CATTLE PRODUCTION SYSTEMS TO MEET

Transcription

1 CATTLE PRODUCTION SYSTEMS TO MEET FUTURE CONSUMER DEMANDS 1 M. E. Dikeman 2 Kansas State University, Manhattan Summary In recent years beef cattle production has not been routinely profitable because of continuing increases in production costs and decreases in per capita consumption of beef. Consumers appear to be demanding that beef be competitively priced with other animal protein sources and that its composition, or fat content, be modified to result in optimum nutritional value. Consumers will continue to demand highly palatable beef products. Reestablishing consumer confidence and demand for beef will be important for profitability in the industry. Because it is more costly to produce fat than muscle, production costs could be reduced significantly by marketing cattle with less fat. The beef cattle industry is challenged to synchronize the diversity in genetic resources with production resources and environments. Production is optimized when breeding female genotypes are crossed with sire genotypes. Breeding females should be crosses of Bos indicus and Bos taurus breeds where the environment is suitable. The value of cattle as harvestors of roughage will continue to be important, and the potential of the ruminant digestive system must be fully utilized. Feed grains will remain the primary energy source for finishing cattle, but shorter finishing periods will be utilized for conventional breeds of cattle. Accelerated, or highly intensive feeding systems will be utilized for faster growing, more muscular genotypes. The industry must decrease 1 Paper presented at the symposium on "Red Meat Production and Processing Systems for the 21st Century" at the 75th Annu. Meet. of the Amer. Soc. Anita. Sci., Washington State Univ., Pullman, July 29, Contribution No J, Dept. of Anita. Sci. and Ind., Kansas Agr. Exp. Sta., Manhattan Received January 24, Accepted June 25, the emphasis on "feeding quality into beef" and accept the large volume of research that shows a weak relationship between marbling and palatability of beef from young, grain finished cattle. The compositional end point at which production efficiency, processing efficiency, optimum beef nutrition and sensory traits are optimized is in the early stage of fattening. Cattle production systems must assume the role of efficiently producing muscle with some fat included. Meat processing technology must assume a greater role in assuring consumer acceptance of beef in the future. (Key Words: Beef Cattle, Production Systems, Consumer Demands, Meat.) Introduction Recent advances in nutrition, management, reproduction, genetics, animal breeding and meat processing have been significant. However, they have not been significant enough to make beef cattle production and beef processing routinely profitable. This is due, in large part, to the overproduction of animal fat that results from current production, grading, processing and marketing practices. Because it is more costly to produce fat than muscle, it is inefficient to feed cattle until they have 30 to 35% carcass chemical fat, which is typical of many USDA Choice, yield grade 3 cattle. In addition, reduced consumer purchasing power and changes in consumer demands and attitudes about beef have created significant pressure on the beef cattle production and processing industries. This has occurred while costs of production, particularly capital and energy, have increased dramatically. Consequently, beef is not very competitive with other protein sources in price/unit of protein. At the same time, beef lost popularity with many consumers from 1976 to 1982 because of diet-health controversies and concern about nutrition and calories of beef with excess fat JOURNAL OF ANIMAL SCIENCE, Vol. 59, No. 6, 1984

2 1632 DIKEMAN To increase efficiency of beef production, additional advances must occur in genetics and animal breeding, management, nutrition, reproduetion, growth biology, marketing, meat processing and meat merchandising. In a recent report by the National Cattlemen's Association (NCA, 1982), it was noted that there will be a future information explosion that will force cattle producers to change their production and marketing systems. Essential in those changes will be a significant reduction in the amount of fat in market cattle. Without the reduction of fat in market cattle, these advances may not signifcantly improve the competitive situation of beef. Consumer Demands for Beef Few industries or businesses of any kind survive over time without satisfied customers for their products. The beef industry is fortunate that its primary end product is enjoyed by consumers as well as being very nutritional. However, the beef industry's production, processing and merchandising systems are much more oriented to producing beef that is enjoyed by consumers than they are to producing a product that is economical and optimum in nutrition. There are strong indications that consumers are not satisfied with the nutritional value and price of beef now being produced. The basic production system now utilized results in excess carcass fat and a significant portion is not removed when beef is merchandised. This excess fat dilutes the protein, mineral and water soluble vitamin content of beef and increases its caloric content. Since the early 1970's many public opinion and economic factors have been working against beef