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JOHN A. MARCHELLO and WILLIAM H. HALE Nutrition and Management Aspects of Ruminant Animals Related to Reduction of Fat Content in Meat and Milk As knowledge in the field of animal nutrition increased and as the feedlot industry developed, more and more high-concentrate foodstuffs were incorporated into ruminant rations. This was largely due to the avail- ability of low-cost feed grains, which significantly improved efficiency and led to increased monetary returns to the production units while providing animal products, primarily meat and milk, that possessed very high consumer acceptability. As the affluence of the consumer increased, the demand for these high-quality animal products increased, with the result that our entire animal production system is geared to providing these products. Because of the shortage of feed-grain supplies, a management system that requires less grain input for feeding to ruminant animals must be considered. It must be efficient and must provide products that have high consumer acceptability. For many years, our marketing scheme for meat and milk has been based largely on the fat content of these products, because this was a good indication of high quality. A carcass graded Choice must possess a specified amount of intramuscular fat. Many times the result of this requirement is that carcasses graded Choice have substantial amounts of subcutaneous waste fat. Actually, all that is necessary is a small amount of surface fat enough to protect the carcasses during handling, storage, and cooking. Since its inception, the milk-marketing system has been based on the fat content of the milk. Therefore, any management procedure that 101

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102 MARCHELLO AND HALE changes the fat content of milk directly influences the economics of the marketing system. This chapter will present a review of some of the research that has been conducted to determine the effect of nutritional practices and management systems on the composition of carcasses and milk. These remarks will be concerned primarily with efforts to control fat content and with how these efforts affect consumers' acceptance of meat and milk. As early as 1920, researchers were concerned with the composition of gain in ruminant animals. Haecker (1920) designed a study to de- termine the composition of gain from 47 kg to various weights up to 685 kg (Table 1 ) . The initial weight gain of 226 kg was predominantly water (59%~; fat and protein increased about equally (17.2% and 19.3% ). If the total gain from 47 to 458 kg is considered, fat content accounts for a third of the gain in weight. As the final animal weight increased to 685 kg, fat accounted for about 40% of the gain. In a similar study, Moulton et al. (1922) evaluated the composition of gain from birth to 48 months of age. Cattle on three nutritional regimes were considered: full-fed, fed for growth, and limited-fed (Table 21. As the age of the animal increased, fat accounted for a greater percentage of the gain in weight, regardless of nutritional regime. The composition of the increase from birth to 3 months was only 5% fat in the young, thin calf and had an energy content of only 1,734 kcal per kilogram of gain. The composition of the increase from birth to 48 months was about 50% fat in the finished steer and had an energy value in excess of 5,000 kcal per kilogram. When the cattle were fed for limited growth or for minimal growth, the weight gains were primarily increases in water. The contributions of fat and protein to gain in these cattle were similar and increased with advancing age; each accounted for about 20% of the gain from birth to 48 months of age in the two groups of cattle. Wanderstock and Miller (1948) evaluated the influences of five man- agement systems on the carcass composition of fed steers (Table 31. TABLE 1 Composition of Gain in Cattle a From To Water Fat Protein (kg) (kg) (%) (%) (%) 47 273 59.1 17.2 19.3 47 458 49.9 29.4 16.8 47 642 45.9 34.8 15.9 52 685 41.3 40.2 15.4 a Adapted from Haecker (1920) .

