‘4 I F609 mssaee an: mum ,. we: RlNG-NECKED PHEAgAwI “mm §oe Hue Dunc oi pk. D. kiECHEGMé STATE UNIVERSE“ Gary E. Duke 19267 LIBRARY Michigan Stave University This is to certify that the thesis entitled CHROMIUM-Sl IN METABOLIZABILITY AND FOOD PASSAGE RATE STUDIES WITH THE RING-NECKED PHEASANT presented by Gary Earl Duke has been accepted towards fulfillment of the requirements for Ph.D. degree in Fisheries and Wildlife // / , 7 , _ ./ ; I (7/5611! {/ -¢;; 2 C 54:4 .5/ Major professor 0-169 ABSTRACT CHROMIUM-Sl IN METABOLIZABILITY AND FOOD PASSAGE RATE STUDIES WITH THE RING-NECKED PHEASANT by Gary E. Duke Two techniques using chromium-51 were developed. In the first, a single-dose of chromium—labeled food was fed to test birds and the passage rates of the food were determined as the times of the first and last appearance of the label. In the second technique a continuous-dose of uniformly labeled food was fed to test birds for one to several days. The ratio of the concentration of Cr—Sl in the food to its concentration in the excreta permitted the ready computation of metabolizability coefficients. The weights of materials ingested and defecated also allowed computation of these coefficients by the total collection method. The two tech- niques were run in succession and passage rates, metaboliz- ability coefficients, and ingestion rates were determined and compared between cocks, between cocks and hens, between adults and chicks, and for three different diets. However, for an unknown reason, the coefficients as determined by the two methods, did not agree. The metabolizability coeffi— cient of a standard commercial diet averaged 63.49 percent Gary E. Duke by the total collection method and 53.68 percent by the ratio method for cocks in a controlled environment. The average minimum passage rate of the standard diet for cocks was 0.6 to 1.6 hours while the average max- imum passage time for materials not receiving cecal diges- tion was nine hours and for materials receiving cecal influ— ence the maximum rate was 38 hours. Cecal excreta are recognizable from rectal excreta and the concentration of isotope in cecal excreta over that in rectal excreta per— mitted a determination of the extent of cecal digestion. The standard diet provided an average of 3,073 calories of metabolizable energy per gram to the pheasant cocks tested, and an average of 1.8813 grams was eaten per hour. Similar information was obtained for pheasant hens, for chicks of various ages, and for cocks eating whole corn or chokeber— ries. The results of feeding trials using chromium-51 showed as much variance within the same male as between males. Metabolizabilities and maximum passage rates were slightly greater for hens than for cocks. Passage rates were faster for chicks up to 42 days of age than for adults, and the level of metabolizability of the standard diet was approximately 5 percent higher for chicks. The metaboliz- ability of corn was higher and of chokeberries lower than that of the standard diet. The passage rates of chokeber- ries and the standard diet were both shorter than the Gary E. Duke passage rate of corn. Considering both metabolizability and passage rate, the standard diet provided a higher average metabolizable energy per day than the other diets. Metab- olizability coefficients obtained with cocks on the standard diet by the ratio method were more variable than those obtained by the total collection method. Thus, the ratio technique employing chromium-51 is not considered valid for metabolizability determinations with pheasants. However, the ratio technique is of value in comparing relative day- time to nighttime digestibility and cecal to intestinal digestion. And, passage rate studies using chromium-51 are very useful. CHROMIUM-Sl IN METABOLIZABILITY AND FOOD PASSAGE RATE STUDIES WITH THE RING-NECKED PHEASANT BY Gary E. Duke A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Fisheries and Wildlife 1967 ACKNOWLEDGMENTS This study was supported by U. S. Atomic Energy Commission contract No. AT(ll-l)-1534. I wish to eXpress my appreciation to Dr. George A. Petrides, Department of Fisheries and‘Wildlife, whose pilot studies on the values of Cr-Sl as a food label led to my study. His advice during the project and his careful edit- ing of the manuscript are gratefully acknowledged. The advice of Dr. Robert K. Ringer of the Poultry Science Department was invaluable. I greatly appreciate his assistance in planning and methods and in physiological interpretation of results. Other members of the Poultry Science Department offered advice and laboratory space in which initial studies were accomplished. Dr. Leslie W. Gysel of the Fisheries and Wildlife Department and Dr. George J. Wallace of the Zoology Depart- ment furnished encouragement throughout the research and critical editing of the final manuscript. Frequent discussions with William W. Mautz, a fellow graduate student, were extremely helpful throughout the study and during preparation of the manuscript. My wife, Maryann, deserves much credit for her con- stant encouragement. ii TABLE OF CONTENTS Page INTRODUCTION . . . . . . . . . . . . . . . . . . . . . 1 METHODS . . . . . . . . . . . . . . . . . . . . . . . 7 Materials and Equipment . . . . . . . . . . . . . 7 Suitable Techniques in Developmental Trials . . . ll Single-Dose Technique . . . . . . . . . . . . ll Continuous-Dose Technique . . . . . . . . . . 14 The Ultimate Combination Technique in Comparative Trials . . . . . . . . . . . . . . . 19 RESULTS . . . . . . . . . . . . . . . . . . . . . . . 21 Results of Single-Dose Developmental Trials . . . 21 Results of Continuous-Dose Developmental Trials . . . . . . . . . . . . . . . . . . . . 28 Results of Comparative Trials Using the Combination Technique . . . . . . . . . . . . . 34 Additional Results . . . . . . . . . . . . . . . . 46 Feeding Trials with Chicks . . . . . . . . . . 46 Cecal Influence on a Diet . . . . . . . . . 51 Caloric and Moisture Content of Feeds and Excreta . . . . . . . . . . . . . . . . 55 Passage Rate of the Cr-Sl . . . . . . . . . . 55 Daily Cycles of Ingestion, Digestion, and Excretion . . . . . . . . . . . . . . . 57 Autopsy Findings . . . . . . . . . . . . . . . 60 Energy Budget . . . . . . . . . . . . . . . . 65 CONCLUSION . . . . . . . . . . . . . . . . . . . . . . 66 Evaluation of Cr—51 Used in the Ratio Method with Pheasants . . . . . . . . . . . . . 66 LITERATURE CITED . . . . . . . . . . . . . . . . . . . 68 iii Table 1. LIST OF TABLES Counts per grafi'of excreta from continuous- dose feeding trials with pheasants fed Turkey Breeder Pellets, Michigan State University, 1966 and 1967 . . . . . . . . . . . . . . . . . Data of experiment 4b from which Figure 1 was derived, Michigan State University, 1966 and 1967 O O O O O O O I O O O O O O O O O O O O O Digestibility information gained from Cr-51 feeding trials performed during the develop— ment of the single-dose technique with pheasants fed Turkey Breeder Pellets, Michigan State University, 1966 and 1967 . . . Digestibility information gained from Cr—51 feeding trials performed during the develop- ment of the continuous-dose technique with pheasants fed increasing doses of Cr-Sl with Turkey Breeder Pellets, Michigan State University, 1966 and 1967 . . . . . . . . . . . Digestibility information gained from Cr51 feeding trials using the combination technique, three separate diets, and male and female pheasants, Michigan State University, 1966 and 1967 . . . . . . . . . . . . . . . . . . . Digestibility and body weight information from Cr-51 single-dose feeding trials with pheasant chicks fed two diets, Michigan State University, 1966 and 1967 . . . . . . . . Degree of cecal influence for adult ring- necked pheasants on various diets, Michigan State University, 1966 and 1967 . . . . . . . . Calories per gram and percentage moisture of feeds and excreta from both juvenile and adult pheasants, Michigan State University, 1966 and 1967 . . . . . . . . . . . . . . . . . iv Page 18 22 27 33 37 48 53 56 Table 10. 11. Page Defecation rates for pheasant F—I during seven feeding trials in the controlled environment room on the standard diet, Michigan State University, 1966 and 1967 . . . 59 Cpm per gram of digesta from various segments of the pheasant GI tract after ingestion of a continuous-dose of Cr-Sl as determined by autopsy, Michigan State University, 1966 and 1967 . . . . . . . . . . . 62 Distribution of Cr-51 in the tracts of six female chickens on a Turkey Breeder Pellet diet. Samples were taken at intervals following ingestion of a single—dose of Cr—51 fed at about 12:45 a.m., Michigan State University, 1966 and 1967 . . . . . . . . 63 Figure 1. LIST OF FIGURES Defecation rate and pattern for a ring- necked pheasant after ingestion of a single-dose of Cr-51 on a Turkey Breeder Pellet. Michigan State University. Experiment 4b, 1966 and 1967. . . . . . . . Relationship of minimum and maximum passage time to the size of the Cr-Sl dose ingested by a pheasant. Michigan State University. 