consumption. Per capita consumption of beef peaked in 1976 at 42.8 kg (retail weight), declined to 34.7 kg in 1980 and has increased slightly since then. Beef consumption has been linked to a number of chronic or degenerative diseases, and the saturated fat in beef has been the dietary component indicated as the major culprit. Publications of AHA (1978), U.S. Senate (1977) and NRC (1982) have been prominent in creating a public perception that lower consumption of animal fats will be effective in reducing the incidence of these diseases and, thereby, increasing life expectancy (Harper, 1982). Whether or not these allegations regarding animal fat are scientifically valid, the reality of consumer perception has had its impact. Quite apart from the emphasis on relationships between diet and chronic and degenerative diseases, there also is wide-spread emphasis on weight reduction as a measure for improving health. There is little controversy over the high prevalence of overweight and obesity in the United States, and little doubt about the health hazard of being excessively overweight (HarL~er, 1982). Because fat is a rich rouce of calories, it seems likely that consumers will demand beef with less fat. Harper (1982) stated that inaccurate public perceptions about relationships between diet and health, and particularly about diet and disease, have been created by widespread publicity in the media of misleading, inaccurate and incomplete information. Harper (1982) noted that there has been no "epidemic" of either heart disease or of cancer in the last 40 yr. He further states that age-adjusted death rates from cardiovascular diseases were higher during the first 40 yr of this century than they are now. The saturated fat content in the diet has remained relatively constant during the last 30 yr, whereas the unsaturated fat content of the diet has increased over the last 30 yr, but not enough to have much effect on serum cholesterol concentrations (Harper, 1982). Much information on diet-health relationships has been provided by public health advocates who accept evidence of association, rather than cause and effect relationships, as an adequate basis for public policy proposals. Public perceptions do not change rapidly, so emphasis on low fat diets, including low fat beef, is likely to continue. Because of public perception and the need for many people to lower calorie intake, beef should be merchandised with less fat. Its positive nutritional attributes of being high in quality protein and a rich source of vitamins and essential minerals should be promoted. Aside from diet-health controversies concerning beef, consumers have purchased alternative protein sources, such as dairy, poultry and fish products, because of a lower unit price. A report by NCA (1982) stated that in the 1950's retail chicken price was about 80% of retail beef price, but in the 1980's chicken price is only about 30% of beef price. The production of excess fat by current feeding and marketing practices substantially increases costs of production and places beef in a noncompetitive price situation with these other protein sources. Thomas B. Smith, Community Nutrition In-

3 FUTURE DEMANDS ON CATTLE PRODUCTION SYSTEMS 1633 stitute, stated at the Iowa State University Beef Grading Conference (Zmolek et al., 1981) that most consumers want leaner beef, with cost being the primary reason, and diet-health concerns a close second. The fact that beef is the preferred meat of consumers has probably been a major factor in keeping demand as high as it is. Consumer demands do create a difficult contradiction with which to deal. They want to enjoy the ultimate in meat sensory attributes that have been associated with the highly marbled Choice and Prime grades; however, they do not want beef to be fat. They have resisted proposed grade changes that prescribe a reduction in marbling levels for certain grades. Furthermore, they demand low-fat chuck, round and ground beef items, but desire rib and loin cuts that come from Choice and Prime beef. In addition, the consumption of ground beef has increased dramatically, which results in less of the carcass being consumed as roasts, steaks and other cuts. Beef production, processing and merchandising systems must be tailored to meet consumer demands for palatability and nutrition. Although consumer demands may be somewhat unpredictable and inconsistent, the beef industry must optimize the nutritional value and palatability traits of beef as a food. Perhaps as important, these systems must become much more efficient in order for beef to be more competitive with other protein sources. Fortunately, the demand for beef with less fat is compatible with increasing efficiency of beef production. Cow Efficiency At least 65% of the nutrients used for beef cattle production in the U.S. is required to produce calves to weaning age (Gregory, 1972). Thus, improvements in production efficiency during the reproduction segment of the beef production cycle would have a major impact on the total efficiency of producing beef. Under certain range production systems, the opportunity for increasing efficiency through improved nutrition, management and synchronization of genetic resources with the environment may be limited. A significant proportion of U.S. cow-calf production occurs in range areas where the synchronization of genetic resources with the environment may be the primary factor