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Nutrition and Management Aspects of Ruminant Animals 103 TABLE 2 Percentage of Fat in Cattle of Various Weights on Three Nutritional Regimes e Percentage of Fat, by Nutritional Regime Fed for Limited Age (months) Full-Fed Growth Fed 3 12.8 10.2 5.1 8 19.4 22.7 13.2 11 24.4 17.9 16.4 18 30.0 16.3 11.5 40 48.3 22.2 1 1.4 48 45.8 26.7 18.6 {b SOURCE: Adapted from Moulton et al (1922). These researchers used the 9-10-11 rib cut to establish the physical composition of the steers. Large differences in total fat content were noted among the groups on the various nutritional regimes, even though the cattle were fed to similar weights before slaughter. Carcasses from the pasture-fed (no grain) cattle had the least amount of fat and graded the lowest. Cattle fed on pasture for a short time and then full-fed yielded carcasses that were leaner than those of cattle on the other nutritional regimes, with the exception of the pasture-fed cattle. On the basis of palatability studies, the investigators concluded that beef produced by feeding grain on pasture, after pasturing, or after feeding in drylot was more acceptable to the consumer than that produced by finishing on pasture alone. Meat cuts from the pasture- only cattle were significantly less desirable in palatability and in overall appearance than cuts from the other cattle. TABLE 3 Physical Analyses Data of the 9-10-11 Rib Cut of Cattle under Five Management Schemes a Treatment b Trait Lot 1 Lot 2 Lot 3 Lot 4 Totallean (%) 47.1 52.8 52.4 59.5 52.5 External fat (% ) 12.5 10.8 9.7 5.4 11.0 Total fat (% ) 35.4 28.7 27.7 17.6 30~5 Carcass grade c 12.6 11.6 9.1 8.7 10.6 a Adapted from Wanderstock and Miller (1948). b treatments: Lot 1, full-fed in drylot; Lot 2, full-fed ground corn on pasture; Lot 3, grazed on pasture for short time, then full-fed in drylot; Lot 4, grazed on pasture only; Lot 5, grazed on pasture full season, then full-fed in drylot. c 13 = average Choice; 10 = average Good; 7 = average Standard

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104 MARCHELLO AND HALE Jacobson and Fenton (1956) observed the effects of three feeding levels and animal age (30-80 weeks) on the quality of beef from Holstein cattle. The three levels of nutrition represented 60%, 100%, and 160% of the amounts of total digestible nutrients according to the upper limits of Morrison's (1949) standards for growing dairy heifers. Small differences in the amounts of intramuscular fat were noted as the nutrition level increased (Table 41. About 3% of intramuscular fat for the cattle receiving the high level of nutrition approaches the lower limit of what is observed in a beef carcass graded Choice by today7s standards. The data in Table 4 strongly suggest that the levels of nutrition had no effect on the palatability of the meat coming from these cattle. Animal age had a much greater effect on palatability than nutritional level. Ages considered were 32, 48, 64, and 80 weeks. Animals 32-48 weeks of age at slaughter had similar levels of intramuscular fat ( 1 .2~o ); older cattle had twice as much. In general, Jacobson and Fenton (1956) concluded that the fat content and shear values increased with animal age. Scores for aroma, flavor, juiciness, and tenderness decreased after 48 weeks of age, re- gardless of nutritional regime. Guenther et al. (1965) used half-sib Hereford steer calves (225 kg) to determine the effect of plane of nutrition on growth and development from weaning to slaughter weight. The design permitted comparison on both an age- and weight-constant basis. The design of the experiment was as follows: Lot W Calves were slaughtered at weaning time. Lot HI Calves were fed on a high plane of nutrition to 125 kg post- weaning gain, then removed from test and slaughtered. TABLE 4 Levels of Nutrition for Beef Cattle: Their Effect on Fat Content of Muscle and Palatability ~ Palatability Evaluation Level of Fat Nutrition ~( % ) Aroma c Flavor c Juiciness c Shear Value d Low 0.8 6.8 6.7 7.0 6.4 Medium 1.8 6.6 7.3 7.5 7.7 High 2.7 6.7 7.3 7.3 6.4 a Adapted from Jacobson and Fenton (1956). b Low, medium, and high represent, respectively, 60%, 100%, and 160% of the amounts of total digestible nutrients recommended by Morrison (1949). c Ten-point scale with 10 being most acceptable. Kilograms of force to shear a core 2.5 cm in diameter. The higher value is less tender.