1966 and 1967 . . . . . . . . . . . . . . . Defecation rate and pattern for a ring- necked pheasant after ingestion of a continuous-dose of Cr-51 on Turkey Breeder Pellets. Michigan State University. Experiment 8d, 1966 and 1967 . . . . . . . Defecation rate and pattern for a ring- necked pheasant during a combination technique feeding trial in which both single and continuous-doses of Cr-51 were fed on Turkey Breeder Pellets. Michigan State University. Experiment 11a, 1966 and 1967 . . . . . . . . . . . . . . . . . vi Page 24 3O 32 36 INTRODUCTION Measurements of passage rate and digestibility of foods are basic to the study of bioenergetics. Livestock and poultry researchers have accomplished many investiga- tions of these phenomena, and although eXperimental ap- proaches have varied, most recent workers apply insoluble labels to the foods to be studied. The passage rate of food is the time required for a given quantity of that food to pass completely through the digestive tract. The proportion of a diet that is digested and absorbed determines the digestibility of that diet. The ratio of the concentration of a label in food to its concentration in feces from that food, subtracted from unity, gives the digestibility coeffi- cient of that food by the ratio method. The present study involves the ring-necked pheasant (Phasianus colchicus) as an eXperimental species and a deter- mination of the usefulness of chromium-51 (Cr-51) as a food label. The pheasant has apparently not been tested in this sort of experiment, and the value of Cr-Sl as a label has received only limited study. Many labels have been tested as indicator substances. Hoelzel (1930) tried rubber, cotton thread, seeds, beads, aluminum, silver, gold, and steel as food markers. Other labels include those found naturally in plants such as chromOgen (Reid §t_al., 1952) and lignon (Forbes and Garrigus, 1948). In addition, celluloid particles (Mueller, 1956), iron oxide (Bergeim, 1926; Tuckey g£_§1., 1958), ruthenium-106 (Hollis and Thompson, 1958), barium sulfate (Henry g£_a1., 1933), radioactive barium (Imabayashi g£;al., 1956), oats (Browne, 1922), chromium-51 (Petrides, 1964; Mautz and Petrides, 1967) have been employed. But the most widely used marker is chromic oxide which was first suggested by Edin (1918) for use in digestion trials. It is usually mixed directly with feeds but it is also available in paper pellets or shreds (Corbett gt_al., 1960; Border gt_§1., 1963; Troelson, 1963) which can be mixed with feeds. Chromic oxide has been used in nutritional studies of pigs (Schurch §E_al., 1952; Moore, 1957) man (Krenla, 1947; Irwin and Crampton, 1951), sheep (Elam §£_31., 1962; Johnson §£_al., 1964), cattle (Kane §E_§1., 1950; Smith and Reid, 1955), coturnix quail (McFarland and Freedland, 1965), and poultry (Olsson and Kihlen, 1948; Dansky and Hill, 1952; Hill and Anderson, 1958; Edwards and Gillis, 1959; and, Hill and Renner, 1963). Brandt and Thacker (1958) used Cr-51 to study COprophagy in rabbits. In addition to these chromic oxide studies, Odum (1961) studied excretion rates in two species of terrestrial insects and in a marine isopod using zinc-65. Hoelzel (1930) studied food passage rates in the rabbit, guinea pig, dog, cat, rat, mouse, monkey, adult female chicken, pigeon, and in himself. Malone (1965) determined the passage rate of certain plankton through mallard ducks while studying the effects of digestion on the plankton. Petrides (1964) determined passage rate and other digestive phenomena in the oppossum (Didelphis virginiana), bobcat (Lynx rufus), cotton rat (Sigmodon hispidus), and other animals using Cr-51. An alternative method for energy metabolism studies does not use an inert food market. A technique requiring determination of the weight of food eaten and the total weight of feces from that food can be employed. This is called the total collection method for determining a coef- ficient of metabolizability of a diet. This technique was used by Seibert (1949) to obtain metabolizability informa- tion for juncos, white-throated sparrows, English sparrows, blue jays, and field sparrows and by Kendeigh (1949) in studies with the English sparrow. Polyakov (1959) fed chick— ens at different times and then killed them simultaneously to determine how far food had progressed in the tract and to see how much digestion had occurred in the food. LeFebvre 18 (1964) used D20 to estimate CO2 and gaseous exchange in pigeons. output, water turnover, Although this review of previous investigations is by no means complete, it is indicative of the extent to which markers have been used in digestion and passage rate trials, and of the number of different species tested in bioenergetics studies. Why study bioenergetics? Certainly, for domestic stock the reason is obvious. It is highly desirable to know the energy requirements of the animals one is tending and to know the most economical feeds for satisfying these require— ments. The reasons may not be so clear with regard to wild— life. However, if one knows the energy requirements of a species and the usable energy supply available to that species in an area, then the carrying capacity of the area can be predicted or a population on the area can be esti- mated. Foods of greater energy value can be given more consideration in planting programs if the bioenergetics of the animal species present are known. The level of energy available may be a limiting factor to some species. Zimmer- man (1965) suggests that the northward distribution of the dickcissel may be limited by the "magnitude and duration of productive energy available for reproduction." The deter- mination of the nutritive efficiency of various animals with respect to different foods is, of course, important in appraising the usefulness of these species to man, in com- parative analysis with domestic stock, and in physiological, ecological, and evolutionary studies. Thus, studies of the energy metabolism of wild species are valuable. The objectives of this study were to learn whether chromium-51 labeled foods would enable the ready determina— tion of: 1. Patterns of food passage through the digestive tract. The quantities of crOp and/or gizzard contents which are digested and replaced per unit time. The dry weight of excreta derived from chromium—51 marked crop or stomach contents. The calorific values of certain foods and of their related excreta. The minimum and maximum durations of food transit in the digestive tract as affected by diet. The patterns and extent of cecal influence on a particular diet. The effects of age and sex on caloric requirements and on nutritional efficiency for a standard diet. An energy budget for the test species. It was also to be ascertained whether the Cr—51 method could be recommended as an improvement on other cur- rent methods of studying metabolizability and food passage rate. Initial research was directed towards development of techniques for accomplishing the objectives (developmental feeding trials) while subsequent efforts were aimed at applying the techniques using different individual pheasants and different diets (comparative trials). METHODS Materials and Equipment Browne (1922) showed that soluble dyes pass through the digestive tract of the fowl faster than hard food par- ticles, whereas insoluble markers pass at the same rate. He observed also that a successful marker must be physiologi- cally inert so as not to cross membranes. Certain chromium compounds, especially chromic oxide meet these two criteria. Cr51C13 also is nearly insoluble and inert in the GI tract. Cr-51 has a half-life of 27.8 days and emits gamma rays upon disintegration. The emissions of radioisotopes upon decay can be precisely measured to provide an estimate of the amount of isotope present. Comar (1955) describes the primary advantage of radioisotope use as "the great sen— sitivity of measurement usually available." An isotope offers advantages in quatitative measurement over the use of rubber pellets, beads, etc., and in simplicity of mea— surement over chromic oxide and other dyes which must be measured spectrophotometrically. Foster (1963) describes Cr—51 as "one of the least hazardous radionuclides." This is desirable for both the experimental animal and the eXperimenter. Chromium is toxic in high concentrations, but up to 100 parts per million (ppm) as the compound NaZCrO4 did not affect the performance of poultry chicks (Romoser gt_§1., 1961). Levels of Cr—Sl used in this study were less than this. Ionizing radiations sufficient to sterilize foods do not affect the gross energy, metabolizable energy, or macronutrient content of those foods (Levy g£_31,, 1959). In mammals, "orally administered Cr51C13 was almost totally excreted in the feces at the end of four days. Less than 0.5 percent of the dose was absorbed from the gastroin- testinal (GI) tract as indicated by tissue distribution studies. Although the urinary excretion indicated a higher level of absorption, the urine radioactivity was probably due to fecal contamination" (Visek §£_§1., 1953). Roche g£_31. (1957) demonstrated that "practically negligible" amounts of Cr-51 introduced into the human GI tract were absorbed. Hughes (1966) labeled proteins with Cr-51 in an effort to locate catabolic loci for protein breakdown. His reason for using chromium "lies in the extreme sluggishness of the exchange reactions of chromic complexes." Stacy and Thorburn (1966) stated that "after intraruminal administra- tion (to ewes) very little Cr51—EDTA (ethylene diamine tetra— acetic acid) is absorbed from the gut." Hogan (1964) made a 51 similar statement regarding the use of Cr —EDTA in sheep; however, Downes and McDonald (1964) found that some urine 51 contamination with Cr -EDTA always occurred after intraruminal administration "with the maximum amount being 4.7 percent of the dose." Mautz and Petrides (1967) found no detectable urine radioactivity in white-tailed deer (Odocoileus virginianus) which had ingested foods labeled with Cr51C1 . 3 In pheasants, too, it appears that Cr51C13 is inert. No tissue or blood radioactivity was detectable in pheasants used in the present study. Doses used were considerably smaller than those used in the above studies (0.05 to four microcuries (uc) as compared to 50 to 500 uc) however, mak- ing detection of a small tissue contaminant impossible or at least unlikely. Scintillation detection is the most satisfactory method of measuring the quantity of Cr-51 in a sample (Foster, 1963). This measurement is called "counting" and "counts" are detectable disintegrations registered by the counting equipment. A Nuclear Chicago Well Scintillation Detector System (BS—202V) with an 8725 analyzer scaler was used in this study. Caloric values of all feeds and the excreta from these feeds were determined with a Parr Oxygen Bomb calorimeter. During feeding trials, birds were held in test pens 14 x 14 x 14 inches in size. Each pen was raised to allow freezer paper 24 inches wide to pass under it (waxed surface upward) for collecting defecations. A freezer paper roll 10 was placed behind the pen and was unrolled and pulled under the pen constantly by being attached to a motor placed 12 to 14 feet in front of the pen. Since the paper moved at a rate of 14 inches per hour, it was possible to determine accurately when defecations occurred. A similar system was used by Petrides (1964) in his studies. Pheasants were maintained both in outdoor enclosures and in small indoor pens. They were put into one of the test pens at least seven days, and usually ten to fourteen days prior to their use in a feeding trial so as to accli— mate them to the test conditions. The laboratory used for developmental tests was not fitted for temperature or light control, thus both factors varied somewhat during eXperi- ments. The room used for final comparative tests (see beyond) was maintained at a constant temperature of 78°F. The relative humidity was kept at between 35 and 45 percent, and the lights were automatically turned on and off each day to provide an invariable 14 hour period of light. One bird never became accustomed to these conditions and was not used, but the other specimens adjusted remarkably rapidly. The test room normally was visited twice a day at regular times to collect excreta. Wild pheasants, captured by the Michigan Conserva— tion Department, were used in the development of techniques. Those birds employed in the final comparative trials (see beyond) were all from the same brood though obtained from a 11 pheasant breeder. Pheasant chicks were also purchased locally. The primary test ration was Turkey Breeder Pellets made by the King Milling Company of Lowell, Michigan. The guaranteed analysis of this ration was: Wheat middlings . . . . . . . . . 