affecting productivity. Yet, there is a definite lack of research on range management, nutrition and synchronization of genetic resources to the environment. Until such research is conducted, perhaps the greatest opportunity for increasing efficiency in production of weanling calves exists where pasture and forage resources can be increased through management, and where various crop residues can be used to maintain breeding females. In addition, there is greater flexibility to modify production systems to meet shifts in market demands. Numerous studies have indicated that 75 to 80% of the nutrients consumed by beef cow herds are used for maintenance and only 20 to 25% for production. Therefore, the goal of diluting maintenance costs by marketing more weight per cow is a plausible one. Increasing cow productivity is one method of seeking to meet that goal. Genetic resources are available for increasing milk production, growth rate, size, muscling and reduced body fat. Provided that the nutritive and climatic environment are adequate to support reproductive function, calf weaning weights can be increased greatly when large and(or) heavy-milking genotypes are utilized. In evaluating the efficiency of different cow genotypes, both feed and nonfeed costs must be considered. In recent years, nonfeed costs have been extremely important in determining profitability of cow-calf operations. Differences in efficiency of energy utilization in producing a unit of weaned calf weight are generally independent of cow weight, provided the nutritive environment is adequate to support reproductive function. Numerous studies have shown essentially no efficiency advantage in energy required/unit of weaned calf weight for larger and(or) heavier-milking genotypes (Holloway et al., 1975a,b; Klosterman and Parker, 1976; Marshal1 et al., 1976; Bowden, 1981). Other studies have been conducted in which efficiency was measured as feed energy consumed per unit of retail product produced. Klosterman and Parker (1976) found no difference in total digestible nutrients (TDN) per unit of edible portion among four genetically diverse breeding groups. Brown and Dinkel (1978) found similar results in studying three breed groups. Cundiff (1983) reported no meaningful differences among four groups of F1 crossbred cows in metabolizable energy required per unit of trimmed retail product.

4 1634 DIKEMAN Thus, there essentially is no difference among genotypes in energetic efficiency. When economic efficiency rather than energetic efficiency was measured by Farris et al. (1981) for nine genotypes differing in size and milk production, heavier milking cows were more profitable than lighter milking cows. However, when calves were fed to slaughter, the lightest milkers tended to be most profitable. Large cows were generally the most profitable regardless whether calves were marketed at weaning or fed to slaughter weights. Many of the nonfeed costs were on a per head basis, which favors fewer, larger, heavier milking COWS. From these results it seems that increasing cow size and milk production is not very beneficial when efficiency is calculated as energy required per unit of weaned calf weight or per unit of retail product produced. On the other hand, when economic efficiency is measured, large, heavy milking cows generally have an advantage. Certainly, profitability must be a major consideration in any production system. Even so, increasing cow size and milk production may not be as beneficial to increasing efficiency of beef production as other methods. Crossbreeding Systems Crossbreeding improves efficiency 10 to 25% and must be a part of any economical production system, even for cow herds of less than 50 head. The cumulative effects of heterosis on traits that contribute to weight of calf weaned per cow exposed to breeding appear to be approximately 50% for crosses between Bos taurus and Bos indicus breeds of cattle (Cartwright et al., 1964; Koger et al., 1975). This is approximately twice as great as the percentage of heterosis (approximately 23%) for crosses among breeds of Bos taurus cattle (Gregory et al., 1965; Wiltbank et al., 1967; Cundiff et al., 1974a,b). Furthermore, these results show that 60% or more of this heterosis is the result of heterosis effects on maternal characteristics. Thus, crossbreeding systems that include a high percentage of the reproducing female population as crossbreds of Bos indicus and Bos taurus breeds are generally favored, with 25 to 50% Bos indicus breeding in females being the optimum percentage. Notter et al. (1979) concluded that beef cattle production is optimized when breeding females are chosen for fertility, mothering ability and foraging ability in the environment in which they are placed and then are mated to terminal sire breeds selected for growth rate, muscling and reduced body fat. This type of production system requires more intensified management because of the more complicated crossbreeding systems that must be utilized to maintain maternal traits of breeding females and to avoid excessive calving difficulties associated with mating larger, more muscular sire genotypes to first and second calf maternal genotypes. Thus, first, second and perhaps third matings of these females should be to a sire from a maternal breed noted for calving ease. Then, the mature females are mated to terminal sire breeds, and both male and female offspring are fed