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Nutrition and Management Aspects of Ruminant Animals 105 Lot Ma- Calves were fed on a moderate plane of nutrition. They were removed from test and slaughtered at the same time as the H. calves (age-constant basis) . Lot H2-Calves were fed on a high plane to 205 kg postweaning gain, then slaughtered. Lot M2 Calves were fed on a moderate plane. They were removed from test and slaughtered at an age-constant basis to the H2 calves. Lot Ma-Calves were fed on a moderate plane to 205 kg postweaning gain. They were slaughtered on a weight-constant basis with the He calves. Feed requirements per unit of gain were largest during the initial phase of the feedlot period and greatly favored the high-level steers over the age-constant moderate group of steers. On a weight-constant basis, however, little difference was noted in feed requirements. Carcass grade also favored the high-level cattle. Fat accumulation was most rapid during the latter half of the feed- ing period and showed a sharp increase after lean production began to subside. Thus the lean: fat ratio became smaller and less desirable as the feedlot period was extended past this point. Experimental steers weighed about 355 kg and were almost 11 months old at this time. Com- parisons of the influence of nutritional treatment on fat content of certain carcass wholesale cuts are made in Figure 1. Sizable differences were noted for some of these cuts. Fat-deposition trends were estab- lished for each wholesale cut although considerable variation existed between cuts. Lofgreen (1968) determined the body composition of cattle follow- ing the application of varying planes of nutrition in both feeder calves and yearling steers. The following design was used: ~t Low-energy ration (20% concentrate) for 273 days. LEH Low energy for 182 days and high energy (90% concentrate) for 91 days. EMH Low energy for 91 days, medium energy (55% concentrate) for 91 days, and high energy for 91 days. HML High energy for 91 days, medium energy for 91 days, and low energy for 91 days. HHL High energy for 182 days and low energy for 91 days. HHH High energy for 273 days. The results of this experiment are given in Table 5. Increasing the level of concentrate resulted in carcasses that carried greater amounts

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l o - 7.5 ySO #: O ~ 1 . W H'M'H2M2M3 106 MARCHELLO AND HALE CHUCK RIB LOIN ROUND W H. Ml H2M2M3 W H. M, H2M2M3 TREATMENTS W H' M'H2M2M3 FIGURE 1 Effect of plane of nutrition on deposition of fat in certain wholesale cuts of beef. Treatments: W. slaughtered at weaning time; H1, high plane for 125 kg of gain; M1, moderate plane and slaughtered at the same time as H1; H., high plane for 205 kg of gain; M-, moderate plane and slaughtered at same time as He; Me, moderate plane for 205 kg of gain. (Adapted from Guenther et Cal., 1965) of body fat. This effect was more pronounced in yearling cattle than in calves. Differences in marbling score (intramuscular fat) were small and apparently not influenced to a large degree by nutrition in either age group. Marbling values observed would have permitted most of the carcasses to be considered for the Choice grade as determined by current federal grading standards. Therefore, meat cuts from these cattle could be presumed to have high consumer acceptability, regard- less of nutritional regime. However, Zinn et al. (1970) found marbling scores and carcass grades to increase significantly (p<0.05) up to 240 days on feed. Steers reached a given grade 30-60 days earlier than heifers, even though deposition of intramuscular fat was similar between sexes. The data indicated that steers and heifers deposited intramuscular fat at a similar rate and that deposition of intramuscular fat is not a continuous process but proceeds in stages at intervals of 60-90 days. The effect of nutritional level imposed from birth to 8 months of age on subsequent development of full-fed beef calves was investigated by Stuedemann et al. (19681. Each of five groups of calves was subjected to one of the following nutritional levels: very restricted, restricted,

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Nutrition and Management Aspects of Ruminant Animals 107 .= o ~ ~ I ~ ~ ~ _ l 1 i - 1 _ I ~ o U. U' Cal Ct Ct V m Cat o v Ct o o ._ ._ 50 Can o Ct - o C) at m a Cal 0 _ C5 in. CO Ct ~0 U3 - Ct U. Ct au Lo SO ~ ~ O a U. U3 ,, C) .= ~ 3 ~ .= 0 ~ ~ 1~ ~ ~ _ 04 _ ~ "D ~ s~ ~ ce 0 c' u, ~ ^ u, U3 ,= c' .= _- ~ ~ 0 c: 3 ~ ct ~ ~ 0 ~ 0 ~ . . . . r~ ~ t- ~ ~ c~ . . . . r~ 00 ~ c~ . . . .. - ~ ~ ~ ~ ~ ~ ~ o ~o - ~ - l oo ~ ~ ~ ~ ~ c~ ~ ~ ~ ~ ~ . . . . ~ ~ oo ~ ~ o ~ ~ - ~ ~ ~ ~ ~ o ~ ~ o ~ ~ ~ . . . ~ . ~D \0 ~ ~ ~ oo ~ oo . . . . . . _ ~ _ - _1 ~ _ kD =' - ~ ~ ~ tn ce ~ c, ~ 3 o~ o _~ - _ oo c~s o .. ~ O C, U, ~ o ._ Ct oe CJ .= . ~ U, ;^ Ct o~ o C~ - - C) o V~ _' o - C5 ~C CJ ~; ._ C) ~C . ~ ~3 Cd ~3 o' o C) c: Ct _ ~ C o s os .= U, 11 ~o - ~oo o.^ _C) Ct_ C. ~, o C U, - C~ o CJ ~ 11 C) _ o ~c U) ~ 11 o ~, _ ~ - ~n C, ~;

