Lix" and 250 g for "Rico- 30". Weight Changes: The weight changes of the sorghum steers are shown in Table 7. The average initial weight was 240.6, 240.8 and 243.0 kg for the control, "Rico-30", and "Pro-Lix" steers, respectively. There was no significant difference in initial weight. The control steers lost an average of 3.3 kg during the first 49 days of the experiment while the "Rico-30" steers gained 4.2 kg and the "Pro—Lix" steers gained 2.7 kg. The difference between the "Pro-Lix" and "Rico-30" treatments were not significant, but both groups of supplemented steers performed significantly better than the control steers (P < 0.05). During the first period, 30 of the control steers lost weight while only 17 "Rico-30" steers and 18 "Pro-Lix" steers lost weight. During the second half of the experiment, the forage was much sparser, the weather was colder and all but 10 of the 146 steers grazing sorghum lost weight. Eight of the steers that did not lose weight were in the "Pro-Lix" treatment group and two were in the "Rico-30" treatment group. 33 Table 7.--Weight Changes of Steers on Sorghum Pasturel'2 Treatments Control Rico-30 Pro-Lix No. of Steers 48 50 48 Initial Wt. (6/26) 240.6 240.8 243.0 Mid—Expt. Wt. (8/14) 237.3arb 245.0a 245.6b Days on Test 49 49 49 Av. Gain Since Initial Wt. -3.3a'b 4.2a 2.7b No. of Steers Losing Wt. 30 17 18 Final Wt. (9/30) ’ 218.1a 231.9a 238.1a Days Since Last Wt. 47 47 47 Av. Gain Since Last Wt. -l9.2a -13.1a -7.5a No. of Steers Losing Wt. 48 48 40 Total Days on Test 96 96 96 Total Gain on Test -22.5a --8.9a --4.9a No. of Steers Losing Wt. 48 41 37 1All weights and gains are kilograms. 2Values with the same superscripts and in the same row are significantly different (P < 0.05). 34 The average weight losses during the last period were 19.2, 13.1 and 7.5 kg for the control, "Rico-30" and "Pro— Lix" groups respectively. All of the differences in final weights, weight losses during the second period and total weight losses were significant (P < 0.05). The control steers lost an average of 22.5 kg during the experiment while the "Rico-30" and "Pro—Lix" treatment lost an average of only 8.9 and 4.9 kg respectively. Table 8 shows the necessary cost of the supplements relative to the price of cattle to justify providing supple- ments. The cost of 5.9 kg of "Rico-30" would have to be less than the price of a kilogram of cattle to justify supplementing steers with "Rico-30" when they are wintered on sorghum pas- tures under conditions similar to this experiment. Simi- larly, the total cost of 4.5 kg of "Pro-Lix" would have to be less than the price of one kilogram of live beef to make "Pro—Lix" supplementation profitable. In other words, if cattle are selling for $0.25 per kg (a typical Argentine price) then "Rico—30" would have to sell for less than $0.042 per kg and "Pro-Lix" would have to sell for less than $0.056 per kg to be profitable. It should be emphasized that these figures pertain only when similar cattle are fed the same level of supplement and under similar conditions. This was a very atypical year in Argentina. There was an abundant rainfall during the early winter and this apparently helped the agropero pastures and lessened the value of the sorghum pastures. 35 In a typical year, steers grazed on sorghum perform much better than the sorghum steers in this experiment and steers grazed on agropero perform much worse than the agropero steers in this experiment (Haumfiller, 1969). In addition, it is probable that feeding supplements at different levels would give entirely different results. Table 8.—-Cost of Supplement Necessary to Make Supplementa- tion Profitable for Steers Wintered on Sorghum. Treatments Control Rico-30 Pro-Lix Av. Total Wt. Gain (Table 7) '22-5i *8-9 -4.9 Av. Wt. Advantage -- 13.6 17.6 Av. Supplement Consumption “ 80.0 78.5 (Table 6) Relative Value of Supplement2 " 5-9 4.5 1All weights are kilograms. 2Kilograms of supplement required to produce 1 kilogram wt. advantage over the controls. Plasma Carotene and Vitamin A Concentrations: The plasma carotene and vitamin A values of the steers on sorghum pas- ture are in general agreement with the ranges reported by Lexlesz (1939), Wheeler gt_gt, (1957), Beeson gt gt. (1961), Wellenreiter gt gt. (1969) and Ullrey gt gt. (1970). The average initial and midtexperiment vitamin A levels for the sorghum steers (Table 9) were above the concentrations 36 Table 9.——P1asma Caroteng gnd Vitamin A Concentrations of Sorghum Steers ' Treatments Control Rico-30 Pro-Lix No. of Steers Sampled 15 15 14 Date: June 26 Initial Plasma Carotene 316 309 363 Standard Error 28.4 28.4 28.4 Initial Plasma Vitamin A 29.2 27.0 32.4 Standard Error 3.8 3.8 3.8 Date: August 14 Mid—Expt. Plasma Carotene 215 161 185 Standard Error 16.5 16.5 16.5 Mid-Expt. Plasma Vitamin A 30.3a 32.8 39.0a Standard Error 2.3 2.3 2.3 Date: September 30 Final—Plasma Carotene 469 440 384 Standard Error 24.8 24.8 24.8 Final Plasma Vitamin A 14.4 12.4 15.4 Standard Error 1.8 1.8 1.8 1All carotene and vitamin A values are mcg/lOO m1 plasma. 2Values with the same superscript are significantly differ- ent (P < 0.05). 37 reported as adequate for normal health and growth by Moore (1939), Davis and Madsen (1941) and Kohlmer and Burroughs (1970). These workers reported the minimal adequate plasma vitamin A values as 20 to 25 mcg per 100 ml of blood plasma. The "Pro-Lix" treatment had a significantly higher (P < 0.05) plasma vitamin A concentration at the mid-experiment deter— mination, but there were no other significant differences among the treatments for measures of plasma vitamin A and carotene. The final plasma vitamin A levels were below the 20 to 25 mcg per 100 m1 plasma that was reported as normal, but no clinical symptoms of vitamin A deficiency were observed. Providing vitamin A in the supplement to the "Pro-Lix" and "Rico-30" treatments did not help to avoid a decrease in plasma vitamin A levels. These results are in agreement with work reported by Smith gt gt, (1964) who found that plasma vitamin A levels were not significantly affected by diet. Ullrey and co-workers (1970) found virtually no difference in plasma concentrations of vitamin A injected cows when compared with cows that received no vitamin A in- jections (24.2 and 24.4 mcg per 100 ml, respectively). In contrast, several experiments have demonstrated the depend— ence of plasma vitamin A and carotene concentrations on both previous stores and current intake (Davis and Madsen, 1941; Kuhlman and Gallup, 1942; Braun, 1945 and Pope gt gt., 1958).