for slaughter. A three-breed rotation, terminal-sire crossbreeding system outlined by Gregory and Cundiff (1980) results in an approximate 4% increase in weight of calf weaned compared with a three-breed rotation crossbreeding system. Advantages in lower cost per unit of retail product would add to the superior weaned calf efficiency of a three-breed rotation, terminal-sire crossbreeding system because of the growth rate, feed efficiency and carcass cutability advantages of the terminal-sire calves produced. Morris and Wilton (1976) concluded that system efficiency (evaluated as gross farm margins) was greatest when the differences in size between the sire and dam breed were maximum. Dickerson (1970) indicated that the greatest genetic opportunity for reducing costs lies in increasing total product per female with minimum increase in metabolic size, and in nonfeed costs per female. Smith (1976) reported advantages in cost per unit of retail product for larger, faster growing sire breeds mated to Angus and Hereford females, even when first and second calf females were mated to terminal sire breeds and significant dystocia problems and increased calf mortality resulted. These economic advantages should be even greater when a three-breed rotation, terminal sire crossbreeding system is utilized and the excessive calving problems are eliminated by only mating mature females to terminal sires. This program exploits complementarity, heterosis and the opportunity to synchronize genetic resources with market requirements and feed resources. It is the most effective means of managing trade-offs that result from genetic antagonisms (Cundiff,

5 FUTURE DEMANDS ON CATTLE PRODUCTION SYSTEMS ). In such a system, approximately twothirds of the calves marketed are by terminal sires and one-third by maternal sires in the rotation. The additional heterosis (where the environment permits) that can be obtained from Bos taurus and Bos indicus crosses in the rotation should be utilized. Artificial insemination is increasingly recognized as a tool for genetic improvement, but is used on a limited basis by the beef cattle industry. Where feasible, cattle producers should consider implementation of this valuable management tool, particularly with recent developments in estrous synchronization. Successful estrous synchronization compounds allow cattlemen to artificially inseminate a very high percentage of the cow herd within a 5 d period and to reinseminate those that do not conceive 3 wk later. This allows specific matings, mating to superior sires and greatly minimizes the number of bulls needed. Artificial insemination coupled with three-breed rotation, terminal-sire crossbreeding systems offers the potential for maximum productivity. Feedlot Performance It is rather well documented that significant and meaningful differences in growth rate, feed efficiency and carcass composition exist among currently available genetic resources at the same age or weight (figure 1; Koch et al., 1976; 1979; 1982; Cundiff et al., 1981). However, the end point used to evaluate efficiency differences has a major effect on the rank of different breed groups for feed efficiency (figure 2; Cundiff et al., 1981). Evaluations at weight constant or gain constant bases probably are not very relevant for genotypes differing in growth rate, muscling and body fat. When cattle are fed to equal carcass composition, differences between breed groups in energy per unit of live weight gain are usually small, and the breed groups that deposit adipose tissue rapidly relative to muscle are generally slightly more efficient in energy required per unit of live weight gain. That is because of the large weight differences between genotypes at slaughter, which affect the proportion of feed used for maintenance. However, when efficiency is evaluated at constant marbling, but expressed as feedlot metabolizable energy consumed per unit of retail product, the more muscular, faster growing breed groups are more efficient because they have a higher percentage of retail product at a constant marbling end point. Time-on-feed affects marbling as well as total carcass fatness. When the desired output is closely trimmed retail product with acceptable palatability characteristics, long feeding periods on diets with high energy density are counterproductive to increasing production efficiency, especially for earlier maturing genotypes. Experiments with young castrate males of either small or large biological type placed on feed shortly after weaning suggest that increased energy density of the diet above 2.4 Meal metabolizable energy (ME)/kg dry matter will increase rate of gain, but at least 85% or more of the increased gain may be fat. When th rib soft tissue percentages of lipid, protein and water were used as estimators of composition, Smith et al. (1977) concluded that dietary energy densities above 2.7 Meal ME/kg dry matter resulted in mostly fat deposition. When specific gravity was used to predict carcass composition, Byers (1980) reported that daily empty body protein gain approached a maximum rate as empty body average daily gain reached.75 kg/d. Faster rates of gain result in no additional protein gain but rapidly accelerates rate of fat $. Devon Slmment81 Jersey Angus Hereford 1LIn~ousin I Charolals T T RETAIL PRODUCT AT 457 D, KG Figure 1. Distributions for breeds in retail product growth to 457 d (from Cundiff, 1983).