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10 9 8 7 6 C~ 5 4 3 2 108 MARCHELLO AND HALE normal, high, and very high. These levels were based on milk pro- duction of the dam and additional supplementation. In those calves slaughtered at 8 months of age, the relative amounts of lean, fat, and bone tissue produced were directly influenced by the level of nutrition imposed. As the level of nutrition decreased, significantly (p<0.05), less tissue was produced. The relative retardation of growth was greatest in fat tissue, followed by lean and bone (Figure 21. Differences in the average daily feedlot gains of the calves were not statistically significant. However, calves subjected to the lower planes of nutrition during early life required more days in the feedlot to attain the desired constant market weight. Regardless of nutrition in early life, once the cattle completed the feedlot period at a constant weight, no differences were noted in carcass composition (Figure 21. Results in contrast with these were obtained by Winchester et al. (1967), who conducted a study in which identical twins were used. One member of the pair was restricted in plane of nutrition for periods of 3-6 months; the other was allowed to grow and develop on a normal plane of nutrition. Little difference was observed in the final carcass composition of these calves when they were slaughtered at equal body weights. CHUCK Rl B LOIN ~ ROUND 1 2 3 4 5 1 I. 1 2 3 4 5 1 2 3 4 5 MARKET WT. 8 MO WT. 1 2 3 4 5 TREATMENTS FIGURE 2 Effect of nutritional level imposed from birth to 8 months of age on the amount of fat in the round, rib, loin, and chuck of beef calves slaughtered at 8 months and at a constant market weight. Treatments: 1=very restricted, 2=re- stricted, 3=normal, 4=high, 5=very high. (Adapted from Stuedemann et al., 1968 )

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Nutrition and Management Aspects of Ruminant Animals 109 A similar situation appears to be true for sheep, as revealed by Burton and Reid (19691. Regression coefficients between body com- ponents and body weight are given in Table 6. The composition of the carcasses was not influenced by plane of nutrition when the sheep were evaluated at equal body weights. Berg and Butterfield (1968) reviewed the growth pattern of bovine muscle, fat, and bone and concluded that a high plane of nutrition in- creases the percentage of carcass fat. This conclusion was based on the results presented by Guenther et al. ( 1965), where the differences were not statistically significant. Consequently, Preston (1971) stated that the evidence for such an effect is meager arid that, in fact, there is overwhelming evidence that plane of nutrition has little or no effect on final carcass composition in cattle and sheep at constant weights. Utley et al. (1971) conducted a 3-year study of two systems for finishing beef steers. The purpose was to evaluate the influence of the systems on feedlot performance and carcass merit. One system was designed to make maximum use of harvested and grazed forages; the other was designed to maximize gains by feeding a high-energy finishing diet from weaning time (219 kg) to a slaughter weight of 455 kg. The steers fed the high-energy diet reached market weight, on the average, 153 days sooner than the steers on the roughage system. Dressing per- centages and subcutaneous fat thickness were slightly lower for the forage-fed cattle, but carcass grades were similar for both groups. However, Garrett (1974) found in comparing yearling steers fed 20%, 40%, or 60% alfalfa in the finishing diet that the carcass grades were similar but that the 40% and 60% alfalfa groups had carcasses with about 4% less body fat than the 20% alfalfa group (Table 71. Grain consumption by the steers ore the 60% alfalfa diet was 28% less than those on the 20% alfalfa diet, and steers in the former group required an additional 40 days to reach comparable finishing weights. These results suggest that management systems can be developed that TABLE 6 Regression Coefficients between Body Components (kg) and Empty-Body Weight (kg) of Sheep Receiving Two Energy Levels a Energy Level Water Body Components Fat Protein Ash Energy High 0.357 0.517 0.109 0.018 5.517 Low 0.376 0.498 0.106 0.019 5.344 a SOURCE: Burton and Reid (1969). Courtesy, Journal of Nutrition.