‘ Similar to the final plasma carotene concentrations 38 in this study, Ullrey gt gt. (1970) found high plasma caro- tene values (428 and 445 mcg per 100 ml) associated with low plasma vitamin A levels (19.6 and 20.9 mcg per 100 ml) at the time initial samples were taken. In all other work reviewed the ratio of carotene concentration to vitamin A concentration was much lower. The analysis used for caro- tene did not discriminate between the various carotenoids and the amount of vitamin A that they can be converted to. This is probably one of the factors responsible for the var- iability of carotene-vitamin A ratios found in blood plasma. There is disagreement in the literature concerning the effect of protein or nitrogen level in the ration on vita- min A and carotene metabolism. Rechcigl gt gt. (1962), Erwin gt gt. (1963) and Smith gt gt. (1964) reported that plasma vitamin A concentrations were depressed by high levels of protein or urea in the diet. In contrast, Gallup and associates (1950 and 1951) reported that the level of urea in the diet had no effect on carotene and vitamin A utilization. The failure of the supplemented groups to respond with higher plasma vitamin A concentrations may be due to an interaction with the nitrogen or nitrogen com- pounds in the diet. Experiment 2 - Steers Grazing Agropero (Agropirum elongatum) Pastures Complete results of the parameters measured of the two groups grazing agropero pastures are shown in Tables 4 39 through 6 and Tables 10 through 12. All 50 steers in both the control and "Pro—Lix" treatments completed the experi— ment (Table 4). Supplement and Feed Intake: As shown in Table 5 the crude protein levels of the agropero samples declined from 5.1% to 4.0% during the experiment. The agropero pastures were highly variable in the type of forage available. It is doubtful that the forage analyzed was truly representa- tive of the forage consumed. The herbage consisted primari- ly of dry, dead older growth and a green undergrowth. The steers exhibited a preference for the younger grass, but it was not possible to accurately sample the relative amount of the two types of forage consumed. This observation is supported by the results of Cook gt gt. (1948) who reported that sheep consumed a much higher quality forage than shown in the bulk samples that were analyzed. The final forage sample was collected just after grass started to turn green in the spring and this probably accounts for the increase in crude protein from 4.0% during the middle of the experiment to 4.5% crude protein in the drymatter of the forage at the end of the trial. The pro- tein level of all agropero samples analyzed was below the 7.8% requirement listed by the National Research Council 11970) . The "Pro-Lix" supplement was provided gg libitum to the agropero steers throughOut the experiment. The daily consumption of "Pro-Lix" per steer (562.5 g) was considerably 40 lower than the expected daily consumption of approximately 900 g (Table 6). This was especially true during the first two-thirds of the trial when the daily consumption of "Pro- Lix" per steer was only 500 g. The steers were consuming approximately 800 g per day when the experiment was termi— nated. Wetght Changes: The weight gains of the agropero steers are shown in Table 10. The average initial weight was 242.4 kg for the control and 236.7 kg for the "Pro-Lix" steers. The difference in initial weight was not significant. The weight gains were inconsistent as the control steers gained significantly (P < 0.05) more weight than the "Pro- Lix" steers during the first 49 days and the "Pro-Lix" steers gained significantly (P < 0.05) more than the control steers in the second half of the experiment. The total gain of the "Pro-Lix" steers (23.4 kg) was significantly (P < 0.05) higher than the total gain of the control steers (17.5 kg). The average mid-experiment weight of the control steers was significantly (P < 0.05) higher than the "Pro-Lix" steers. However, there was virtually no difference between the treat- ment groups for final weight. In contrast with the weight losses found with steers grazing sorghum only two of the steers grazing agropero lost weight during the experiment (Table 10). The pastures used for the agropero steers were changed at the time of the mid-experiment weight so that each group grazed each of the two pastures for one-half of the experiment. 41 ’2 Table lO.--Weight Changes of Steers on Agropero Pasture1 Treatments. Control Pro-Lix No. of Steers 50 50 Initial Wt. (6/26) 242.4 236.7 Mid-Expt. Wt. (8/14) 254.6a 241.5a Days on Test 49 49 Av. Gain Since Initial Wt. 12.3a 4.86 No. of Steers Losing Wt. 4 14 Final Wt. (9/30) 259.9 260.2 Days Since Last Wt. 47 47 Av. Gain Since Last Wt. 5.2a 18.7a No. of Steers Losing Wt. 11 0 Total Days of Test 96 96 Total Gain on Test 17.5a 23.5a No. of Steers Losing Wt. 2 0 1All weights and gains are kilograms. 2 . . . Values With the same superscripts and in the same row are significantly different (P < 0.05). 42 Therefore, part of the difference in performance of the treatment groups may have been a result of the pasture being grazed. The two agropero pastures used were adjacent and there were only minor observable differences between them. The agropero steers were infected with mange during the first 30 days of the experiment. All experimental ani- mals were sprayed twice at a 14 day interval for external parasites after detection of the mange infestation. The mange infestation appeared much more severe in the agropero steers than in any of the other experimental groups. The agropero steers receiving "Pro-Lix" supplement appeared to have a more severe infestation than the control steers. Brannon and associates (1954) reported that the feeding of molasses depressed the intake of herbage. It is doubt- ful that this finding explains the decreased gain of the "Pro-Lix" steers in the first half of the experiment since the supplemented steers outgained the controls during the last half of the trial. Further, several workers have reported that increasing the protein content of a low pro- tein diet increases the feed intake and weight gains (Ross gt gt., 1954; Bush gt gt., 1955; and Woods gt gt., 1956). Table 11 shows the necessary cost of "Pro-Lix" relative to the price of live beef to justify feeding "Pro-Lix" to steers grazing agropero pastures under the conditions of this experiment. The cost of 9 kg of "Pro—Lix" would have to be less than the price of 1 kg of live cattle to have been profitable in this experiment. Steers wintered on 43 agropero in Argentina usually lose weight (Haumfiller, 1969) so it is doubtful that the 9:1 ratio of supplement to beef is truly representative of the value of supplement over a number of years. Table ll.--Cost of Supplement Necessary to Make Supplement?- tion Profitable for Steers Wintered on Agropero Treatments Control Pro-Lix Av. Total Wt. Gain (Table 10) 17.5 23.5 Av. Weight Advantage over Control -- 6.0 Av. Supplement Consumption (Table 6) -- 54.0 Relative Value of Supplement2 -- 9.0 1A11 weights are kilograms. 2Kilograms of supplement required to produce 1 kilogram wt. advantage over the controls. Carotene and Vitamin A: The carotene and vitamin A concentrations of the blood plasma for the agropero steers are shown in Table 12. The final plasma vitamin A values were below the 20-25 mcg per 100 ml reported as minimal for normal health and growth by Moore (1939) and Davis and Madsen (1941). There were no clinical symptoms of vitamin A deficiency observed during the experiment. The final plasma vitamin A concentrations were similar for the sor- ghum and agropero steers in spite of the fact that the sor- ghum steers lost weight and the agropero steers gained weight. This observation indicates that vitamin A deficiency was not 44 Table 12.