100 lbs Yellow corn meal . . . . . . . . 1,120 lbs Ground oats . . . . . . . . . . . 100 lbs 45% soybean oil meal . . . . . . 200 lbs l7/20% dehyalfalfa . . . . . . . 100 lbs 50% meat/bone scraps . . . . . . 100 lbs 60% fish meal Menhaden . . . . . 100 lbs Dried whey . . . . . . . . . . . 50 lbs Brewers dried yeast . . . . . . . 40 lbs Iodized salt . . . . . . . . . . 10 lbs Dicalcium phOSphate . . . . . . . 20 lbs Ground limestone, 38% calcium . . 50 lbs M—4 Vit. trace mineral premix . . 5 lbs Carbosep . . . . . . . . . . . . 2 lbs 1,997 lbs Whole corn and chokeberries (Pyrus melanocarpa) also served as experimental feeds in two trials. All food (Cr- 1abeled and unlabeled) and water was available ad libitum in all feeding trials. Suitable Techniques in Develgpmental Trials gingle-Dose Technique A single-dose was a single Cr-labeled piece of food (e.g., pellet) fed to a test animal. Initial trials indi- cated that the time required for complete passage of a sin— gle dose through the GI tract varied directly with the level of the Cr-51 dose. Ultimately, however, the minimum dose 12 level was found which was large enough to make passage rate independent of dose level. Doses were prepared from stock CrSlC13 solutions which had specific activities of 57.9 to 181 millicuries (mc) per milligram. Cr-51 levels of 304 counts per minute (cpm) (0.05uc) to 21,252 cpm (3.54uc) were applied to single pellets using Lambda (0.001 milliliter) pipettes in a pipette syringe. Although various levels of the radioisotOpe were used, approximately ten lambda of solution were used in all cases. All labeled foods in all tests were fed just after 8:00 a.m. on the first day of the test. Excreta collections were continued until after it was ascertained that all labeled materials had been defecated. After feeding labeled foods, the motor pulling the excreta collecting paper was started. This device was stopped at 8:00 p.m. when hourly excreta samples were placed in tubes. Fresh paper was then attached and the collecting device was restarted. This pro— cedure was repeated daily at 8:00 a.m. and 8:00 p.m. for the duration of the test. It was necessary to dry excreta samples in test tubes at llO-lZOOC for 24 hours to reach a constant dry weight. This temperature is higher than those used in most other studies. Manoukas gt_§l, (1964) has suggested that poultry excreta dried at 65°C or higher will suffer a signif— icant loss in gross energy but this situation could be over- come by using fresh excreta in a bomb calorimeter with 13 N,N-dimethylformamide as a combustion primer. The drying process thus would be eliminated. Since obtaining a constant dry weight for the excreta samples was desirable, a test was performed to deter- mine the energy 1035 of excreta dried at 110-1200C. Three fresh defecations were cut in half and one-half of each was put into a tube and dried for 24 hours at 120°C. The other three halves were immediately subjected to calorimetry usingi N,N-dimethylformamide. Caloric value of the three dried halves was determined after 24 hours of drying. The three dried samples had an average caloric value of 3,195 calories per gram, while the average was 1,012 calories per gram for the three fresh samples. The dry matter content of the moist excreta was 31.5 percent. Thus, the calories per gram of dry excreta converted to a fresh basis (3,195 x 0.315) was 1,006 calories per gram. No significant energy loss was found to have occurred due to the drying technique used. Possibly a different drying procedure (e.g., in a large flat container rather than in a tube) would result in an energy loss as described by Manoukas §£_§l. (1964). After samples were dried they were weighed. The weight of the dried excreta was measured to the nearest ten- thousandth gram on a Mettler balance (Model H). After weigh- ing, the radioactivity of each sample was counted and the count per minute (cpm) was converted to a per gram basis. All counts were corrected for decay and background error. 14 Only counts which were twice the background level (usually ten cpm) were used in computations. The weight of the food eaten was determined for each feeding trial. Samples of each ration were dried in tubes at 110-1200C for 24 hours to determine their dry weight and the weight of all fresh feed eaten by the birds was con- verted to dry weight. The weights of all materials dis- cussed in this report are on a dry basis unless otherwise specified. Knowing the total dry weight of food eaten over a several-day period and the total weight of the dried excreta from the food permits the computation of a metabolizability coefficient. Labeling foods with Cr-Sl enables determina— tion of the excreta which were derived from those foods. The formula used for this total collection method, as preé sented by Kleiber (1961, page 254) is: Metabolizability = 1-- total excreta wqt. coefficient total food Wgt. x 100 Continuous-Dose Technique A continuous-dose is a supply of uniformly-labeled food fed to the test animal over a somewhat prolonged period of time. Preparation of Cr-labeled food for a continuous- dose required dilution of an appropriate aliquot of the stock isotope solution and spraying the diluted preparation onto food with an atomizer. After spraying, samples of the 15 sprayed food were counted to determine the average cpm per gram of the food used for each trial. The doses used varied from 31 cpm (0.005uc) per gram of food to 184 cpm (0.04uc) per gram. Doses larger than 100 cpm (0.02uc) per gram of food were most satisfactory since detection of radioactivity in very small excreta samples was difficult with smaller sized doses. The sprayed food was presented to the bird or birds to be tested and the excreta collecting device was started. Subsequently, excreta were collected, dried, weighed, and counted as in the single—dose procedure. Feeding of a continuous-dose allowed determination of a metabolizability coefficient by the ratio method. The formula normally used (Sibbald et a1., 1960) is: amt . labe l/gm fee dJ metabolizability = x amt. label/gm excreta. coefficient 100 For Cr-Sl, the amount present per gram of both food and excreta was measured as cpm. Knowing the metabolizability coefficient for a diet, and the caloric values of both the diet and the excreta from it, one can determine the metabolizabile energy (M.E.) per gram of the diet. M.E. per ==gross energy __nonmetabolizabil-_ gross energy per gram food per gram food ity coefficient ‘ gram excreta 16 A common modification of the latter formula includes a factor to correct for the nitrogenous materials in a diet that are retained in the body without being metabolized. The M.E. of a diet is the energy available for metabolism (gross energy minus fecal and urine energy). Thus, the energy of the nitrogenous material in a diet which is retained by the body but does not undergo metabolism in the body should be subtracted from the M.E. of the diet (or added to the excreta energy). The nitrogen correction is made in order to convert all M.E. values of diets to a basis of nitrogen equilibrium for comparative purposes. The use of a nitrogen correction is not universal hence it was not used in this study. Baldini (1961) stated that in his study, the correction for nitrogen retention did not affect the M.E. values of the diets tested relative to each other. He stated further that "there is some question in the author's mind as to the practical value of such a correction." Swift and French (1954), in regard to the cor— rection, said that "it is difficult to justify the enactment of a penalty from a ration resulting in the storage of 25 calories as protein and 75 calories as fat in comparing it with one resulting in storage of 10 calories as protein and 90 calories as fat." According to Hill et a1. (1960), the correction is not uniformly used so it is apprOpriate to use the term "nitrogen-corrected metabolizable energy" to dis- tinguish values obtained in this way. 17 Previous investigators (Olsson and Kihlen, 1948; Dansky and Hill, 1952; and Mueller, 1956) have recommended that eXperiments employing the ratio technique run for several days because of variable indicator concentrations in individual excreta samples. The results of this study showed variation in Cr—51 concentration between hourly excreta sam- ples, between averaged hourly samples from day and night periods, and between daily averages of the hourly excreta samples (Table 1). However, there was also considerable variability in the Cpm per gram of the individual food sam- ples used in each trial. Thus, an F-test was used to deter— mine if the variance in the cpm per gram of excreta multi- plied by the nonmetabolizability coefficient of the diet, would be significantly different from the variance in the cpm per gram of foods. Only the cpm per gram of intestinal excreta samples occurring during the plateau period (see beyond) were used in the analysis. The cpm per gram of cecal excreta samples were not used because they represented food which was more thoroughly digested and thus had a coef- ficient of nonmetabolizability different from that of intes- tinal excreta samples. The analysis showed in all cases that the variance in the cpm per gram of excreta was not significantly differ— ent (P < 0.05) from the variance in the cpm per gram of the food from which it came. In other words, the observed vari- ability in Cr—51 concentration between excreta samples was 18 Table 1. Counts per gram of excreta from continuous-dose