6 1636 DIKEMAN TDN/UNIT OF GAIN DIFFERENT INTERVALS OF EVALUATION L rr"ll II i l l C Ci C Ci L C L Ci MA G N-l-'l Io g]121 G BS,Si MAG BS Si BS MA Si [-! Br Sa P Ir'll--I $9 T II HA R I J I I I I I TDN/UNIT GAIN TIME CONSTANT I Br r"l--! SOP T II HA II R II Sa I J I I I I I I i i i TDN/IJNIT GAIN WEIGHT CONSTANT II'--! SO P C! Sa Br T! l HA R I J I! I i I TDN/UNIT GAIN MARBLING CONSTANT Figure 2. Rankings of different breed groups for feed efficiency. A = Angus, Br = Brahman, BS = Brown Swiss, C = Charolais, Ci = Chianina, G = Gelbvieh, H = Hereford, J = Jersey, L = Limousin, MA - Maine Anjou, P - Pinzgauer, R = Red Poll, Sa = Sahiwal, Si - Simmental, SD = South Devon, T = Tarentaise. deposition. Rampala and Byers (1978) also reported that rates of protein deposition approach limits of physiological potential at.7 to 1.0 kg/d. Gregory (1982) stated that in young castrate males that have high growth potential, the voluntary feed intake is greater than the ability to synthesize protein, even when dietary protein is not a limiting factor. With the current feeding, grading, processing and marketing system for cattle, the concept of feeding for muscle growth rather than maximum live weight gain is not yet applicable. The USDA Choice grade is stiu the "norm" for the industry, and cattle feeders, meat packers, retailers and restaurateurs primarily are oriented to the production and marketing of Choice grade beef. Byerly (1975) stated that grain provided to fattening cattle increased from approximately 6.5 million metric tons in 1950 to 35 million metric tons in High concentrate feeding of 110 to 160 d generally is required to develop enough marbling to attain 65 to 75% Choice carcasses, and as a result, excess body fat is deposited. Because muscle consists of 70 to 70% water, the above maintenance feed energy cost for muscle is little more than one-fourth that of fat, even though energy costs for tissue protein and fat are both about 54 kj/g (PuUar and Webster, 1977; Thorbek, 1977). Thus, reducing fat in slaughter cattle would improve feed efficiency greatly. The beef processing industry generally categorizes the five USDA yield grades into desirable (1, 2 and 3) and undesirable (4 and 5) categories, and usually has not priced carcasses of yield grades 1, 2 and 3 differently, even though significant curability differences exist among yield grades. Only recently have packers paid premiums for yield grade 2 amounting to about $4/100 kg carcass. Meat packers are more concerned with dressing percentage and percentage of Choice carcasses than they are of cutability differences, as long as the proportion of yield grade 4 and 5 carcasses is less than 5% of the cattle slaughtered. Consequently, cattle feeders utilize high energy diets to attain maximum gains, to attain 65 to 75% Choice

7 FUTURE DEMANDS ON CATTLE PRODUCTION SYSTEMS 1637 grade carcasses and to attain a high dressing percentage. Simulation analyses by Brokken et al. (1980) and Yorks et al. (1980) suggested that relatively long feeding periods on high energy diets may be the most economical system for producing beef. However, neither study considered a real value endpoint, such as trimmed retail product. Another obstacle to greater price incentives for yield grades 1 and 2 is that NAMP (1976) specifications still allow up to 1.9 cm fat cover on most subprimal cuts, and most of that fat still needs to be removed before reaching the consumer. If specifications allowed only 1.0 cm fat cover, for example, processors likely would discriminate more against yield grade 3, and pay more premium for grades 1 and 2. The industry will be forced eventually to market cattle with considerably less fat to improve efficiency and meet consumer demands for leaner beef that is competitively priced. The most likely practices to achieve that will be to shorten the finishing period on high energy diets and(or) deemphasize the importance of marbling in the USDA quality grading system. Only when the beef processing industry is highly oriented to pricing on yield of retail product rather than quality grade (marbling) and dressing percentage will cattle feeders consider finishing cattle on lower energy diets to limit fat deposition. Maximum rates of gain for shorter intervals should reduce nonfeed costs more than feeding lower energy diets for longer intervals. On the other hand, costs for cereal grain production could increase to the point that cereal grains may be used primarily to enhance the value of forage feed resources, and the use of grains to assure acceptable meat palatability could become much less feasible. Continued use of grains for finishing will be decided by economics (price of feed grains). Koch and Algeo (1983) stated that the importance of ruminants will increase rather than decrease in the future. These authors further stated that expansion in beef production from forages, by-products and crop residues could result in a major increase in protein production. However, this will require the development of new rumen-regulating drugs, new rumen microorganisms, prefeeding alterations of feedstuffs and other research breakthroughs. Reid and Klopfenstein (1983) stated that the trend in beef production will be toward less intensive feeding systems and more effective use of roughages by achieving near total utilization of the digestible energy in