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110 MARCHELLO AND HALE TABLE 7 Response of Heavy Steer Calves Fed Three Levels of Alfalfa a Level of Alfalfa in the Ration Variable 20% 40% 60% Final weight (kg)b 474 486 495 Total gain (kg) 184 195 203 Days on feed 140 161 182 Average daily gain (kg)h 1.3 e 1.2e, f 1.1 Grain in the diet (% ) 71.2 53.3 35.3 Total "rain consumed (kg) 848 803 607 Total carcass fat (% ) 34.0 c 30 3 f 30.1 t Carcass grade c 10.3 10.8 1 1.0 Yield grade ~2.9 3.0 2.8 SOURCE: Garrett (1974) . 7> Correct to dressing percentage of 62. c Carcass grade: 9 = low Good; 10 = average Good; 11-high Good. The lower scores have higher curability percentages. e,t Values on the same line with unlike superscripts differ (p < 0.05). utilize less grain with acceptable feedlot performance, yet produce desirable carcasses with less fat. Hormonal growth stimulants have been effectively used in the live- stock industry for many years to increase weight gains. Marchello et al. (1970) evaluated the influence of some of them on fat deposition in conjunction with seasonal effects (Table 81. None of the stimulants compared were effective in reducing the deposition of subcutaneous or intramuscular fat. However, some of them improved the curability of the carcass, which is surprising since curability is largely dependent on the amount of subcutaneous fat present. Possibly this can be at- tributed to a greater proliferation of muscle growth. The cattle finished in the summer months significantly (p OCR for page 101
Nutrition and Management Aspects of Ruminant Animals 111 TABLE 8 Influence of Season and Hormonal Growth Stimulants on Certain Traits of Beef Carcasses a Fat Intramuscular Thickness Fat Cutability (cm) (%) (%) Summer Control 1.7 19.1 49.0 MGA 1.6 19.4 49.1 Winter Control 1.2 16.5 50.2 b, c MGA 1.3 16.2 49.9 b DES 1.1 17.0 50.7 c Summer Control 1.9 15.9 48.2 ~ MGA 1.8 16.2 48.3 b Synovex-H 1.7 15.6 49.0 b, c Rapigain-1 1.6 15.0 49.6 c Winter Control 1.0 15.5 50.5 MGA 1.0 14.5 50.5 Synovex-H 1.0 15.6 51.0 Rapigain-1 1.0 15.8 50.8 a Adapted from Marchello et al. (1970). b,c Values for each season with unlike superscripts differ significantly (p < 0.05). TABLE 9 Effect of Synovex and Ralgro on Body Composition of Beef Cattle a Body Composition c Slaughter Weight Quality Yield Fat Protein Treatment (lb) Grade b Grade (% ) (% ) Control 1047 1 2.S 2.4 32.4 d 15.0 d Synovex 5 initially No additional 1074 11.9 2.3 29.5 e 15.66 Synovex reimplant 1156 12.3 2.3 29.06 15.7 e Ralgro reimplant 1123 12.2 2.2 29.5 c 15.6 e Ralgro initially No additional 1091 11.8 2.1 29.se l5.6e Synovex reimplant 1096 11.9 2.4 29.se l5.6e Ralgro reimplant 1078 12.1 2.1 3o.o e 15.5 e Synovex S+Ralgro 1105 12.3 2.3 29.0 e 15.7 e a SOURCE: Lofgreen (1974). h 13 = average Choice; 12 = low Choice; 11-high Good. c Determined by specific gravity. die Values within the same column with unlike superscripts differ significantly (p < 0.01).