feeding trials with pheasants fed Turkey Breeder Pellets, Michigan State University, 1966 and 1967 Average Number of Daytime Nighttime of Hourly Expmt. Samples Average Average Samples For Number Per Day For Each Day For Each Day Each Day 8a 15 50.4 50.4 50.4 20 81.5 74.8 78.5 21 101.8 98.5 100.4 8b 13 74.7 55.6 64.3 19 74.0 64.9 70.1 8c 20 232.6 224.0 228.3 23 260.9 197.8 236.2 21 246.6 194.5 226.8 8d 22 275.3 266.9 271.5 22 294.4 318.2 304.1 22 350.1 355.3 351.9 10a 15 547.0 437.0 488.0 38 582.0 380.0 494.0 due to the variability of indicator concentration in the labeled foods. Some differential digestion apparently took place, however, since a consistent difference in the cpm per gram of excreta between day and night and between cecal and intestinal samples did occur. Based on these findings, one day trials using the ratio method were deemed justified, but no less than one full day because of differences in Cr-Sl concentration between day and night samples. Elam et a1. (1962) have 19 indicated that shorter feeding trials provide more accurate metabolizability results if, as in the present study, total collection of the excreta is accomplished. Perhaps food labeled in the customary manner (i.e., mixed with powdered chromic oxide) or sample collection by "grab samples" would result in higher variability in indicator concentration between excreta and food samples and thus require longer collection periods. The Ultimate Combination Technique in Comparative Trials Results of developmental feeding trials indicated that both the single-dose and continuous-dose methods should be used in a combination technique to best meet all objec- tives. Thus, a 24-hour continuous-dose feeding trial fol- lowed by a single-dose trial after sufficient time for foods from the first dose to pass completely through the tract (24 hours was always sufficient) were accomplished. The contin— uous-dose permitted the determination of metabolizability coefficients by the ratio method. The single-dose provided information on the passage rates of foods. Records of the total amounts eaten and defecated during both trials allowed determination of metabolizability by the total collection method. Approximately 96 hours was required for the perfor- mance of this combination technique with time allowed for complete passage of each type of dose. 20 The combination technique was used in a series of comparative trials to determine the amount of variability that could occur in the findings from trial-to—trial with the same male, with different males, with females or chicks, and with different diets. To determine the extent of vari- ability in passage rate, etc. between males, two birds were tested simultaneously in two separate tests. The dose levels used in these trials were at least 100 cpm (0.02uc) per gram of food for the continuous-dose and 10,000 Cpm (1.67uc) for the single-dose. RESULTS Results of Single-Dose Developmental Trials Collection, drying, weighing, and counting of radio- active waste material following the feeding of a single-dose yielded hourly information on the cpm per gram of excreta (Table 2). Graphs of these data showed the rate and pattern of isotOpe defecation. The pattern which was typical of all single—dose feeding trials (Figure 1), revealed that the Cpm per gram of the second radioactive excreta sample had the highest cpm per gram, with subsequent hourly samples display— ing regular decreases in isotOpe levels. A reasonable explanation of this defecation pattern seems to be that the first sample has a lower Cr-51 concen- tration apparently because it was passed along the intesti- nal tract before the label was mixed thoroughly with all materials present in the crop and/or stomach. Thus, this sample contained some unlabeled food materials. The second sample had the highest Cr—Sl concentration because the label had become thoroughly mixed with all the crop and/or stomach contents when this sample was passed. Subsequent defecation samples had proportionately lower Cr-Sl concentrations as they became mixed with more newly ingested unlabeled digesta. Eventually defecations with no detectable Cr-Sl occurred. 21 22 Table 2. Data of experiment 4b from which Figure l was derived, Michigan State University, 1966 and 1967 Time Elapsed Cpm Per Percent of From Ingestion Excreta Cpm of Gram of Total Cpm of Cr-51 (hr.) Wgt. (gm.) Excreta Excreta Per Gm. 1 0.0174 ... ... ... 2 0.2868 3,402 11,862 24.99 3 0.1866 4,127 22,117 46.60 4 0.4226 1,894 4,482 9.44 5 0.5335 291 545 1.15 6 0.3501 47 134 0.28 7 0.4463 42 94 0.20 8 0.6359 27 42 0.09 9 0.3753 13 35 0.07 11 0.3173 15 47 0.10 11* 0.1079 440 4,078 8.59 21* 0.2612 614 2,351 4.96 28* 0.0962 155 1,611 3.39 51* 0.5489 33 60 ._QL13 Total 47,458 99.99 *Cecal excreta. Figure 1. 23 Defecation rate and pattern for a ring-necked pheasant after ingestion of a single-dose of Cr-51 on a Turkey Breeder Pellet. Michigan State University. Experiment 4b, 1966 and 1967. excreta Cpm/gm 100,000? 24 0 it I0,000 1 (D o =intestinat defecation sample 0 =cecal defecation sample G) x = point determined by regres‘ sion formula t,000- G) I IOO - . G) i '0 1 L l l l I ll 2: 3| 4| 5| unnoc Ac'tcn IRICECTIAM n: I ADC! tn cnnn 25 For convenience, the defecation with the highest Cpm per gram is here called the peak defecation. The one or more defecations of the period prior to the peak represents a mixing phase, and the period following the peak is named the‘pqrqinquhase. A line was fitted statistically to the plotted data by means of a calculation using the least squares regression formula (Dixon and Massey, 1957; page 193). In the computa- tion of this line, the Cpm per gram of mixing phase and cecal defecations were not used. This calculation also indicated the proportion of the isotOpe defecated per hour from the total amount of isotOpe remaining in the bird after each defecation (i.e., the percentage rate of food passage per hour). The straight line character of the plotted data indicates that a constant proportion of the isotOpe remain- ing in the bird is defecated per unit of time. Although Cr-51 seems to be defecated from the ceca in the same pro— portional manner, the proportion of Cr-Sl defecated per hour obviously is much lower (thus the cecal passage rate is slower) than for intestinal defecations. Cecal excreta are readily distinguishable from intestinal excreta in gallina- ceous birds (Leopold, 1953). Perhaps the proportion of isotOpe passed per hour in the final intestinal defecations is slightly different than that of the initial defecations (Figure l). A second line could be constructed on the graph for these defecation 26 samples. However, these samples are of minor significance and of much lower magnitude compared to the initial points so no such calculation was made. Radioactive wastes also gave information on the rates of passage of foods through the GI tract. For the standard Turkey Breeder Pellet diet, the average minimum passage time was one to two hours, and the average maximum time for digesta not receiving cecal digestion was 8.5 hours. For those materials receiving cecal digestion the average passage time was 35 hours (Table 3). Metabolizability coefficients also were determined through these tests. By the total collection method the metabolizability of Turkey Breeder Pellets averaged 65.48 percent (Table 3). The extent of cecal digestion (discussed beyond) was also ascertained. A lower than normal rate of ingestion occurred in three of these developmental trials (experiment numbers 3b, 4a, and 4b; Table 3). This was probably due to the test bird undergoing a brief period of molting since a normal ingestion rate (experiment numbers 6a, 9a, and 9b; Table 3) followed this molting activity. Yet a higher rate of inges— tion was eXpected during molting. Marshall (1961, page 246) shows evidence that the metabolic rate of several species of birds increased during molting, but Davis (1955) concluded that "M.E. values of the English Sparrow (Passer domesticus) 27 .HQ Hmnfid: .mHmE uHsom u Hmlz .ouonEoocH mouooou u + .muoHHoQ Hooooun aoxusu n mme XNo.©m Rom.mo oo.mm eom o bIo h mIN NovN.N mIz no Rum.om xm¢.¢o hm.om mHm.m mN nlo m mIN omnN.N mIz mm RNm.n© XoN.mo mm.hm NmN.HN he th m NIH HmoH.N HHmIS mo $mn.¢m .XmN.mo wH.NOH mN¢.HH Hm HHIOH HH NIH mmoh.o HHmIS no XoN.mm Xmm.No «0.0m moo.mH we mIm 0H NIH moHn.o HHmIz we xm¢.Nn xmm.No Om.om hn®.m do oIm m HIo meh.o HHmIS Am :+ + + .+ mN elm OH HIo + Hmlz N :+ +, + .+ «m olm HH NIH +. Hmlz H usom\ommmmmm .mooo .>ooom Afimov .xmz .CHE .xmz .GHS coumm pHHm .oz ooom mo oumm .muoz .HHOO omon oNHm Hmoou HmcHumoucH HE\E® .umem amoucoouom Hmuoe unmouom omon Amunonv moumm owmmmmm homH cam momH .muHmHo>HcD oumum cmmH£UH2 .muoHHmm umoooum hexane pom mucmmmmnm :uH3 oSUchomu omooIonch any we quEQOHo>oc on» mcHusp poEHomnom mHMHHu maHoomm HmIHO Eoum omchm COHumEHomcH >UHHHQHummmHQ .m oHQMB 28 before and during molt were not significantly different at comparable temperatures." The developmental trials were not conducted in the controlled environment room, so metabolizability information might be eXpected to fluctuate with the variable environmen- tal conditions. Varying the Cr-51 dose level affected the measure- ment of the time of passage directly when the dose was smaller than 10,000 cpm (1.7uc) (Figure 2). If materials are removed from the GI tract in a regular proportional manner (see above), a smaller dose takes longer to be detect— able in the excreta and causes the minimum passage time to seem longer. Similarly, a detectable level disappears more quickly from the excreta and makes the maximum passage time appear to be shorter. Results of Continuous-Dose Developmental Trials The graphic representation (Figure 3) of the rate and pattern of defecation of the continuous-dose of Cr-51 shows mixing and purging phases, but the peak is replaced by a level plateau. This results from each defecation being thoroughly mixed with approximately the same amount of Cr-51 due the ingestion of a uniformly labeled diet. The plateau persists for a period corresponding to the time that the test bird is eating Cr-Sl labeled foods. The average of the cpm per gram of excreta (including cecal defecations) during Figure 2. 29 Relationship of minimum and maximum passage time to the size of the Cr-Sl dose in— gested by a pheasant. Michigan State University. 1966 and 1967. 