—-Plasma Carotene and Vitamin A Concentration of Agropero Steers ' Treatments Control Pro-Lix No. of Steers Sampled 15 15 Date: June 26 Initial Plasma Carotene 294 279 Standard Error 23.9 23.9 Initial Plasma Vitamin A 26.1 27.9 Standard Error 3.4 3.4 Date: August 14 Mid-Expt. Plasma Carotene 449a 329a Standard Error 26.9 26.9 Mid-Expt. Plasma Vitamin A 47.7 41.2 Standard Error 3.8 3.8 Date: September 30 Final Plasma Carotene 459a 320a Standard Error 22.5 22.5 Final Plasma Vitamin A 19.4 17.7 Standard Error 2.1 2.1 1All carotene and vitamin A values are mcg/lOO ml plasma. 2Values with the same superscript are significantly differ- ent (P < 0.05)- 45 the reason for the weight loss of the sorghum steers. The plasma vitamin A concentrations were much higher during the middle of the experiment than at either the ini- tial or final determinations. All steers were maintained on corn aftermath pastures for 60 days prior to the initi- ation of the experiment and the relatively low plasma vita- min A and carotene concentrations at the initiation of the experiment are probably a result of low carotene in the diet. The increased plasma vitamin A and carotene concentra- tions during the first half of the experiment for the agro- pero steers was probably due to an increased level of caro- tene in the forage. In contrast, the plasma carotene con- centrations in the sorghum steers decreased during the first half of the experiment (Table 9). The experimental design included plans for carotene determination of all forage samples. However, these plans had to be abandoned due to a lack of equipment and the fact that the stringent treatment required to bring any biological material back to the United States would have destroyed most of the caro- tene present. There was no significant difference between the two treatments in any of the vitamin A determinations. However, the control steers had a significantly higher (P < 0.05) plasma carotene concentration at both the mid-experiment and final analysis. This tendency was also observed in the sorghum steers. The control steers received all of their 46 vitamin A in the form of carotene from the forage consumed while the supplemented groups received Vitamin A in the form of vitamin A in the supplement. The increased dietary vitamin A levels of the supplemented steers may have resulted in a decreased absorption of carotene and there- fore explain the differences among treatment combinations in the plasma carotene concentrations. Experiment 3 - Cows and Calves Grazing Sorghum Pastures Results of this experiment are shown in Tables 4 - 6, 13, 14, and 16. This experiment was analyzed in 3 units: lactating cows, non-lactating cows and calves. All cows and calves receiving the same supplement were run together. Since the cows whose calves were never found were continued on the experiment as non-lactating cows, the number of cows completing the experiment was different than originally planned and varied among treatments (Table 4). There were 27, 24 and 27 lactating cows that completed the experiment for the control, "Rico-30" and “Pro-Lix" treatments, respec- tively. Similarly, 23 control and "Rico-30" and 22 "Pro- Lix" non-lactating cows completed the experiment. One of the non-lactating cows calved on September 3 and was not included in the analysis of weight gains. One of the "Pro- Lix“ non-lactating cows was injured on August 15 while being weighed and was removed from the experiment. In addition, two lactating cows receiving the "Rico-30" supplement died during the experiment. These cows exhibited tetany-like 47 staggers and weakness prior to death, but death occurred in both cases after the cows were down for over a week and they failed to respond to an intraveinous administration of calcium glutamate which contained magnesium. The cause of death was not definitely established. Both lactating cows died at the first of September and their calves were not removed from the experiment. The number of calves finishing the experiment is also shown in Table 4. Four calves died during the experiment and l calf had to be removed because of an injury. There were 26 control and "Rico-30" calves and 27 "Pro-Lix" calves that completed the experiment. Supplement and Feed Intake: It was impossible to ascertain the consumption of supplement by the different types of cattle since the lactating cows, their calves and the non-lactating cows on each treatment were maintained together. The total consumption of supplement (Table 6) was 3728 kg for the "Rico-30" group and 4136 kg for the "Pro-Lix" cattle. If each calf consumed approximately 200 of supplement daily then the daily consumption of each cow would have been approximately 705 g for the "Rico-30" cows and 787 g for the "Pro-Lix“ cows. The quantity of sorghum pastures remaining during the latter part of the experiment was extremely sparse and obviously insufficient to maintain the number of cattle carried on it. Table 5 shows the results of the crude protein analysis of the pasture samples. The initial 48 sample contained 3.4% crude protein in the drymatter and was slightly below the protein level found in the initial sorghum sample from the steer pastures. The mid—experiment and final crude protein analysis of the sorghum pastures was virtually the same for the cows and steers. The nutrient requirements for beef cattle (N.R.C., 1970) gives the crude protein requirement for lac- tating and dry cows as 9.2 and 5.9%, respectively. The crude protein level of the sorghum pastures were approxima- tely one—half the requirement for lactating cows and sub- stantially below the requirement for dry pregnant cows. Weight Changes of Non-Lactating Cows: The experimental weights and weight changes of the non-lactating cows are shown in Table 13. None of the differences among treatments for either weights or weight gains were significant. During the first half of the trial all but S cows gained weight. The average weight gain was 17.0, 23.3 and 22.5 kg for the control, "Rico-30" and "Pro-Lix" groups respectively. During the last 48 days of the experiment, 52 of 68 non-lactating cows lost weight. The average weight losses were 3.0, 9.0 and 6.2 kg for the control, "Rico-30" and "Pro-Lix" cows. The weight losses during the second half of the experiment did not obliterate weight gains in the previous period. The control, "Rico-30" and “Pro-Lix" cows had respective average total gains of 14.0, 14.3 and 16.2 kg. The large weight gains of the control cows during the first half of the experiment make it clear that 49 Table l3.--Weight Changes of Non-Lactating Cowslr2 Treatments Control Rico-30 Pro-Lix No. of Cows 23 23 22 Initial Wt. (7/1) 349.1 333.5 351.1 Mid-Expt. Wt. (8/15) 366.1 356.9 373.6 Days on Test 45 45 45 Av. Gain Since Initial Wt. 17.0 23.3 22.5 No. of Cows Losing Wt. 3 0 2 Final Wt. (lO/l) 363.1 347.9 367.4 Days Since Last Wt. 48 48 48 Av. Gain Since Last Wt. -3.0 -9.0 -6.2 No. of Cows Losing Wt. 14 21 17 Total Days on Test 93 93 93 Total Gain on Test . 14.0 14.3 16.2 No. of Cows Losing Wt. 4 4 3 1All weights and gains are kilograms. 2All values with the same superscripts and in the same row are significantly different (P < 0.05). 