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i12 MARCHELLO AND HALE different from those presented by alteration of the fat content of fed steers. Differences in the fat content of milk from cows fed typical diets are reflections of the genetics of the animals. A producer is paid for his milk on the basis of fat content, and regulations in most states fix, or at least limit, the lower level of fat in retail whole milk. Thus, any feeding or management system whose purpose is to change the fat content of milk may be undesirable. The chances that a change would be undesirable are increased if the purpose is to lower the fat content. Any desired change in the fat content of retail milk can easily be made by the processor. Fat percentages in milk may be depressed by certain feeding sys- tems for example, feeding finely ground feeds, feeding highly digestible roughages, and high levels of grain feeding (Davis and Brown, 19701. In practice, fat levels in milk are sometimes inadvertently depressed by some change in feeding management, and immediate efforts are made to restore the fat level to normal. The effect of reduction of fat levels in milk due to feeding systems on total milk production over the entire lactation is unknown. In the last 30 years, there has been a marked increase in milk yield per cow. In part, this increase is due to genetic improvement, man- agement, and disease control. The greatest increase is probably due to improved nutrition for the cows. There has been an improvement in the metabolizable energy (ME) of forages, resulting from improvement in harvesting methods, and an increase in the ME intake of the lactating cow as a result of grain feeding. It is possible to meet the energy requirements of cows producing 20 kg or less of milk per day by feeding only good-quality alfalfa hay; however, efficiency of production would be improved by including some concentrate in the feeding system. For cows with the ability to produce 30 kg or more of milk per day, concentrate feeding is essential, because roughage or corn silage diets do not contain sufficient ME to meet the energy requirements of the cows. S UM MARY Alteration of carcass composition of ruminants through nutrition ap- pears possible. However, when the available literature was surveyed, it was apparent that compositional changes are difficult to accomplish without resorting to drastic reduction in energy intake for prolonged periods. Within the practical realm of rations fed to cattle and sheep, plane of nutrition will not alter the gross chemical composition of their carcasses. This is not to say that changes do not occur histologically or in the distribution of carcass constituents.

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Nutrition and Management Aspects of Ruminant Animals 113 In comparing usual nutritional regimes, it is apparent that if the ani- mals are fed to constant final slaughter weight, major differences in carcass composition are eliminated. However, if the ruminants are sub- jected to a prolonged negative energy balance, a carcass is produced with increased fat content if the animals are provided with a marked positive energy balance before slaughter weight is attained. Reduced planes of nutrition that result in compensatory growth when cattle are placed on full feed yield animals with altered body composition for a period of time. However, these animals have carcasses similar in composition to those of full-fed animals once slaughter weight is reached. Apparently, the growth phase of these animals is prolonged until certain body needs are met, then fat accumulation predominates. Animal age plays an important role in body composition. At very young ages, body composition will be predominantly water and protein. As the animals advance in age, fat content will increase at an increasing rate regardless of nutritional regime provided the animals are in positive energy balance. It seems reasonable to assume that reduced nutrition at very young ages would result in altered composition at slaughter weight. However, if a high plane of nutrition is provided as part of the feeding regime, differences in carcass composition are minimal. The season of the year may influence the deposition of fat. This appears to be mediated as a body defense mechanism to cope with ad- verse environmental conditions. High environmental temperatures pro- mote the deposition of large quantities of fat. It is also conceivable that high temperatures would alter fat composition. With the possibility of an indefinite shortage of feed grains, feeding systems must be evaluated with the aim of preserving quality while using less grain. It is conceivable that these systems can be used without sacrificing consumer acceptance of the meat cuts. The data presented in this chapter show that lowering grain levels in finishing diets merely results in lower daily gains with no effect on carcass composition. Ex- periments must be designed to specifically evaluate the effects of reduced grain feeding on economy, production, carcass composition, and palat- ability. Adoption of management systems that use less grain could necessi- tate significant changes in the federal carcass-grading standards. Further- more, for snaky years, packer buyers have selected cattle and sheep for purchase primarily on the basis of grade and dressing percentage. The use of dressing percentage poses a problem, because it promotes the propagation of animals possessing unwanted quantities of waste fat. Alternative procedures must be considered. The United States is probably the only country using an outdated system for marketing ani- mals. The use of a procedure that would reflect the merits of the carcass