3O DOSE LEVEL (Cpm) 2I’252 Innoooooo _______________________________________ l5,009 Xllooeoooo o o ________________________________________ H.425’u1000ooeeoe ........................................ 398 I 9 X1“... _________________ 3,677 XlO. 0'00 ___________________________________ amp"... I —I I i I r 0 IO 20 3O 4O 50 MAXIMUM PASSAGE TIME (hours) minimum intestinal passage time maximum intestinal passage time maximum cecal passage time 51 Figure 3. Defecation rate and pattern for a ring-necked pheasant after ingestion of a continuous-dose of Cr-Sl on Turkey Breeder Pellets. Michigan State University. Experiment 8d, 1966 and 1967. DOOM. owqwm<4 no Zoimwoz. 20mm Ommddow mmDOI 639:8 omov vmncommta omou o. m a 52 om om . on om on ow om Hi 1 4 1 q 1 Ease..." c0233: .33 "6 29:3 8:333 3552:. .... .6363 iii. A H _ i111- IIIIIIII I on I 00. o J 00m 100m III“ III! A A 33 the plateau period is compared to the average cpm per gram of food to determine metabolizability coefficients by the ratio method (Table 4). The Cr-Sl label allows identification of the excreta that are derived from labeled foods. Hence the total weight of ingested materials and their related excreta for the period of a continuous-dose test are known, and a metaboliza- bility coefficient also may be computed by the toal collec- tion method. Table 4. Digestibility information gained from Cr-51 feed- ing trials performed during the development of the continuous-dose technique with pheasants fed increasing doses of Cr-Sl with Turkey Breeder Pellets, Michigan State University, 1966 and 1967 Metabolizability Dose Coefficients Expmt. Grams Size No. Bird Eaten (Cpm/gm) Total Collection Ratio (%) (%) 8a M-RI 1 .8280 ' 31 59.62 58 . 96 8b M-RI 1.3032 33 62.97 48.97 8c M-RI 1.8784 118 64.47 51.24 8d M-RI 2.5927 142 63.21 54.05 10a M-RI 1.9931 197 58.35 59.96 ._.fi M-RI = adult male, number RI. 34 Results of Comparative Trials Using the Combination Technique Comparative feeding trials were performed in the controlled environment room using pheasants of the same age and lineage. Thus, there should have been only individual and sexual variability between birds. The combination tech— nique permits determination of both passage rates and metab— olizability of foods as well as other information such as the amount ingested per hour. Under controlled conditions these factors may be compared between birds, or, since there is no retention of Cr-51 (see above), within the same bird. A graph of hourly isotOpe defecation was constructed for each tiral by collecting, drying, weighing, and counting radioactive excreta (Figure 4). The continuous-dose portion of the combination tech— nique permitted the computation of a metabolizability coef- ficient by the ratio method. For comparisons, this coeffi- cient was also determined simultaneously by the total col- lection method. Since both methods were measuring the same factor, the coefficients determined by the two methods should have been approximately equal to each other in each test. They were different however, in almost every feeding trial (Table 5) and this situation has no obvious explana- tion. For cocks on the standard diet, the average total collection metabolizability coefficient was 63.49 percent while this average by the ratio method was 53.68 percent. Figure 4. 35 Defecation rate and pattern for a ring-necked pheasant during a com- bination technique feeding trial in which both single and continuous- doses of Cr-Sl were fed on Turkey Breeder Pellets. Michigan State University. Experiment 11a, 1966 and 1967. 36 noon. ammoo ...o 20:.mw02_ 20mm owma<4m manor 92:32.. oIeone uIb/uIda 03:32.. 88 0.9.? 92662 38 once negates 8 2. on on... 9. on soaswso 8 o. L o. d u d 1‘ 1 1 4 d 1 0 0 O . Ian I. O O I oo. . ills—.203 Illa . I. . e . . .e O . 0 O . . . . G 0 v o o o o . o . I can IooQ. O O 2252 .32 . -352 an 35.523 .52. a x . . 22:: 5:383 .33 u G I 000» 0153 5:333 .0522... u o . IR 0006. 37 Table 5. Digestibility information gained from’Cr51 feeding trials using the combination technique, three separate diets, and male and female pheasants, Michigan State University, 1966 and 1967 Size of %.of Size of Continuous- Single— Expmt. Single- Dose Dose Gm/Hr No. Bird Diet Dose (cpm) (cpm/gm) Recovered Eaten lla M-FI TBP 11,805 148 89.63 2.0062 11b M-FI TBP 13,129 163 86.18 1.8755 11c M-FI TBP 13,825 203 100.21 2.0192 11d F—HI TBP 22,615 178 98.09 1.8441 lle F-HII TBP 14,544 141 90.26 2.4743 11f M-FI Choke— berry 12,757 134 95.63 1.0490 11g M-FI Whole corn 11,113 82 103.69 1.8795 $12a M-FI TBP 18,378 142 103.53 2.0690 M-FII TBP 12,400 142 98.08 2.0127 012b M-FI TBP 10,170 163 98.51 2.2996 M-SI TBP 10,270 163 99.80 0.6624 *13a M-FI TBP 17,501 ... 99.81 2.2133 (*)13b M-FI TBP ... 136 ... 1.7744 TBP = turkey breeder pellets. M-FI = adult male, number FI. F-HI adult female, number HI. \ 38 Total Collect Ratio Passage Rates (hours) Meta. Meta. Calories/Gm Intestinal Cecal Coef. Coef. Metabolized Min. Max. Min. Max. 63.83 55.15 3,083 1-2 8 9-10 36 61.95 51.34 3,023 1—2 9 9—10 23 ‘61.79 53.87 3,018 1-2 7 9—10 34 65.24 56.16 3,131 1-2 28 7-8 69 67.02 58.65 3,188 1—2 10 8-9 46 48.54 35.89 2,114 0—1 30‘ 10-11 32 80.44 83.06 3,658 1-2 19 10-11 71 62.47 49.28 3,040 0-1 8 11-12 37 63.22 55.49 3,064 0—1 12 12-13 32 65.66 62.61 3,142 1-2 7 11-12 47 65.84 49.38 3,148 1-2 10 10-11 47 64.63 ... 3,109 0-1 11 8-9 48 62.02 52.28 3,026 ... .. .. .. 6 Trials in which 2 birds were tested simultaneously. * Single-dose test rather than a combination test. (*) Continuous-dose test rather than a combination test. 39 The single dose portion of the combination technique allowed determination of minimum and maximum passage rates of foods. For cocks on the standard diet, the average min- imum passage rate was 0.6 to 1.6 hours. The average maximum rates were nine hours for materials not receiving cecal digestion and 38 hours for materials which were partially digested in the ceca. Recovery of the Cr-Sl label from single-dose tests ranged from 86.18 to 103.69 percent. Recoveries greater than 100 percent are probably due to normal equipment error occurring both as the prepared dose is counted (before inges- tion) and when counting the collected excreta. Using the caloric values of the standard diet and of the excreta from that diet, the average metabolizable energy (M.E.) per gram of food was 3,073 calories for cocks. The average amount of the standard diet eaten by cocks was 1.8813 grams per hour. It is possible to obtain valid average results for passage rates, metabolizability, etc. in the comparative trials. However, to learn the differences in results using different diets, it is also desirable to compare the vari- ation in these results within and between cocks and hens in trials using the standard diet. Cock F-I was used in many of the comparative tests. The total collection metabolizability coefficients for the standard diet for this bird were constant within the rather 4O narrow limits of 61.79 to 65.66 percent. However, minimum and maximum passage rates and the amount ingested per hour were more variable. Labeled excreta first appeared within the first or second hours after ingestion of the Cr-51 dose. The maximum rate for intestinal excretion ranged from 7 to 11 hours and for cecal excreta from 23 to 48 hours (Table 5). The amount eaten by this bird varied between 1.7744 to 2.2996 grams per hour. In each of two feeding trials, two birds were tested simultaneously using the standard diet. Total collection metabolizability coefficients, calories of energy obtained per gram of food, and passage rates were all very similar for the two birds in each trial. But all of these measure- ments differed betweeen the two trials (Table 5). The amount ingested by the two birds was almost equal in the first trial and extremely unequal in the second. Although one bird ate in excess of three times as much as the other in the second trial, their metabolizability of food and passage rates were almost identical. The bird eat- ing less showed no significant weight change during testing and a normal amount of visceral fat was noted when it was sacrificed at the conclusion of the feeding trial. The results obtained from trials with hens as com- pared to those with cock F-I (on the standard diet) showed ‘a small difference in average total collection metabolizabil- ity coefficients, viz., 66.13 percent with hens and 63.49 41 percent with the cock. This is a small difference as is the difference in their ingestion rates; the cock ate an average of 2.0367 grams per hour throughout all feeding trials and the average for the hens was 2.1592 grams per hour during their feeding trials. The minimum passage rates were about equal for the two sexes, but the maximum passage time of the standard diet was considerably longer in hens (Table 5). With a longer passage rate, one would eXpect to find the higher digestibility which was observed for the hens. The longer passage rate may be in part due to less activity at night by the hens, as shown by fewer defecations. Thus, there was not a great deal of variability between birds tested simultaneously in feeding trials, but there was vari- ability between different birds in different trials and even in trials with the same bird to some degree. There was also some difference between cocks and hens. A controlled environment was not employed in the developmental trials and test pheasants were from wild stock. Thus, a comparison of the results from those trials with results from the comparative trials can help to determine the effects of the controlled environment. Average values for all cocks undergoing testing on the standard diet in the two types of trials were: 42 Food Passage Rates Total Grams (hours) Collection of Food Intestinal Cecal Meta. Coef. EatengHr. Min. Max. Min. Max. Develop- mental trials 63.54% 1.7768 0.9-1.9 8.5 9.5-10.5 39.4 Compara- tive trials 63.49% 1.8813 0.6-1.6 9.0 6.1-7.1 38.0 The comparison indicates remarkably little dissimi— larity considering the different conditions and pheasant stock used. One developmental test shown in Table 3 was excluded from the average since the dose level used was far below the minimum level found to yield reliable results. Evaluation of the results of trials in which either chokeberries or whole corn were fed allows some interesting comparisons. Corn had the highest metabolizability of the three diets used, while chokeberries had the lowest (Table 5). Similarly the M.E. per gram of corn was considerably higher than that of the standard diet and almost twice as