50 supplementation is not necessary for non—lactating cows grazing sorghum pastures when adequate forage is available. Weight Changes of Lactating Cows: Table 14 shows the weight changes of the lactating cows in this experiment. The control lactating cows had a significantly (P < 0.05) heavier initial, mid-experiment and final weight than the "Rico-30" cows. This difference was not a result of the treatment, but due to the method of assigning the cattle to groups. The weight loss of the "Pro-Lix" cows (21.2 kg) during the second half of the experiment was significantly (P < 0.05) greater than the loss of either the control (15.3 kg) or "Rico-30" cows (13.8 kg). The "Pro-Lix" cows lost less weight during the first half of the experiment than the other two groups. The primary reason for the difference in the performance of the "Pro-Lix" cows was an error made during the time the cows were removed from feed and water the night before weighing for the mid-experiment weight. The "Pro-Lix" cows were inadvertently left in a lot that had access to water. When this was discovered the following morning, the cows were immediately removed from water and weighed in the afternoon, but they were not held away from water as long as the other two groups. There were no significant differences among the treat- ment groups for total loss of weight during the experiment. The respective total weight losses of the control, "Rico-30" and "Pro-Lix" lactating cows were 24.1, 21.9 and 24.4 kg. The fact that protein supplements did not alter the weight 51 Table l4.--Weight Changes of Lactating Cowsli2 Treatments Control Rico-30 Pro-Lix No. of Cows 27 24 27 Initial Wt. <7/1) 355.1a 320.0a 336.7 Mid—Expt. Wt. (8/15) 346.3a 311.8a 333.5 Days on Test 45 45 45 Av. Gain Since Initial Wt. -8.9 -8.2 -3.3 No. of Cows Losing Wt. 21 17 16 Final Wt. (10/1) 331.0a 298.1a 312.3 Days Since Last Wt. 48 48 48 Av. Gain Since Last Wt. -15.3b -13.8a -21.2a'b No. of Cows Losing Wt. 26 22 26 Total Days on Test 93 93 93 Total Gain on Test -24.1 -21.9 -24.4 No. of Cows Losing Wt. 26 23 27 1All weights and gains are kilograms. 2All values with the same superscript in the same row are significantly different (P < 0.05). 52 losses of the lactating cows indicates that the primary limiting factor is either energy or a combination of energy and protein. Obviously, the sorghum pastures were inept at meeting the nutritional requirements for lactating cows. Weight Changes of Calves: The weight changes of the calves nursing the lactating cows are shown in Table 15. All calves gained weight throughout the experiment. Since there was an unequal ratio of male to female calves within the different treatments, the weight gains were analyzed both for all calves and for the bull and heifer calves separately. The average total gain during the experiment was 20.4 kg for the bull calves and 18.8 kg for the heifer calves. The difference in total gain among the treatments for the bull calves approached significance. When the gains of the bull and heifer calves were analyzed together the "Pro- Lix" calves gained significantly (P < 0.05) more weight than either the "Rico-30" or the control calves. The average total gain of the control, "Rico-30" and "Pro-Lix" calves was 17.7, 18.9 and 23.0 kg, respectively. Thus, the "Pro- Lix" calves had a 5.3 kg advantage over the controls while the "Rico-30" calves only had a 1.2 kg advantage. A weight differential of this magnitude is not great enough to pay for the supplement required for both cow and calf under these conditions if the calf weight gains are the only advantage accrued. It is possible that much of the advantage gained by 53 .Amo.o v m u mmmo nmsoH «Ho.o v m u mmmo Homosv pcmHmmMHc mHDGMOHMHcme mum mumHHomHmmsm mEmm ecu SpHs QESHoo mEMm map cH mman>N .mcmma Hmsuom mum ucmfiummnu comm Hops: mm>Hmo HHSb can HmmHmn .Hmpofi men cH Enou coHpomwmucH cm usocuHs mHmMHmcm mundom ummmH mo .mEmumoHHx mum mmsHm> HHAHH esp How cmmfi wee HHSmmH may mum Eump nonum mnu can mm>Hmo HHm How mammfi one e.H m.o m.o w.v H.v N.v mcmwz mo Honnm .pum om\a mH\a m\a unmet: no mete m.mH m.m o.OH n.Hm m.mm a.mh om mm>Hmo HmmHmB HHH h.om v.0H m.0H o.m0H m.Hm m.Hm me mo>Hmo HHDQ HH4 n.mH m.m H.0H m.mm N.nm H.hn on mm>Hmo HHd m.Hm m.0H m.HH m.om m.mn m.mm m mm>Hmo Hmemm H.vm m.HH bm.mH m.m0H m.mm «.mm Hm mm>Hmo HHsm b.Mo.mm m.OH m.OH p.mm m.om 0.05 mH mm>Hmo HoMHmm ¢.om m.OH em.m m.mm o.mm «.mn w wm>Hmo HHsm bm.mH m.m «H.0H H.mm m.em m.vh mm AHHmv omloon m.nH h.m >.n m.>m m.nm N.om o mm>Hmo Hmemm m.>H m.m bH.m o.HoH N.Hm H.mm om mm>Hmo HHsm m>.>H m.m 4m.> N.OOH H.mm ¢.Nm om AHHmV Honucou chU GHmw chw uanmz ucmHmz ucmHmz mHmEHcm ucmfiummue Hmboa ccooom pmuHm Hmch .HQWMIcHz HMHHHCH mo .02 N.Hmm>Hmu mo mmmcmcu ucmHszI.mH GHQMB 54 supplementing lactating cows would be in a decreased calving interval. Further, the results could be entirely different if lactating cows were given access to pastures with ample forage, forage of a different type or if just the calves were given access to the supplement. Carotene and Vitamin A of Cows: The results of the plasma carotene and vitamin A analysis of both the lactating and non-lactating cows are shown in Table 16. The plasma carotene and vitamin A values for the cows were analyzed by least squares. There did not appear to be any inter- action between the type of cow and the supplements used. None of the differences among treatments for either plasma carotene or plasma vitamin A concentrations were signifi- cant. Similar to both the steer experiments, the final plasma vitamin A concentrations were below the level listed as adequate for normal growth and health by Davis and Madsen (1941) and Kuhlman and Gallup (1942). In addition, these workers as well as Payne and Kingman (1947) reported that levels of vitamin A for optimum reproduction are sub- stantially higher and range from 78 to 150 mcg per 100 m1 of plasma. The initial carotene concentration of the non-lactating cows was significantly higher than for the lactating cows. However, all other carotene and vitamin A concentrations are virtually the same for lactating and non-lactating COWS . 55 . .Ine.o v my ucmHGMMHU >HucmoHMHcmHm mum cESHoo GEMm mcu CH mumHuomHmmcm GEMm mcu cuHB mmsHm>N .Hmcofi mcu cH Eumu coHuomumucH cm usocuHB mHmmHmcm mumsom ummmH wo uHSmmu mcu mum Eumu uouum mcu can magma ch .HE 00H\ moE mum mmsHm> HHHNH m.H e.em m.~ a.eH e.m a.em name: no nonnm .tnm o.Hm emm m.s~ see a.mm mHmm aH meuunuomq HH< m.Hm nee ~.am GNH m.am tees em maeutuoquaoz HH< H.HN eae a.mm mme p.mm Hem me neon Hum e.aH mes m.am amH m.am Gem eH xquonn a.mm nae m.em emu e.em mam eH omIoon a.Hm emm m.a~ oeH m.mm aem mH Honunoo c GHEmuH> mcmuouno c CHEwuH> mcmuoumo c cHEmuH> mcmuoumu mHmEHcfl ucmEummuB Henna emcee .uemetaz .unmetaz Hmauaau emanate no .02 N.Hm30U mo 4 cHEmuH> can wcmuounUII.wH chme 56 Experiments 4 and 5 - Nitrogen Balance Studies Feed and Supplement Analysis: Results of the analysis are shown in Table 17. The forages were harvested weekly by hand from the same pastures that were used for the exper- imental steers. The drymatter content was relatively con- stant for both forages until the final collection period when the percent drymatter dropped on both agropero and sorghum due to rain. The percent crude protein of the sor- ghum was relatively constant for all sorghum samples inclu- ding the feed that was refused. The crude protein levels found in the agropero samples were much more variable than that is the sorghum samples, but in all cases were below the requirements listed by the Nutrient Requirements of Beef Cattle (N.A.S., 1970). The agropero pasture had not been grazed for six months prior to the experiment and consisted of two types of growth: a greener, more palatable undergrowth and a dry, unpalatable older growth. The unconsumed portion of the agropero feed consisted almost entirely of the poorer qual- ity feed and ranged in protein from 2.36 to 2.51%. The agropero fed in the first trial was considerably higher in protein than in the following two trials and was primar- ily a result of a higher proportion of the green undergrowth in the feed. The percent crude protein in the two supple- ments were 36.5 and 29.2% for "Pro-Lix" and "Rico-30“ respectively. 