them. However, this is somewhat of a contradiction to the concept of "accelerated" production systems. These systems involve feeding high energy diets to fast growing, later maturing, muscular genotypes beginning shortly after weaning. These cattle are slaughtered by 13 to 15 mo of age, resulting in efficient gains and high cutability carcasses. Several studies have shown these systems to be profitable (Myers et al., 1979; Olsen, 1981). Even though accelerated production is considered an intensive system and contradicts the predicted trend of less intensive feeding discussed by Reid and Klopfenstein (1983), the proportion of cattle that are available for accelerated production may not be that high. It is relatively important that carcass weight not be reduced drastically as cattle are slaughtered with less body fat. Increased use of terminal-sire crossbreeding programs and the selection for increased size and leanness that is occurring in nearly all breeds should compensate for the weight reduction that results from slaughtering cattle with less body fat. Recently imported breeds, such as Simmental, Charolais, Limousin, Gelbvieh and Brown Swiss, have been used as terminal sire breeds in mating with Angus-Hereford reciprocal crossbred cows to reduce carcass fatness and increase muscling. Although USDA quality grades are generally lower for these crossbreds than for Angus- Hereford reciprocal crossbreds at similar ages, meat palatability is not different (table 1; Koch et al., 1976). Noncastrated Males Males are castrated primarily to improve ease of management and to improve carcass and meat traits. Yet, noncastrated males have about 15% faster growth rates than steers. Becuase of this, and the fact they are 25 to 30% leaner at the same age, noncastrated males are about 12% more efficient in feed conversion than castrated males (Oltjen, 1982). Noncastrated males also produce 20% more protein'dayq'unit -1 of digestible energy consumed than castrated males. However, when noncastrated males and castrated males are fed to equal body composition end points, the efficiency advantage of noncastrated males is minimized. This occurs because the castrated males reach equal body composition at lighter weights and, therefore,

8 1638 DIKEMAN TABLE 1. BREED GROUP MEANS FOR FACTORS IDENTIFIED WITH MEAT QUALITY AT 458 DAYS OF AGE a Breed crosses Warner- Bratzler Percentage shear, Marbling b choice kg Flavor c Juiciness c Tenderness c Chianina- (Ci) Limousin- (L) Brahman- (Br) Gelbvieh- (G) Sahiwal- (Sa) Simmental- (S) Maine-Anjou- (MA) ~ Tarentaise- (T) Charolais- (C) Brown Swiss- (BS) i Pinzgauer- (P) South Devon- (SD) Hereford-Angus-X (HA) Red Poll- (R) Jersey- (J) afrom Cundiff (1983). bmarbling: 5 = traces; 8 = slight; 11 = small; 14 = modest 17 = moderate. CTrained sensory panel scores: 9 = extremely tender, juicy or flavorful,... 1 = extremely tough, dry or bland. have lower maintenance requirements. Klosterman and Parker (1976) concluded that differences among sexes in rate of gain, feed efficiency, rate of maturing, carcass weight and carcass composition are similar to differences that exist among different biological types of cattle in regard to size. Nevertheless, it has been estimated that 19% more retail product could be produced without increasing the reproducing herd or feed resources, if all males were not castrated, and assuming that 50% of U.S. beef production is from young castrated males (Gregory, 1982). That estimate may also assume that noncastrated males would be managed like castrated males, which is not valid. Leaving males intact reduces the flexibility in management. They are not practical in deferred feeding systems because of behavior problems and the meat sensory problems that occur after about 16 to 18 mo of age. Noncastrated males are much more likely to have dark, firm and dry lean (high ph), lower USDA quality grades and beef that is generally less tender and juicy than steer beef (Field, 1971; Seideman et al., 1982; Smith, 1982). Arthaud et al. (1969, 1977) reported more variation in tenderness of noncastrated males than in castrated males. The relatively high incidence of dark cutters is minimized when stress before slaughter is prevented by avoiding mixing of noncastrated males from different pens (Tennessen and Price, 1980; Price and Tennessen, 1981). Even so, retail shelf-life of beef from noncastrated males is less than that from castrated males. The USDA grading system further discriminates against noncastrated males by identifying them as "Bullocks" when muscle quality and secondary sex characteristics fit certain descriptions. The connotation of the term "Bullock" is generally undesirable in the industry and to the consumer. Therefore, there is considerable feedlot, beef processor, retailer and consumer resistance (indirectly) to beef from noncastrated males under present production, grading and processing systems. Finishing noncastrated males to meet consumer demands for beef likely wiu be limited unless new management, processing and marketing systems are utilized. Research on implanting noncastrated males early in life with exogenous estrogen-like compounds (zeranol) significantly altered masculinity development in studies by Greathouse et al. (1983) and Unruh et al. (1983). Weight per day of ag e was increased with implanting in the study by Great-