much as that of chokeberries. The maximum passage rate of corn was much longer than that of Turkey Breeder Pellets or choke- berries. However, chokeberry materials which did not receive cecal digestion took much longer to pass than did such mate- rials in the other two diets. What are the relationships of metabolizability coefficients and the passage rates of food 43 and how would the relative value of a diet be accessed from these factors? Of course the standard commercial diet would be rated first among these three diets on the basis of the essential nutrients and vitamins it contained, but on the basis of the M.E., corn is highest. In terms of passage rate, corn would be rated third and chokeberries would be first. The following equation was used to provide an index to these relationships in this study: Av.M.D. per day = (M.E./gm X gm/hr eaten X 24 hrs) mi: hgzsg rate The product obtained within the first parenthesis tells the M.E. per day if the maximum passage rate of the diet being fed is one day. The term in the second parenthesis changes the M.E. per day to correspond to the actual passage rate of the diet. This computation incorrectly assumes that an equal amount of any unit of food is digested every hour dur— ing the passage of that food. Most food is digested very soon after ingestion and only a small proportion requires the full maximum passage time. However, the last 5 percent of a diet to be absorbed may very well be the most bene- ficial part so should not be ignored. And, the formula yields the average energy available from the food eaten per unit of time. 44 As an example, the average M.E. provided per day to bird F-I on the three diets tested was: Diet Averagp_M.E. Per Dpy, Turkey Breeder Pellets 87,334.9 cal. (87.3 kilocal.) Whole corn 55,771.6 cal. Chokeberries 39,916.5 cal. These results show the relative value of the diets when pas- sage rate is considered as well as the M.E. of a diet; they show that the standard diet provides more energy per unit of pimp. Thus, M.E. and passage rates considered together may be more important than either value considered alone. One of the earliest passage rate studies was accom- plished by Ewing and Smith (1917) with the steer. Hillerman g£_§1. (1953) found that marked food materials first appeared in the excreta of chickens and turkeys in less than five hours after feeding. Browne (1922) showed that oats first appeared in the excreta of fasted chicken hens in five to six hours after feeding. Radioactive barium has been used (Imabayashi §£_§1., 1956) to show that approximately one- half of the marked food ingested by poultry was excreted within four to five hours. The first appearance of excreta from food marked with chromic oxide in 21 coturnix quail was from one to two hours after feeding (McFarland and Freedland, 1965). The results of the latter two investigations are most in agreement with the findings of this study with regard to minimum rate of passage. 45 Study of food passage by means of X-ray shadows of BaSO4—marked food have shown that two ounces of oats were completely removed from the tract of chickens in 16 to 25 hours (Henry §£_§1,, 1933). And in the quail study men- tioned above, excreta defecated four hours after feeding showed no Cr203 but it again appeared after five to eight hours indicating the occurrence of cecal evacuation. Thus, the maximum passage rate for chickens appears to be longer than that of pheasants (if cecal influence is omitted), but that of coturnix quail appears to be shorter. With poultry, the passage rates of pullets and cooks may be slightly faster than for mature hens (Hillerman gg_gl., 1953). In this study, pheasant cocks exhibited somewhat faster maximum passage rates than hens. In previous studies, values other than M.E., espe- cially productive energy, have been given much attention. Now however, "there is general agreement that the energy value of the diet is best expressed in terms of the metab- olizable energy to which it gives rise" (Sturkie, 1965; p. 260). Hill (1964) states that "it has been found that M.E. values determined with chickens are essentially unaffected by the level of food intake, rate of growth or egg produc- tion, breed, sex, and wide differences in the nutrient balance of the diet." It has also been shown that there is no significant difference in the M.E. values between the sexes in the English sparrow (Davis, 1955). 46 In general, the present study is in agreement. M.E. values varied as much in separate trials on the same bird as between wild and game farm birds or between males and females (Table 5). Also, the level of food intake did not appear to affect the metabolizability of the diet (Table 5). The level of metabolizability of the standard diet, however, was about 5 percent higher for chicks than adults. Metabolizability coefficients averaged 68.68 percent for chicks and 63.49 percent for cocks in comparative runs. Additional Results Feedipqurials with Chicks The single—dose technique was used for all experi- ments with pheasant chicks. Because trials with adults were made concurrently, the excreta collecting device was not available for use in the chick tests. Based on results from feeding trials with adults, however, 24 hours was deemed sufficient to determine minimum and maximum passage rates for materials not receiving cecal digestion. In day-long tests, excreta were collected hourly for at least the first 16 hours. As in adult feeding trials, tests were started at about 8:00 a.m. The diet for the first five chick trials was Quail Breeder Mash commercially prepared by the King Milling Com- pany of Lowell, Michigan. Chicks were force-fed Cr-labeled mash since 3g libitum feeding might have resulted in spillage. 47 The chicks were accustomed to being handled and the proce- dure appeared to cause little stress. The guaranteed analysis for Quail Breeder Mash is as follows: Ground corn . . . . . . . . . . . 412.5 Soymeal dehulled 50% . . . . . . . 370.0 17%.A1fa1fa meal . . . . . . . . . 50.0 Dried whey . . . . . . . . . . 25.0 Meat/bone meal 50% . . . . . . . . 25.0 Fish meal Menhaden 60% . . . . . . 25.0 Ground limestone (CaCO3) . . . . . 50.0 Dicalcium phosphate . . . . . . . . 15.0 Iodized salt . . . . . . . . . . . 5.0 Vitamin premix l NOpCO M—4 . . . . 2.5 Fat . . . . . . . . . . . . . . . . 20.0 1,000.0 lbs. Turkey Breeder Pellets, the standard ration for adult trials, were used for the final three chick trials. The amount eaten per hour by the chicks increased fairly regularly until at the age of 78 days their ingestion rate was similar to that of adult birds (Tables 5 and 6). There did not appear to be a correlation between age and the metabolizability of feeds in this study, although Mueller §£_31. (1956) showed that the metabolizability of all nutri- ents in the diet of chickens increased slightly from two to four weeks of age and then declined steadily. In this study, the average metabolizability coefficient, 67.53 percent, was slightly higher than that of adult birds. The minimum passage rate (Table 6) did not appear to change with age during the first 11 weeks, but it was longer for chicks than for adults (Table 5). The maximum passage rate for materials not receiving cecal digestion increased 48 .UoGHEHouoO uoc mm3 muouoxo mo 05Hm> UHHOHMO n + .muoHHom upcomum hexane n mme .nmmz Hooooum HHmso u Ema .mudon ¢N How “umou no one um .uB mvom\umou mo uHmum um .uB moom u ©N\¢Ne Hmem.o NOH.m oe.oo «NA ho 0.0 NIH mmem.m new- omm\mmm HHIo on ones Uqfloum mmHm.o He~.m NH.Nk amA OHIm o.em mIN mHom.H ems mem\mmm HHIo ms nIms Hehv.o NON.m me.h© eNA nlo o.¢N NIH MHmm.H mmB mm¢\om¢ HHIU hm mlmh mHoh.o NN>.N om.oo OH olm 0.0 mIN mHhm.o Ema va\mmN HHIO Ne mm Hmoe.o mmH.m e~.ms ... ... m.OH m.~Im.H mmHo.H 2mg meH\NeH HHIo .om as momm.o eem.N Hh.m¢ ... ... m.h m.mIm.N onv®.o Ema mOH\mm HHIO HN on enmm.o + om.no ... ... o.m NIH mOHe.o Ema m¢\H¢ HIO mH on Nom¢.o + mN.Nm ... ... oqm mIN mmmN.o Ema «oN\¢N HIO h on ARV “now new ooom EU .mooo .xmz .GHS .xmz .CHS Amy: wNv uoHQ Hfimv US .02 Anamov .oz ommmmmm Hom.m.z .muoz Hmooo HmoHumoucH coumm zoom UHHm omm umoa poom mo oumm mo .Hmo .HHoo Hm\EU GHHm ommucooumm Hmuoa Amudonv moumm mmommmm homH com oomH .MDHmHo>H:D oumum :mmHnoHE .muoHo o3u cow monno ucmmmonm nuHB mHmHHu mchmom omooImHmch HmIHO Eoum COHumEHomcH usmHm3 Moon can huHHHQHumomHQ .o oHQMB 49 slightly up to approximately four weeks of age, but by 57 days the chicks passed these materials at the adult rate. Cecal excreta were not distinguishable as such, either by their appearance or by the delayed appearance of Cr—51, until the birds were 27 days old. Possibly the devel— opment of the ceca or of the cecal flora is inadequate for detectable cecal digestion until after 27 days of age. No previous investigations into this matter were discovered. In previous studies of passage rates in young and old birds, it was found that the passage of foods through young turkey hens was significantly more rapid than through old turkey hens (Hillerman g£_§1,, 1953) and the passage of feed through juvenile chickens was faster than through adults (Thornton gp_§1., 1956). However, Dorozynska (1962) found that "the Speed of passage of food down the alimentary canal increases as geese grow." At the age of 57 days, the chicks were switched from Quail Breeder Mash to Turkey Breeder Pellets and an immedi- ate increase in the maximum length of intestinal passage was noted. Neither the minimum passage rate nor the metaboliz- ability coefficient appeared to be affected however, by the pelleted diet (Table 6). When ground Turkey Breeder Pellets were fed, the metabolizability remained about the same as with whole pellets but the length of the maximum intestinal passage decreased to the level observed with a mash diet. 50 Possibly the gizzards of the chicks were not sufficiently developed to grind the pellets quickly. Four weeks is the recommended age at which to start feeding pellets (Warden, 1962), but this may be too early. The metabolizability of pellets evidently is as high as for ground pellets, so a chick receives the same amount of energy per gram from either form of the diet. But a chick gets less energy per hour with pellets, since they are passed more slowly. McIntosh §£_31. (1962) and Reddy §£_§1. (1962) have previously shown that the M.E. content of a diet is not changed by being fed as pellets or mash. And, it should be noted that slower passage did not result in a more complete digestion of food as might be expected (Table 6). A difference in passage rates was not observed when fasted young chickens were fed pellets or ground pellets marked with chromic oxide (Jensen gp_a1., 1962). The ini— tial appearance of marked excreta was two hours after feed- ing either mash, pellets, or ground pellets, and the last appearance of marked excreta was at approximately ten hours for all three diets. These passage rates agree well with those of pheasant chicks in the present study except for the pelleted diets which had longer rates in pheasant chicks. Other passage rate determinations for young chickens showed minimum passage times to be approximately 1.5 to 2.5 hours depending upon the test conditions employed (Tuckey §£_§1,, 1958). 