57 Table l7.——Drymatter and Crude Protein Levels of Forage and Supplements Offered and Forage Not Consumed by Cattle on Nitrogen Balance Studies. Trial Type of Feed % D.M. % Crude Protein1 1 Sorghum 88.0 3.18 l Sorghum Refused 63.7 3.94 2 Sorghum 89.3 4.44 2 Sorghum Refused 81.3 4.04 3 Sorghum 69.3 4.40 3 Sorghum Refused 81.1 4.83 l AgrOpero 87.3 5.05 l Agropero Refused 69.3 2.51 2 Agropero 87.7 2.24 2 Agropero Refused 83.9 2.36 3 Agropero 78.9 3.35 3 Agropero Refused 87.7 2.40 All Pro-Lix Supplement 53.7 36.5 All Rico-30 Supplement 53.9 29.2 1Percent crude protein in the drymatter. 58 Drymatter Intake and Digestibility: As shown in Table 18, the drymatter consumption of the supplemented treatments for both agropero and sorghum forage was higher than the controls. The differences were significant (P < 0.05) for the agropero forage but not for the sorghum. There was no significant difference in drymatter intake between the "Rico- 30" and "Pro—Lix" supplemented treatments for either forage. These results disagree with Brannon gt gt. (1954) who re- ported that increasing the energy content of the ration resulted in a decrease in drymatter consumption. However, Ross gt_gt, (1954), Bush gt gt. (1955), Woods gt gt. (1956) and Raleigh and Wallace (1963) all reported similar increases in drymatter consumption of a low protein diet when the protein level was increased. There were no significant differences among any of the treatment groups for drymatter digestiblity. The drymatter digestibility ranged from 45.1 to 48.6% with an average of 46.3% for the sorghum steers. Similarly, the drymatter digestibility of the agropero fed steers ranged from 44.4 to 48.2% and averaged 45.8% Nitrogen Balance: The actual means of all nitrogen parameters measured are listed in Table 18. The differences in nitrogen intake among the different treatments (Table 18) were highly significant (P 5 0.01) for both the agro- pero and sorghum steers. The average daily nitrogen intake for the sorghum fed steers was 24.9, 64.4 and 75.7 g for the control, "Rico-30" and "Pro-Lix" steers respectively. 59 .Hmo.o v m u mmmo umBOH “3.0 v C u mmmo uneasy quHGMMHp wHquoHMHCmHm mum mmmuom meow ocu How UCm CECHOO mfimm wcu CH mumHHomummCm GEMm wcu cuH3 mmCHm>~ .pmumoHCCH mmHsumcuo mmmHCC map mom manna mum mmCHm> HHCH m.e a.me m a.mm a.me a.mH m.me «a.mm a.mH MMCH cmcuom Hmomm cmECm IHQ Inc 2Q Ixm so ICOU Iummue teaatnmm a Imm In: Ina Icoo an n so N.c%©5um OHHocmumz How mCmmz quEumoHB HmcuOCII.mH chme 60 Likewise, the agropero control, "Rico-30" and "Pro-Lix" treatments averaged 22.9, 61.2 and 68.4 g nitrogen con- sumed daily. "Pro-Lix" and "Rico—30" treatments on both forages had a significantly higher (P < 0.01) quantity of nitrogen absorbed daily than the control treatments. In addition, the "Pro-Lix" supplemented steers had a significantly (P < 0.05) greater amount of nitrogen absorbed per day than the "Rico—30" supplemented steers. The differences in absorbed nitrogen were reflections of the differences in nitrogen consumed. As expected, the treatment combinations that had higher nitrogen intakes resulted in higher losses of nitrogen in the urine. The increaSed urinary nitrogen excre— tion was a result of a 2 to 3-fold increase in both urine volume and the concentration of nitrogen in the urine. Although the fecal nitrogen excretion differed tremendously between forages, there were no significant differences among supplements for daily fecal nitrogen excretion. The average nitrogen retention for the non-supplemented control treatments was negative for both forages. All three of the sorghum steers and two of the agropero steers were in a negative nitrogen balance while not receiving supplement. The differences in nitrogen retention among the supplements on sorghum forage approach significance while the differences among the agropero treatments were non- significant. V ._ SUMMARY The value of providing liquid supplements to steers and cows grazing frosted winter pastures in Argentina was studied in three feeding trials and two nitrogen balance studies. Two types of pasture, Agropirum elongatum (agro- pero) and Leoti red (sorghum), and two supplements, "Pro- Lix" and "Rico—30", were used. The vitamin A status of the animals involved in the feeding trials was monitored by determining plasma carotene and vitamin A levels of a ran- domly selected group from each treatment combination. Almost all of the yearling steers grazing sorghum lost weight during the experiment. The average total loss of the control, "Rico—30" and "Pro-Lix" supplemented steers during the experiment was 22.5, 8.9 and 4.9 kg, respectively. All of the differences among treatments in total weight loss were significant (P < 0.05). In order for supplementation to be profitable for steers grazing sorghum pastures under the conditions of this experiment, the price of 5.9 kg of "Rico-30" or the price of 4.5 kg or "Pro-Lix" would have to be less than the price of 1 kg of live beef cattle. In contrast to the weight loss of the sorghum steers, the agropero steers gained weight during the experiment. The average total weight gain of the control and "Pro-Lix" steers was 17.5 and 23.5 kg respectively. The control steers actually outgained the supplemented steers during the first 61 62 half of the experiment but this advantage was more than offset by the significantly higher (P < 0.05) weight gains of the "Pro—Lix" steers during the last half of the experi- ment. Nine kilograms of the "Pro—Lix" supplement would have to sell for less than 1 kg of live beef to make supple-‘ mentation of steers on agropero pastures profitable under the conditions of this experiment. There was virtually no difference in the performance of the non—lactating and lactating cows regardless of whether they were supplemented or not. However, the calves nursing cows receiving "Pro—Lix" supplement gained significantly more weight (P < 0.05) than the calves in either the "Rico- 30" or control treatment groups. The average total gain of the control, "Rico-30" and "Pro-Lix" calves was 17.7, 18.9 and 23.0 kg, respectively. The 5.3 kg advantage of the "Pro-Lix" calves would not be sufficient to offset the cost of supplement consumed by both the dam and calf through- out the experiment. However, calf weight gains may not be the only advantage of supplementing lactating cows. _ The conditions of this experiment were rather atypical for Argentina. Normally steers grazed on sorghum out—perform steers grazed on agropero. The agropero pastures were extremely good because they had not been grazed for six months and there was unusual rain during the early winter. The quantity of forage available in the sorghum pastures was in- sufficient for the number of cattle grazed in them. This was especially true for cows grazing sorghum pastures. 