9 FUTURE DEMANDS ON CATTLE PRODUCTION SYSTEMS 1639 house et al. (1983), but was decreased slightly in the study by Gray et al. (1983). Implanted bulls in both studies generally had more fat covering than nonimplanted bulls, although quality grades were not different. Tenderness was improved by implanting from birth to slaughter in studies by Gray et al. (1983) and Greathouse et al. (1983). These results suggest potential for "modifying" noncastrated males with exogenous compounds by affecting masculinity and making beef more tender without significantly sacrificing growth and feed efficiency advantages. However, more research is needed. The cow-calf producer should know by calving time whether he has a market for noncastrated males either as feeder calves or as fed bulls for slaughter. Industry discrimination of noncastrated males is due largely to mismanagement and by producers not seeking a market until there is no acceptable alternative to finishing noncastrated males for slaughter. Factors Related to Beef Quality The present beef processing and merchandising system places too much emphasis on "feeding quality into beef" rather than relying on postmortem technology to enhance or add to the quality. The current grading system may be partly responsible for that, yet man has believed since Biblical times that fat animals produce more tender, succulent meat than animals that have little fat. Presently, a certain level of fatness is considered essential to achieve acceptable meat sensory characteristics. Although marbling is positively and significantly related to palatability, it accounts for only about 10% of the variation in beef tenderness, and slightly more of the variation in juiciness and flavor. However, when beef is cooked to high internal temperatures (mediumwell or well done), marbling becomes somewhat more important in predicting palatability (Parrish, 1981). When different breed groups were fed to a constant age end point, such that Angus Hereford reciprocal crosses graded 70 to 75% Choice, no significant differences in taste panel palatability or Warner-Bratzler shear force of the longissimus muscle were observed, except that Sahiwal and Brahman crosses produced a significant percentage of carcasses that had low tenderness scores (table 1; Cundiff, 1983). Other studies also have shown that Zebu crossbred cattle are less tender than Bos taurus crossbred cattle. Koch et al. (1982) reported significantly lower USDA quality grades for Brahman and Sahiwal crossbreds, and yet they had almost no advantage in yield grade. Therefore, carcasses and meat from Zebu crossbred cattle generally are less desirable than from most Bos taurus crossbreds. Carcass fat cover indicates many of the same things that marbling indicates because marbling and fat thickness are moderately highly correlated. The amount, and perhaps the kind, of external fat cover should be a good measure of the kind of diet cattle have been fed and the length of time they have been fed. Fat cover further determines the rate of carcass chilling, which can affect tenderness and flavor. Marsh and Lochner (1981) stated that the role of fat in promoting tenderness (and probably other attributes as well) is to prolong early postmortem high temperature in muscle. Several studies confirming that fat thickness relates to palatability, and that cattle have been fed a high quality diet have been conducted by McBee and Wiles (1967), Merkel and Pearson (1975), Bowling et al. (1977), Meyer et al. (1977), Jennings et ai. (1978), Young and Kauffman (1978), Dikeman et al. (1979), Smith (1980) and Dikeman and Kemp (1981). An additional advantage of fat thickness or a fat score is that it could be used for grading carcasses prerigor, before hot boning. For young cattle, whether marbling and(or) fat cover is used as the primary determinant of quality grade, the fact remains that cattle feeders are still required to "feed quality into beef." With that concept, it has been proposed that a "time-on-feed certification system" be substituted for the current USDA grading system. Numerous research studies (Wanderstock and Miller, 1948; Epley et al., 1968; Zinn et al., 1970; Bowling et al., 1978; Dinius and Cross, 1978; Harrison et al., 1978; Leander et al., 1978; Skelly et al., 1978; Schupp et al., 1979; Bulgerin et at., 1980; Burson et al., 1980; Davis et al., 1980; Dyer et al., 1980; Tatum et al., 1980; Dikeman et al., 1981) have shown that feeding a moderate to high-energy diet for a minimum of 90 to 100 d results in palatability equivalent to that of the Choice grade. Feeding more than 100 d results in only slight improvements in palatability of cattle similar in type. Research on meat palatability and its relationship with carcass fatness indicates that