51 Chickens have a metabolic rate which is low at hatch- ing but which increases until about 30 days of age. It then decreases to the adult level by 70 to 80 days of age (Kibler and Brody, 1944; Crandall and Smith, 1952). Apparently none of the data of this study can be adapted to indicate the metabolic rate of pheasant chicks at various ages. Both body weight and ingestion rate approximately doubled each week for the first four weeks, however, and then continued to increase but at a lower rate. Cecal Influence on a Diet The ceca harbor bacteria and function primarily in the microbial decomposition of crude fiber (Suomalainen g£_§1., 1945). The length of the ceca is related to the diet and they are longer in bud-eating birds like grouse than in seed-eaters such as quail and pheasants (LeOpold, 1953). Cr-51 is very useful in the study of cecal digestion. The percent of cecal influence can be determined from the data of a single-dose feeding trial by dividing the total cpm recovered in cecal defecations by the total cpm recov- ered from all excreta (including cecal). A cecal metaboliz- ability coefficient can be determined from the data of the continuous-dose feeding trial by using the average cpm per gram of cecal excreta for the plateau period only in the formula for determining metabolizability by the ratio tech- nique (shown above). The maximum passage rate for materials 52 requiring cecal digestion is a measure of the length of cecal influence on a meal. The rate of cecal defecations as compared to intestinal (rectal) defecations per day is aifurther measure of cecal activity. The percentage of cecal influence on a meal was highest with the whole corn diet. This was expected since corn has a higher concentration of crude fiber than the other diets tested. The average percentage of cecal Cr-51 which was recovered from birds on the standard diet was 10.49 for males and 13.59 for females (Table 7). Accord- ingly, it is possible that females may depend more on cecal digestion than males and this may explain why total collec- tion metabolizability coefficients were higher for females than for males. The slower passage rate in females, however, also may help to explain their higher metabolizability coef- ficients on the standard diet. A portion of a diet which received both cecal and intestinal digestion had a higher metabolizability coeffi— cient than one receiving only intestinal digestion (Table 7). Metabolizability of the standard diet showed an average increase of 11.32 percent for pheasant F—I due to cecal digestion. With the chokeberry diet, the metabolizability coefficient for materials which received both cecal and intestinal digestion was lower than that for materials which received no cecal digestion (Table 7). The only apparent explanation for this last case is that the relatively 53 .muouoxo HmcHumoucH H “Hm HoQEDG .onEow DHSUM Hmlm “mumuoxo Hmooo “Hm HoQEsc .onE uHspm Hmlz “muoHHom Hopooum moxHSE I mme .coHumomHU Hmooo po>HmooH uH NH poom.mo wuHHHQmNHHOQmuoE any CH ommouooH unwouome mm.o mN.Nm oH.mm ... ... oo.N mme HMIS QMH HIM: HH ... ... ... vim: we Hh.0H oo.N mme thz omH HIHS OH om.hH mm.mv em.©© Ola: he mo.mH oo.N mme Hmlz HIM: h wo.@H Ho.No mo.mn Ola: he mm.0H oo.N mme HMIS QNH HIM: NH mh.m m¢.mm mN.mo DIM: Nm mm.m oo.N mme HHmIS HIM: m mm.ON mN.m¢ SH.0h OIH: hm Hm.m oo.N mma HMIE mNH HIM: mH cuoo no.0H oo.mm mH.mm Ola: Hm mo.om oo.N .oHon3 Hmlz mHH Hlun om muuon ... mm.mm HN.om Ola: Nm mm.bH oo.m onoco Hmlz MHH HIM: 0H NN.NH mo.mm hm.on DIM: we mm.mH oo.N mmB HHmIm oHH HIM: mN . OH.m oH.om 0N.¢m Uluz mo mN.HH mh.N mmB Hmlm UHH HIM: h . om.wH hm.mm MN.on OIHc em mo.m oo.N mme HmIS oHH HIM: m m©.m em.Hm mm.®m Olun MN om.¢ om.N mme Hmlz QHH HIM: m mo.N mH.mm mN.hm DIM: om Hh.m mN.m mmB thz mHH Re any ARV esoHumomHQ HmoHumoucH HmooO mucosHmcH umHQ m. mmm\oomon uoHn oHHm .02 CH ommmnocH muaoHonmooo HmooO mo moroccosHm, Hmomo umoe udouuom muHHHQMNHHOQmumz COHumuda IcH HmooO. No.02 .>¢ , oosumz 0Humm mmoufioouom homH pom momH .muHmHo>HcD oumum cmmHsoHE .muoHp msoHum> co mucmmmocm poxooCImcHu uHsom mom mocosHmcH Hmooo no common .n oHQme 54 undigestible fibrous portion of the diet was diverted to the ceca. This caused the cecal excreta to have a higher propor- tion of undigestible material than intestinal excreta in relation to the amount of Cr-51 present. The lower cpm per gram of cecal excreta apparently lowered the cecal metaboliz- ability coefficient. Materials receiving cecal digestion had a longer maximum passage rate than materials not receiving cecal digestion. For all tests with the standard diet, the pas- sage rate averaged 30.00 hours longer for materials receiv— ing cecal influence (Table 7). The average minimum cecal passage rate for the standard diet was 7.9 to 8.9 hours. The average number of cecal defecations per day was slightly over two for all feeding trials. For specimen F-I for which data were most complete, the ratio of cecal to intestinal defecations on the standard diet was 1 to 24.04, and for this bird on a corn diet the ratio was 1 to 29.4. The ratio of cecal to intestinal evacuations for chicken hens is 1 to 11.5 after ingestion of corn and 1 to 7.3 after feeding barley (Rosseler, 1929). Apparently cecal digestion is less important to pheasants than to chickens. Cecal defecations of pheasants occurred most frequently near 7:00 a.m. and 7:00 p.m. (Table 9). 55 Caloric and Moisture Content of Feeds and Excreta Caloric values of the three adult diets used were somewhat similar (Table 8), ranging from 4,239 to 4,485 calories. The amount of moisture in all excreta was approx— imately 70 percent (Table 8). Fresh excreta were used in determination of this percentage. Passage Rate of the Cr-51 The question of whether the Cr-51 label passes through the tract at the same rate as the food on which it is applied was studied briefly. Excreta from chokeberries are characteristically colored dark blue. A Cr-51 labeled chokeberry was fed to a bird whose previous diet was Turkey Breeder Pellets. A pure diet of chokeberries was presented to the bird with the labeled berry. Defecations subsequent to ingestion of this label were monitored and a qualitative estimate of the "blueness" of each defecation was made. Each defecation was also checked for the presence of radio- activity. The first appearance of blue color in a defeca- tion coincided precisely with the first detection of radio- acitivity. Blueness increased in the next defecation as did the amount of radioactivity, providing a mixing phase and peak when graphed. Subsequent defecations maintained a con- stant level of blue color as eXpected on a continuing berry diet, while the purging phase of radioactivity was observed. 56 Table 8. Calories per gram and percentage moisture of feeds and excreta from both juvenile and adult pheasants, Michigan State University, 1966 and 1967 Bird Excreta on a Diet of Age QBM TBP Chokeberry Corn 22 days 3,057 cal 70 % 42 days 3,026 cal 72 % 57 days 3,187 cal 70 % 69 days 3,578 cal 67 % 76 days 3,391 cal 70 % Adult male 3,195 cal 4,608 cal 4,079 cal 68.5 % 71 % 77.5 % Adult female 3,187 cal 69 % Diets QBM TBP Chokeberry Corn 3,912 cal 4,239 cal 4,485 cal 4,456 cal 10.4 % 9.2 % 68.7 % 9.1 % QBM = Quail Breeder Mash TBP = Turkey Breeder Pellets 57 It appeared that the label does indeed pass at the same rate as the food on which it is applied. There were other evidences, too, contributing to this conclusion. There was, for example, a consistent occurrence of a regular percentage removal of the isotope from the digestive tract. If the isotope was not associated with the food in the tract, it could pass in a single defecation rather than in propor- tional amounts in successive defecations. There were also close associations of the isot0pe with cecal defecations which, if the isotope had passed independently of the food, would not have occurred since the label would not be ex- pected to be divided between the intestine and ceca in any particular pattern. Daily Cycles of Ingestion, Digestion, and Excretion The average amount of food eaten by a pheasant dur- ing daylight hours in the controlled environment room was 46.51 grams per hour, while only 2.47 grams per hour was eaten at night on the average. The variation in the digestibility of foods between day— and nighttime was discussed earlier. One would eXpect nighttime digestibility to be higher than daytime in the diurnal pheasant since less is eaten at night and less is defecated. Therefore passage rate should be slower and digestibility should be greater. Pheasants, however, show a higher digestibility during daylight hours. The reasons for 58 this could be that because less food is eaten at night, less Cr-Sl label is consumed. Thus, each defecation at night has a lower proportion of food material, less Cr—51, and more wastes such as sloughed cells and nitrogeneous kidney wastes. This would give a lower Cpm per gram excreta for nighttime defecations and cause nighttime digestibility to appear to be lower than in daytime. The average number of defecations per hour for pheas- ant F-I in the controlled environment room on the standard diet was considerably less during darkness than when the lights were on (Table 9). The most active excretory times were just after the automatic lights were turned on and just before they were turned off. Since the peak appearance of Cr—Sl occurs one to two hours after ingestion of a single-dose, the major proportion of the excreta associated with the food that it marks must also appear at this time. When the amount of Cr-Sl found in each defecation is expressed as a percentage of the original dose and this percentage is multiplied by the weight of its respective defecation, the sum of the products was found to vary from 0.3 to 3.4 grams. If these sums are assumed to be the total weights of the excreta from the food associated with the Cr-Sl label during the mixing phase, then these weights divided by the nonmetabolizability coefficient would indicate the original dry weight of the food with which the label was mixed. The broad range of weights (0.3 to 3.4 59 Table 9. Defecation rates for pheasant F-I during seven feeding trials in the controlled environment room on the standard diet, Michigan State University, 1966 and 1967 Average Average Intestinal Cecal Hour Defecations/Hour Defecations/Hour 0830-0930 3.3 0.0435 0930-1030 1.9 0.0 1030—1130 2.5 0.0 1130-1230 2.6 0.0 1230—1330 2.0 0.0435 1330-1430 2.3 0.0 1430-1530 3.0 0.0870 1530-1630 2.9 0.1304 1630-1730 3.4 0.2174 1730-1830 3.0 0.1304 1830—1930 4.2 0.3043 1930—2030 2.6 0.1304 2030-2130* 3.9 0.2174 2130-2230 0.5 0.0 2230-2330 0.7 0.0 2330—2430 0.9 0.0 2430-0130 1.3 0.0 0130-0230 1.6 0.0 0230-0330 1.4 0.0 0330-0430 2.3 0.0 0430-0530 0.8 0.0 0530-0630 1.6 0.0435 0630—0730** 3.2 0.6087 0730-0830 2.2 0.3478 54.1 2.3043 = average defecations/ day *Lights turned on daily. **Lights turned off daily. 