63 There is considerable disagreement as to the value of plasma carotene and vitamin A levels for predicting the vitamin A status of cattle. The plasma values represent molecules which have been absorbed and are being transported to storage as well as molecules that have been mobilized from storage and are being transported to sites of conver— sion or use. I There were few differences among the different supple- ments for any of the analysis of plasma vitamin A levels. The final plasma vitamin A concentration of all treatment groups was below the level reported as adequate for normal health and growth by Davis and Madsen (1941) and Kuhlman and Gallup (1942). The plasma carotene concentration of the control agropero steers was significantly (P < 0.05) greater than that for the "Pro-Lix" steers on the same pas- ture. Although not significant, there was a trend for the plasma carotene concentration of the controls to exceed the carotene level of the supplemented animals in all experi- ments. The control animals received all of their vitamin A in the form of carotene from the forage consumed while the supplemented groups received vitamin A in the form of vitamin A in the supplement. The increased dietary vitamin A levels of the supplemented animals may have resulted in a decreased carotene absorption and therefore, explain the lower plasma carotene concentrations of the supplemented steers. The nitrogen balance of the control treatment was 64 negative for both the agropero and sorghum forages. The drymatter intake was greater for the supplemented steers on both forages, but only the differences on agropero were statistically significant (P < 0.05). There were no signi- ficant differences among any of the supplements for drymatter digestibility. The results of this experiment illustrate a great poten- tial for increasing beef production in Argentina. The year (1969) in which this experiment was conducted was unusually favorable for agropero pastures and the experiment should be replicated to eliminate the season variables. There apparently is no return for supplementing pregnant, non- lactating cows, but much incentive exists for further study on supplementation of lactating cows with calves and steers. It is quite possible that further study will illustrate how supplementation can be regulated to increase the response found in this study. BIBLIOGRAPHY BIBLIOGRAPHY Almquist, H. J. 1952. Relation of vitamin A intake to plasma and liver vitamin A content. Arch. Biochem. 39:243. Arias, C., W. Burroughs, P. Gerlaugh, and R. M. Bethka. 1951. The influence of different amounts and sources of energy upon in vitro urea utilization by rumen microorganisms. J. Animal Sci. 10:683. Baker, F. H., R. MacVicar and L. S. Pope. 1953. Placental and mammary transfer of vitamin A and carotene by beef cows. Proc. Soc. Exp. Biol. and Med. 83:571. Baker, F. H., L. S. Pope and R. MacVicar. 1954. The effect of vitamin A stores and carotene intake of beef cows on the vitamin A content of the liver and plasma of their calves. J. Animal Sci. 13:802. Bartlett, 8., and A. G. Cotton. 1938. Urea as a protein substitute in the diet of young cattle. J. Dairy Res. 9:263. Beeson, W. M., M. T. Mohler, and T. W. Perry. 1964a. Sup- plement A vs. Purdue 64 supplement and the effect of Co-Ral, Selenium and tylosin on the performance of steers. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept. Beeson, W. M. and T. W. Perry. 1964b. 1964 Purdue Protein supplements for beef cattle. Purdue agr. Exp. Sta. Cattle Feeders Day Rept. Beeson, W. M. and T. W. Perry. 1969. Effective utilization of urea by beef cattle. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept., AS-386, p. 6. Beeson, W. M. and T. W. Perry. 1970. Liquid feeding: His- tory - Problems - Research. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept., AS-391, p. 5. Beeson, W. M., T. W. Perry, C. F. Hatch, and M. T. Mohler. 1961. Nutritional factors affecting the utilization of dry and liquid high-urea supplements. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept., p. 35. Beeson, W. M., T. W. Perry, W. H. Smith and M. T. Mohler. 1961. Levels of supplemental vitamin A for fattening beef cattle. J. Animal Sci. 202925 (AbSt.) 65 66 Beeson, W. M., T. W. Perry, C. G. VanSlyke and M. T. Mohler. 1968. The value of dehydrated alfalfa products and distillers dried grains with solubles on the utiliza— tion of high-urea supplements for finishing beef cattle. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept. Belasco, I. J. 1954. New nitrogen feed compounds for rum- inants -- a laboratory evaluation. J. Animal Sci. 13: 601. Belasco, I. J. 1956. The role of carbohydrates in urea utilization, cellulose digestion and fatty acid forma- tion. J. Animal Sci. 15:496. Bell, M. C., W. D. Gallup and C. K. Whitehair. 1953. Value of urea nitrogen in rations containing different car- bohydrate feeds. J. Animal Sci. 12:787. Bhattacharga, A. N. and R. G. Warner. 1967. Rumen pH as a factor for controlling feed intake of ruminants. J. Dairy Sci. 50:1116. Bodansky, O. and B. Markardt. 1951. Effect of Reichstein's compound L acetate on plasma, liver and kidney Vitamin A. J. Biol. Chem. 190:83. Bowstead, J. E. and H. T. Freedon. ~l948. Feeding urea to dairy cows with special reference to the palatability of feed mixtures containing urea. Sci. Agr. 28:66. Brannon, W. F., J. T. Reid and J. I. Miller. 1954. The influence of certain factors upon the digestibility and intake of pasture herbage by beef steers. J. Animal Sci. 13:535. Braun, W. 1945. Studies on the carotenoid and Vitamin A levels in cattle. J. Nutr. 29:73. Briggs, H. M., W. D. Gallup, A. E. Darlow, D. F. Stephens, and C. Ninney. 1947. Urea as an extender of protein when fed to cattle. J. Animal Sci. 6:445. Brown, L. D., C. A. Lassiter, J. P. Everett and J. W. Rust. 1956. The utilization of urea nitrogen by young dairy calves. J. Animal Sci. 15:1125. Burroughs, W., P. Gerlaugh, B. H. Edgington and R. M. Bethke. 1949. Further observations of the effect of protein upon roughage digestion in cattle. J. Animal Sci. 67 Burroughs, W., J. Long, P. Gerlaugh and R. M. Bethke. 1950. Cellulose digestion by rumen micro-organisms as influenced by cereal grains and protein rich feeds commonly fed to cattle using an artificial rumen. J. Animal Sci. 9:523. Burroughs, W., F. H. McGuire and C. Cooper. 1969. Attempts to improve liquid and dry all-urea type cattle supple- ments with fish soluble additions. Iowa State Univ. A.S. Leaflet R118. Bush, L. F., J. P. Williams and F. B. Morrison. 1955. A study of the protein requirements of fattening feeder lambs. J. Animal Sci. 14:465. Campbell, C. M., L. B. Sherrod and S. M. Ishizaki. 1969. Effect of supplemental protein and energy levels on the utilization of kikuyu grass (Pennisetum clandesti- num). J. Animal Sci. 29:634. Carr, F. H. and E. A. Price. 1926. Colour reactions attri- buted to vitamin A. Biochem. J. 20:497. Chapman, H. L., Jr., R. L. Shirley, A. Z. Palmer, C. E. Haines, J. W. Carpenter and T. J. Cunha. 1964. Vitamins A and E in steer fattening rations on pasture. J. Animal Sci. 23:659. Cook, C. W., L. E. Harris and L. A. Stoddart. 1948. Mea- suring the nutritive content of a foraging sheep's diet under range conditions. J. Animal Sci. 7:170. Davis, R. E. and L. L. Madsen. 