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114 MARCHELLO AND HALE seems much more desirable. The adoption of mandatory yield-grading would help alleviate this problem. However, until producers and feeders are compensated for producing cattle and sheep with superior carcasses (more high-quality lean and less fat), the marketing system will con- tinue to price slaughter animals on the same level, regardless of merit. Nutritional and management systems that can alter the fat content of milk are available. However, because of the present pricing system, which is based on fat, it is inadvisable to consider any of these systems; they would result in direct monetary losses to the production unit. Furthermore, fat level in retail milk can be adjusted easily at the processing stage. An alternative system using solids-not-fat as a base seems more realistic. It is not within the scope of this chapter to consider the genetic consti tution of ruminants. The propagation of superior animals with superior genotypes with regard to carcass composition appears to be the most logical procedure to attain the desired end product. This, coupled with proper nutritional regimes, could result in the production of cattle and sheep that provide carcasses that are relatively free of waste fat and possess meat quality that has optimum consumer acceptance. RE FERENCES ~erg, x. r., and R. M. Butterfield. 1968. Growth patterns of bovine muscle, fat and bone. J. Anim. Sci. 27:611. Burton, J. H., and J. T. Reid. 1969. Interrelationships among energy input, body size, age and body composition of sheep. J. Nutr. 97:517. Davis, C. L., and R. E. Brown. 1970. Physiology of Digestion and Metabolism in the Ruminant. Oriel Press Ltd., Newcastle, England. 454 pp. Garrett, W. N. 1974. Influence of roughage quality on the performance of feed- lot cattle. 13th Annul Calif. Feeders Day Rep., p. 51. Guenther, J. J., D. H. Bushman, L. S. Pope, and R. D. Morrison. 1965. Growth and development of the major carcass tissues in beef calves from weaning to slaughter weight, with reference to the effect of plane of nutrition. J. Anim. Sci. 24:1184. Haecker, T. L. 1920. Investigations in beef production. Minn. Agric. Exp. Stn. Bull. 193. Jacobson, M., and F. Fenton. 1956. Effects of three levels of nutrition and age of animal on the quality of beef. I. Palatability, cooking data, moisture, fat, and nitrogen. Food Res. 21:415. Lofgreen, G. P. 1968. The effect of nutrition on carcass characteristics. 4th Annul Ariz. Feeds Elanco Semin., p. 7. Lofgreen, G. P. 1974. Effect of Synovex S and Ralgro on performance and body composition. 13th Annul Calif. Feeders Day Rep., p. 4. Marchello, J. A., D. E. Ray, and W. H. Hale. 1970. Carcass characteristics of beef cattle as influenced by season, sex and hormonal growth stimulants. J. Anim. Sci. 31:690.

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Nutrition and Management Aspects of Ruminant Animals 115 Morrison, F. B. 1949. Feeds and Feeding, 21st ed. The Morrison Publishing Com- pany, Ithaca, N.Y. Moulton, C. R., P. F. Trowbridge, and L. D. Haigh. 1922. Studies in animal nutri- tion. II. Changes in proportion of carcass and offal on different planes of nutri- tion. Mo. Agric. Exp. Stn. Res. Bull. 55. Preston, R. L. 1971. Effects of nutrition on the body composition of cattle and sheep. Ga. Nutr. Conf. Feed Ind., p. 26. Stuedemann, J. A., J. J. Guenther, S. A. Ewing, R. D. Morrison, and G. V. Odell. 1968. Effect of nutritional level imposed from birth to eight months of age on subsequent growth and development patterns of full-fed beef calves. J. Anim. Sci. 27:234. Utley, P. R., R. B. Moss, and W. C. McCormick. 1972. Systems of management for finishing beef steers. Univ. Ga. Call. Agric. Exp. Stn. Res. Rep. 128. Wanderstock, J. J., and J. I. Miller. 1948. Quality and palatability of beef as affected by method of feeding and carcass grade. J. Food Res. 13:291. Winchester, C. F., R. E. Davis, and R. L. Hiner. 1967. Malnutrition of young cattle: Effect on feed utilization, eventual body size, and meat quality. USDA Tech. Bull. 1374. Finn, D. W., R. M. Durham, and H. 13. Hedrick. 1970. Feedlot and carcass grade characteristics of steers and heifers as influenced by days on feed. J. Anim. Sci. 31:307.