60 grams), however, makes it difficult to determine in which organ mixing actually occurs. This makes the determination of the dry weight of excreta associated with the Cr-Sl marked crop or stomach contents (objective three above) of uncertain value. Autppsy Findings As each feeding trial was concluded, the bird was usually sacrificed to determine whether remnant Cr-51 could be detected in its body. Although twelve separate tissues and blood were checked in each of four birds, no significant traces of radioactivity were found. Further evidence that Cr-51 is essentially inert physiologically is the high rate of its recovery. An average of 95.96 percent was recovered in 16 single-dose trials in which the standard diet was fed (Tables 3 and 5). Other birds were sacrificed to determine the distri- bution of Cr—51 in the alimentary tract after feeding either a continuous- or a single—dose. By examining digesta sam— ples from sacrificed birds which had been fed a continuous— dose, information was sought concerning the region of the tract in which most absorption of nutrients occurs. It was reasoned that the higher the cpm per gram of digesta the greater the removal of nutrients through absorption. Only two pheasants were subjected to this type of test and the results were not conclusive since radioactivity 61 could not be detected in some digesta samples (Table 10). If larger doses were used, however, and larger samples were taken from each segment of the tract, this difficulty pos- sibly could be overcome. In the present tests, the cpm per gram of digesta increased at about the middle of the small intestine (Table 10), and much absorption may have occurred in the anterior small intestine. Six chicken hens were fed single—doses and then killed individually 17, 31, 60, 91, 121, and 148 minutes afterwards, respectively. Their alimentary tracts were removed, opened, and digesta samples were taken. When dried and weighed, the samples were counted to determine the dispo- sition and concentration of Cr—Sl in each segment of the tract. (An alternative method would be to arrange the entire tracts on X-ray plates for eXposure, so that a photo- graphic indication of the location and amounts of radioiso- tope in the tract could be gained.) In the six hens (Specimens A-F) the pattern of cpm per gram of digesta of the gut samples from birds A and E (Table 11) was that eXpected from the characteristic defeca- tion patterns (Figure 1). The pattern from birds B and C, however, was the opposite of that eXpected. Birds C and F had more material in their intestines than the other birds and apparently the Cr-51 dose remained in the anterior part of their tracts longer (Table 11). Bird D regurgitated a small amount of labeled material as it was being sacrificed. 62 Table 10. Cpm per gram of digesta** from various segments of the pheasant GI tract after ingestion of a continuous-dose of Cr-Sl as determined by autopsy, Michigan State University, 1966 and 1967 Organ or Tract Segment Bird F—II Bird S—I Average Cpm/Gm of Diet 106 152 Proventriculus . . . . . . . * empty Gizzard . . . . . . . . . . * 140 * 163 Duodenum . . . . . . . . . . * * * .90 * * Small intestine (10-12 cm segment) . . . . . * 132 * 159 * 265 49 278 60 192 + * Ceca . . . . . . . . . . . . 429 431 380 246 Large intestine . . . . . . . 248 * 285 + Cloaca . . . . . . . . . . . 251 * *No detectable level of radioactivity **Where the diet contains a uniform concentration of Cr-51, the increase in Cpm per gram of digesta is directly related to the degree of absorption. + = No sample taken. 63 .mHQEmm oz** .ooHHHx CoCB HMHHoumE ooHoQMH meow ooumuHmHCmmH UHHme mm.0 mm.hm 00.0 00.0 00.0 00.0 CoHou 00.0 NN.0 H¢.m 00.0 00.0 00.0 moon Hmuoe as es 00.0 00.0 00.0 00.0 moCoCH 0mI0¢ «0.m mm.mH 00.0 00.0 00.0 00.0 meUCH oelom 0H.0 HH.m SH.0 m0.0 00.0 00.0 woCUCH 0mI0N m¢.N em.0 0m.m no.0 00.0 00.0 moCOCH 0NI0H >0.H 00.0 mm.H mm.0 N0.H mm.0 moCUCH 0HI0 uoCHumouCH HHmEm gH.H SN.0 0m.0 0m.0 mh.0 mm.n EdCooosn Nm.H m0.H mv.0 no.0 mN.H mH.¢H UHMNNHO mm.m mN.0 m0.H 00.0 0¢.m mm.H mSHCUHHuCo>0Hm 00.0 00.0 m0.> oo.N Nm.mH m0.H osmMCQOmo QOHUIumom >0.m 0H.0 mN.NH Nm.MH mH.HN HH.H mono oo.m oo.o se.oH om.H em.s oo.o mammnmomm Convimnm .CHE mvH .CHE HNH .CHE Hm .CHE 00 .CHE Hm .CHE SH uCoEmom Ho Cmmno "Houmm ooHHHx mouHQ How Cmmuo Como CH UCSOM omoo HmCHmHuo mo ommuCooHom , som.mH www.mH amm.MH ems.aH mme.om mHH.eH leave mmon mo munm m 33 m Tim ...C 6.5m o ofim m 33 C 33 somH cam eemH .suam IHo>HCD mumum CmmHCUHS ..E.m meuNH usonm um cow HmIHO mo mmOUIonCHm o no CoHpmmmCH mCH3OHHom mHm>HouCH um Coxou ouo3 moHQEmm .uoHU uoHHom Hopooum moxuse m Co mCoxUHCU onEmm me mo muomuu as» CH HmIHU mo COHHSQHHumHQ .HH oHHme 64 Since the Cr-51 concentration in its gizzard was lower than that in its small intestine, the regurgitated material could have come all the way from the gizzard. This would explain a higher Cr-Sl level in the crop and esophagus of this bird as compared to birds killed earlier. The general pattern that was expected was observed. The labeled digesta were found further along the tract in birds which were killed longest after ingestion of the Cr-Sl dose. A high percent— age of the dose was not recovered because an effort was made to avoid scraping the gut walls, hence much digesta was left in each segment of the tract. Further studies of the distribution of food labeled in this fashion would be desirable. As an incidental observation, the lengths of the various portions of the pheasant alimentary tract were deter- mined during each autopsy. The averages for four pheasants are: Entire tract from anterior end of the proventriculus to the anus . . . . . . . . . . 109.0 cm Proventriculus . . . . . . . . . 3.5 cm Gizzard . . . . . . . . . . . . . 4.5 cm Small intestine . . . . . . . . . 88.3 cm Large intestine . . . . . . . . . 9.3 cm Each cecum . . . . . . . . . . . 14.3 cm Cloaca . . . . . . . . . . . . . .3.4 cm 65 Energy Budget Using information on the amount of food eaten and metabolized one can construct an energy budget for an animal. The budget for the three diets with bird F-I in the final comparative trials was: Average Number of Turkey Breeder ‘Whglg Caloriespper Day Pellets Chokeberry gpgp Ingested 207,206 112,913 201,002 Metabolizable 87,335 39,917 55,772 Excreted 119,871 72,996 145,230 The average calories ingested per day was determined by multiplying the average grams eaten per day times the calories per gram of food. Determination of the average calories of metabolizable energy obtained per day has been described above. The average calories excreted per day was taken to be the difference between the average calories ingested per day and the average calories of metabolizable energy obtained per day. CONCLUS ION Evaluation of Cr—Sl Used in the Ratio Method with Pheasants Previous investigators have concluded that the use of chromic oxide in the ratio technique for determining feed digestibility was satisfactorily comparable with (Kane gp_al., 1950; Schurch §£_31., 1950; Davis g£_gl., 1958; and Elam g£_gl., 1962) or superior to (Dansky and Hill, 1952; and Sibbald gp_§l., 1960) the total collection method. Unfortu- nately, results with Cr-51 in the present study do not per- mit a similar conclusion. So far as is known, radioactive chromium should react physiologically like stable chromium. Furthermore, the identical continuous-dose procedures used in this study were also applied in a white-tailed deer study in this labo— ratory during the same period with complete success (Mautz and Petrides, 1967). As has been shown, the average metabolizability coefficient determined by the Cr-Sl indicator method was about 10 percent lower than that obtained by the total col- lection method. The coefficients obtained by the ratio method were not only lower but were more variable (standard deviation = 4.324) than those obtained by the total 66 67 collection method (standard deviation = 2.121). The metab- olizability coefficients for bird F-I in the controlled environment on the standard diet, for example, varied from 49.28 to 62.31 percent. The ratio technique employing Cr-51, therefore, is not considered valid for determining metaboliz— ability coefficients in pheasants. At the present time there is no explanation for the difference in the metaboliz— ability coefficients obtained by the two methods. The continuous-dose feeding trial is of value in comparing daytime to nighttime digestibilities of feeds, and in comparing digestibility of foods receiving cecal diges- tion to foods which do not. It is hoped that the Cr-51 indicator method can be modified and improved in the future to make it as useful for determining metabolizability as it is for determining pas- sage rates. There should be further efforts to resolve the disagreement between metabolizability coefficients as deter- mined by the total collection and ratio methods. LITERATURE CITED Bergeim, O. 1926. Intestinal chemistry IV. A method for the study of food utilization or digestibility. J. Biol. Chem. 70:29-33. Border, J. R., L. E. Harris, and J. E. Butcher. 1963. Study of the quantitative fecal recovery of chromic oxide when administered to sheep as a component of paper. J. Anim. 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