1941. Carotene and vitamin A in cattle blood plasma with observations on repro- ductive performance at restricted levels of carotene intake. J. Nutr. 21:135. ' Dinning, J. S., H. M. Briggs and W. D. Gallup. 1949. The value of urea in protein supplements for cattle and sheep. J. Animal Sci. 8:24. Erwin, E. S., R. S. Gordon and J. W. Algero. 1963. Effect of antioxidant, protein and energy on vitamin A and feed utilization in steers. J. Animal Sci. 22:341. Ewing, S. A. and W. Burroughs. 1963. Urea supplements in beef cow wintering rations. Iowa State Univ. A.S. Leaflet R56. Flora, C. C., R. E. Ward, S. I. Bechdel, N. B. Guerrant and R. A. Dutcher. 1939. Carotene in the nutrition of dairy calves. J. Dairy Sci. 22:321. 68 Frey, P., R. Jensen and W. E. Connell. 1947. Vitamin A intake in cattle in relation to hepatic stores and blood levels. J. Nutr. 34:421. Gallup, W. D. and H. M. Briggs. 1948. The apparent diges- tibility of prairie hay of variable protein content, with some observations of fecal nitrogen excretion by steers in relationship to their dry matter intake. J. Animal Sci. 7:110. Gallup, W. D., H. M. Briggs, L. S. Pope and J. Tucker. 1950. Possible effect of urea and source of protein supple- A ment on vitamin A utilization by sheep. J. Animal Sci. 9:656 (Abst.) Gallup, W. D., H. M. Briggs, L. S. Pope and J. Tucker. 1951. Comparative effect on vitamin A metabolism in sheep of I urea, soybean oil meal, and cottonseed meal as sources of protein. .J. Animal Sci. 10:252. Gallup, W. D., C. K. Whitehair and M. C. Bell. 1954. Utilization of urea and protein nitrogen by ruminants fed high-molasses and sugar rations. J. Animal Sci. 13:594. Gay, N. and R. L. Vetter. 1967. A comparison of liquid and meal type supplements for feedlot cattle. Iowa State Univ. A.S. Leaflet R96. Guilbert, H. R. and G. H. Hart. 1935. Minimum vitamin A requirements with particular reference to cattle. J. Nutr. 10:409. Hamilton, T. S., W. B. Robinson and B. C. Johnson. 1948. Further comparisons of the utilization of nitrogen with that of some feed proteins by sheep. J. Animal Sci. 7:26. Harris, L. E., J. C. James and C. W. Cook. 1957. A method of feeding supplements to individual cattle on winter range. J. Animal Sci. 16:872. Harris, L. E. and H. H. Mitchell. 1941. The value of urea in the synthesis of protein in the paunch of the rumi- nant. II. In growth. J. Nutr. 22:183. Harris, L. E., S. H. Work and L. A. Henke. 1943. The utilization of urea and soybean oil meal nitrogen by steers. J. Animal Sci. 2:328. 69 Hart, E. B., G. Bohstedt, H. J. Deobald and M. I. Wegner. 1939. The utilization of simple nitrogenous compounds such as urea and ammonium carbonate by growing calves. J. Dairy Sci. 22:785. Haumfiller, R. 1969. Personal communication. Campo Vet. Rosario, Argentina. Henderson, H. E. and M. R. Geasler. 1970.. Urea treated corn silage full fed with varying levels of protein, sources of protein and concentrate levels. Rept. of Beef Cattle Research, Michigan State University, p. 25. Henderson, H. E., H. W. Newland and W. K. Brown. 1960. Simple and complex protein supplements for fattening steer calves. 37th Annual Cattle Feeders Day Rept., Michigan State University, p. 8. Henderson, H. E. and B. Purser. 1968a. Urea additions to corn silage. Michigan State University Beef Cattle Day Rept., p. 29. Henderson, H. E., and B. Purser. 1968b. Effect of type of silo and urea addition on feeding value of late har- vested corn silage. Michigan State University Beef Cattle Day Rept., p. 39. Hobbs, C. S., W. D. Gallup and R. B. Taylor. 1945. The composition and apparent digestibility of bluestem grass in the growing stage and in the dry and hay stages when supplemented with cottonseed cake. J. Animal Sci. 4:395. Hodgson, R. E., S. R. Hall, W. J. Sweetman and H. T. Converse. 1964. The effect of vitamin A deficiency on reproduc- tion in dairy bulls. J. Dairy Sci. 29:669. Hoefer, J. A. and W. D. Gallup. 1947. The comparative value of carotene concentrate, alfalfa meal and fish liver oil in maintaining the vitamin A content of the blood and liver of fattening lambs. J. Animal Sci. 6:325. Johnson, B. C., T. S. Hamilton, H. H. Mitchell and W. B. Robinson. 1942. The relative efficiency of urea as a protein substitute in the ration of ruminants. J. Animal Sci. 1:236. Kercher, C. J. and L. Paules. 1967. Liquid vs. dry pro- tein supplements for fattening yearling steers. J. Animal 801. 263921 (Abst.) 7O Kohlmer, R. H. and W. Burroughs. 1970. Estimation of cri- tical plasma and liver vitamin A levels in feedlot cattle with observations upon influences of body stores and daily dietary requirements. J. Animal Sci. 30:1012. Kuhlman, A. H. and W. D. Gallup. 1942. The relation of carotene intake to blood carotene values of dairy cat— tle. J. Animal Sci. 1:68. Lelesz, E. 1939. Investigations of the vitamin content of blood. Estimation of vitamin A in the blood of live- stock. Acta. Vitaminologiae. 5:42. Lofgreen, G. P. 1965. Net energy of fat and molasses for beef heifers with observations on the method for net energy determination. J. Animal Sci. 24:480. Lofgreen, G. P. and K. K. Otagaki. 1960. The net energy of blackstrap molasses for fattening steers as determined by comparative slaughter techniques. J. Animal Sci. 19:392. Ludwig, C., S. A. Ewing, L. S. Pope and D. F. Stephens. 1967. The cumulative influence of level of wintering on the lifetime performance of beef females through seven calf crops. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 58. Martin, T. G., W. M. Beeson, M. T. Mohler and T. W. Perry. 1968. High-urea vs. natural protein supplements for finishing bulls. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept. McNaught, M. L. and J. A. B. Smith. 1947. The role of the microflora of the alimentary tract of herbivora with special reference to ruminants. 4. nitrogen meta- bolism in the rumen. Nutr. Abstr. and Rev. 17:18. Menzies, C. W., D. Richardson, F. H. Baker and R. F. Cox. 1955. Phosphoric acid as a source of phosphorus for ruminants. J. Animal Sci. 14:1217 (Abst.) Meyer, J. H., J. L. Hull, W. H. Weifkamp and S. Bonilla. 1965. Compensatory growth responses of fattening steers following various low energy intake regimes on hay or irrigated pasture. J. Animal Sci. 24:29. Miller, J. A., A. B. Nelson and G. R. Waller. 1958. Pro- tein supplements for wintering fall calving cows. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 102. 71 Mills, R. C., A. N. Booth, G. Bohstedt and E. B. Hart. 1942. The utilization of urea by ruminants as influ— enced by the presence of starch in the ration. J. Dairy Sci. 27:571. Mills, R. C., C. C. Lardinois, I. W. Rupel and E. B. Hart. 1944. Utilization of urea and growth of heifer calves with corn molasses or cane molasses as the only readily available carbohydrate in the ration. J. Dairy Sci. 27:571. Moore, L. A. 1939. Carotene intake, level of blood plasma carotene, and the development of papillary edema and nyotalopia in calves. J. Dairy Sci. 22:803. Myers, G. 8., Jr., H. O. Eaton and J. E. Rousseau, Jr. 1959. Relative value of carotene from alfalfa and vit- amin A from a dry carrier fed to lambs and pigs. J. Animal Sci. 18:288. National Research Council. 1970. Nutrient Requirements of Beef Cattle. Fourth revised edition, National Academy of Sciences, Washington, D. C. Nelson, A. B., R. D. Furr and G. R. Waller. 