10 1640 DIKEMAN cattle can be marketed at an earlier point on the growth curve when they have considerably less body fat without any significant effect on meat palatability. Postmortem technologies can more than compensate for the slight decrease in palatability that might occur from slaughtering cattle that have 15% fat trim (Good grade) compared with 19.5% fat trim (lower one-half of the Choice grade; M. E. Dikeman, unpublished data on 2,537 carcasses). Numerous beef processing plants already are using electrical stimulation (ES) to improve visual quality of beef, which brings about a higher proportion of Choice carcasses (Savell and Smith, 1981). Results of research studies conducted on ES effects on beef palatability range from no improvement in tenderness and flavor to very significant improvements. These variable results may stem from the variation in the manner in which ES is applied. Also, some muscles may not be affected by ES. Savell (1979) stated that ES improves tenderness an average of 21% and flavor, 10%. Even though some studies have not shown improvements in palatability (Kasmer et al., 1980), ES is a practical technology that generally has beneficial effects. When ES is used in combination with prerigor boning (hot boning), color is significantly improved when cuts are displayed in vacuum packages (Claus et al., 1981). Electrical stimulation makes hot boning feasible by accelerating ph decline to prevent cold toughening [Davey et al., 1976; Gilbert and Davey, 1976; Axe (Bowles) et al., 1983]. On the other hand, extremely rapid rates of ph decline may result in a pale, soft and(or) exudative condition. In some cases color may be so pale that USDA grading standards will not allow carcasses to be graded. It would seem that the optimum combination of ES conditions has not yet been determined for consistently improving tenderness and preventing detrimental meat color effects. Delayed chilling, that is, holding carcasses at 16 C or higher for 3 to 24 h postmortem before chilling has been shown to improve tenderness 7 to 47% (Finney, 1981). Unfortunately, all muscles do not respond to the same extent and microbial proliferation is a potential problem with this technique. More importantly, industry application would require additional holding facilities and would increase inventory of carcasses. However, as much change in palatability probably could be made by 6 to 8 h of delayed chilling as by the last 30 d on a 140-d high concentrate feeding regimen. Marsh (1983) has shown that holding carcasses 3 h at 37 C before chilling accelerates postmortem enzymatic activity, resulting in improved tenderness, even for muscles with ph still above 6. Aging primal or subprimal cuts in vacuum packages is a growing practice because it allows aging to occur without microbial growth and moisture loss (Finney, 1981). The industry should utilize this technique to a greater extent, especially for muscles merchandised as steaks. Mechanical blade tenderization is an effective method of tenderizing beef. Tenderness can be improved 19 to 32% by affecting both myofibrillar and connective tissues (Finney, 1981). Furthermore, this technique is easy to apply. It is more beneficial to muscles high in connective tissue and, therefore, has less application to muscles that are inherently tender. However, cooking losses may be increased as well as rate of cooking. As the proportion of the carcass that is ground or made into restructured products increases, the need for mechanical blade tenderization may diminish. Prerigor boning (hot boning) has attracted considerable attention because of the processing efficiencies that are attributed to this technology. Cooler space requirements and refrigeration energy input can be reduced an estimated 52 and 42%, respectively (Erickson et al., 1980). In addition, labor requirements are about 25% less than for postrigor boning. There are potential tenderness problems that can be associated with prerigor boning unless proper precautions are taken. Kasmer (1977) reported that equal or superior palatability and yield can be achieved with prerigor boning compared with cold boning. Electrical stimulation and delayed chilling are two of the most effective methods for assuring equal palatability of hot-boned beef to that of cold-boned beef. One of the major deterrents to industry application of this technology is that USDA grade standards are not applicable to hot carcasses. Therefore, hot carcasses cannot be graded and, unless a method is developed to grade hot carcasses, industry adaption of this efficiency-improving technology will be limited for young, grain-finished cattle. However, it offers significant potential for carcasses destined for ground beef, restructured products or sausage production. Even though obstacles now exist to widespread industry usage of these various postmortem technologies, it has been demonstrated

11 FUTURE DEMANDS ON CATTLE PRODUCTION SYSTEMS 1641 that they can enhance palatability, particularly tenderness. Some of them can increase palatability more than the last 30 to 50 d of a 140 d finishing period. Crouse and Smith (1978) demonstrated that, for A maturity cattle, a dramatic change in marbling was required to make a one-score increase in sensory panel tenderness. This means that the last 30 to 50 d of a conventional feeding period result in almost no change in tenderness. Garcia-de-Siles et al. (1977) concluded from a large study that the emphasis that marbling receives in carcass grading is not justified in predicting meat palatability from relatively young cattle that have received a high energy diet. Therefore, it is expected that technology will assume a greater role in the future of assuring or enhancing beef quality. Literature Cited AHA Diet and Coronary Heart Disease. Amer. Heart Assoc. Committee Rep. Circulation 58(4): 762A. Arthaud, V. H., C. H. Adams, D. R. 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