1962. Level of wintering fall calving beef cows. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 71. Nelson, A. B., L. R. Kuhlman, G. R. Waller and W. D. Camp- bell. 1961. Urea in protein supplements for wintering steer calves grazing native grass. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 76. Newland, H. W., H. E. Henderson, W. T. Magee, R. J. Deans, L. J. Bratzler, A. L. Pearson, R. W. Luecke and R. H. Nelson. 1961. Urea and energy levels, lysine supple- mentation and hormones for fattening steer calves. Michigan Cattle Feeders Day Rept., A.H. 67. Owen, E. C. 1951. Reviews of the progress of dairy science. II. Physiology and biochemistry of rumination. J. Dairy Res. 18:113. Payne, M. G. and H. E. Kingman. 1947. Carotene blood levels and reproductive performance in range Hereford cattle. J. Animal Sci. 6:50. Perry, T. W. and W. M. Beeson. 1968. Liquid non-protein nitrogen supplements for beef cattle. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept., RPR-379. 72 Perry, T. W., W. M. Beeson, M. T. Mohler, and W. H. Smith. 1962. Levels of supplemental vitamin A with and with— out sun cured alfalfa meal for fattening steer calves. J. Animal Sci. 21:333. Perry, T. W., W. M. Beeson, D. M. Robinson and M. T. Mohler. 1967. Liquid vs. dry supplements for fattening steers. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept., RPR-303. Perry, T. W., R. C. Peterson and W. M. Beeson. 1969. The value of supplemental distillers solubles, fish solu- bles, or alfalfa solubles in liquid supplements for fattening beef cattle. Purdue Agr. Exp. Sta. Cattle Feeders Day Rept., p. 29. Pinney, D. 0., L. S. Pope, C. V. Cotthem and K. Urban. 1962a. Effect of winter plane of nutrition on the performance of three- and four-year—old beef cows. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 50. Pinney, D. O., L. S. Pope, L. E. Malkus and D. Stephens. 1962b. Feedlot performance and carcass composition of slaughter cattle as affected by winter feed level of their dams. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 25. Pinney, D. O., L. S. Pope, D. Stephens and L. M. Henderson. 1962c. Lifetime performance of beef cows wintered each year on three different levels. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 63. Pope, L. S., J. L. Pitts and G. Waller. 1958. Effect of three levels of carotene intake during lactation on the performance of beef cows and their calves. Okla. Agr. Exp. Sta. Feeders Day Rept., p. 42. Quinby, J. R. and P. T. Marion. 1966. Sorghum for Forage. Forages. Edited by H. D. Hughes, M. E. Heath and D. S. Metcalfe. The Iowa State University Press. p. 346. Raleigh, R. J. and J. D. Wallace. 1963. Effect of urea at different nitrogen levels on digestibility and on per- formance of growing steers fed low quality flood mea- dow roughage. J. Animal Sci. 22:330. Ralston, A. T. and I. A. Dyer. 1959. Relationship of liver and plasma carotenoid and vitamin A content in cattle as affected by location and season. J. Animal Sci. 1838749 Rechcigl, M., Jr., S. Berger, J. K. Loosli and H. H. Williams. 1962. Dietary protein and utilization of vitamin A. J. Nutrition 76:435. 73 Reid, J. T. 1953. Urea as a protein replacement for rumi— nants: A reView. J. Dairy Sci. 36:955. Riggs, J. K. 1940. The length of time required for deple- tion of vitamin A reserves in range cattle. J. Nutri- tion 20:491. Riggs, J. K., R. W. Colby and L. V. Sells. 1953. The effect of self—feeding salt—cottonseed meal mixtures to beef cows. J. Animal Sci. 12:379. Ross, C. V., U. S. Garrigus, T. S. Hamilton and E. B. Earley. 1954. Comparing high—, medium-high-, and low-protein corn for fattening lambs. J. Animal Sci. 13:433. Rousseau, J. E., Jr., R. Teichman, H. D. Eaton, M. Dicks, K. L. Dolge, C. F. Helmboldt and E. L. Jungherr. 1958. Effect of initial vitamin A status on subsequent response of Holstein calves to carotene intake from artificial dehydrated alfalfa. J. Dairy Sci. 41:514. Rupel, I. W., G. Gohstedt, and E. B. Hart. 1943. The com— parative value of urea and linseed meal for milk pro- duction. J. Dairy Sci. 26:647. Smith, G. S., S. B. Love, W. M. Durdle, E. E. Hatfield, U. S. Garrigus and A. L. Neumann. 1964. Influence of urea upon vitamin A nutrition of ruminants. J. Animal Sci. 23:47. Smith, G. S., A. L. Neumann, W. G. Huber, A. H. Jordan and O. B. Ross. 1961. Avitaminosis in cattle fed silage rations supplemented with vitamin A. J. Animal Sci. 20:952. (Abst.) Speth, C. F., V. R. Bohman, H. Melendy and M. A. Wade. 1962. Effect of dietary supplements on cows on a semi-dessert range. J. Animal Sci. 21:444. Sutton, T. S., W. E. Krauss and S. L. Hansard. 1940. The effect of vitamin A deficiency on the young male bovine. J. Dairy Sci. 23:574. Swift, R. W., E. J. Thacker, A. Black, J. W. Bratzler and W. H. James. 1947. Digestibility of rations for rum- inants as affected by proportions of nutrients. J. Animal Sci. 6:432. Tillman, A. D. 1962. Mineralnvitamin interrelationship in ruminant nutrition. Okla. Agr. Exp. Sta. Livestock Feeders Day Rept. 74 Tillman, A. D., D. B. Singletary, J. F. Kidwell and C. I. Bray. 1951. ‘Methods of feeding cane molasses and urea to beef cattle. J. Animal Sci. 10:939. Ullrey, D. E., R. L. Covert, R. H. Wellenreiter, T. R. Greathouse and W. T. Magee. 1970. Vitamin A injections for wintering beef cows. Report of Beef Cattle Forage Research 1970. Michigan State Univ., p. 38. Wallace, J. D. and A. H. Denham. 1970. Digestion of range forage by sheep collected by es0phageal fistulated cat- tle. J. Animal Sci. 30:605. Wallace, J. D., K. L. Knox and D. N. Hyder. 1970. Energy and nitrogen value of sandhill range forage selected by cattle. J. Animal Sci. 31:398. Watkins, W. E., J. H. Knox and J. W. Benner. 1950. Caro- tene and vitamin A in the blood plasma of range cows. New Mex. Agr. Exp. Sta. Bul. 335. Weichenthal, B. A., L. B. Embry, R. J. Emerick and F. W. Whetzal. 1963. Influence of sodium nitrate, vitamin A and protein level on feedlot performance and vitamin A status of fattening cattle. J. Animal Sci. 22:979. Weir, W. C. and R. F. Miller, Jr. 1953. The use of salt as a regulator of protein supplement intake by breeding ewes. J. Animal Sci. 12:219. Weir, W. C. and D. T. Torrell. 1953. Salt-cottonseed meal mixture as a supplement for breeding ewes on the range. J. Animal Sci. 12:353. Wellenreiter, R. H., D. E. Ullrey, T. R. Greathouse, W. T. Magee and B. L. Schoepke. 1969. Vitamin A status of wintering beef cows. Report of Beef Cattle Forage Research 1969. Michigan State Univ., p. 30. Wheeler, R. R., P. H. Weswig, W. F. Brannon, F. E. Hubbert, Jr., and W. A. Sawyer. 1957. The carotene content of plasma and liver of range Hereford cows and their calves in the Northern Great Basin. J. Animal Sci. 16:525. Willett, E. L., L. A. Henke and C. Marugame. 1946. The use of urea in rations for dairy cows under Hawaiian condi- tions. J. Dairy Sci. 29:629. Williams, D. L., J. V. Whiteman, R. S. Pittman and A. D. Tillman. 1968. A comparison of cottonseed meal and urea in low protein winter range supplements for cattle. Okla. Agr. Exp. Sta. Misc. publ. No. 80, p. 10. 75 Woods, W} R., C. M. Thompson and R. B. Grainger. 1956. The effect of varying levels of protein and cerelose on the utilization of mature timothy hay by sheep. J. Animal Sci. 15:1141. IIIIIIIIIIIIII|||IIIIIIIIIIIIIIIII||IIIII|I|IIIIIIIIIIIIIIIIII 31293 03037 9535