A theory of beef production

Groups of maiden heifers (105 dairy and 119 beef) were treated twice with an 11-day-interval between injections of Cloprostenol (0.5 mg/i.m.), and were then inseminated at 72 h and 96 h after the second injection. The pregnancy rate (PR) was 39% in both types of heifers. Significant PR differences between groups of heifers were largely due to differences in the proportion of non-cycling (anoestrus) animals within each group. Excluding these animals from the analyses increased PR's to the set-time inseminations by over 11%.

An alternative treatment regime was used in a second series of trials. Entire bulls fitted with chin-ball mating harnesses were run with groups of heifers. Those heifers served in the first 11-day-period were subsequently injected with 0.5 mg of Cloprostenol 6 days later and inseminated 72 h and 96 h after treatment. The second sub-group of heifers served in the second 11-day-period received the same injection-insemination sequence. Unmated heifers were examined at the same time as the second sub-group was injected. The PR among the 90 treated dairy heifers (from a total of 102 animals) was 69%, and 58% in 163 treated beef heifers. Almost all of the heifers not served by bulls in the pretreatment period were subsequently found to be anoestrus, pregnant to a previous (unrecorded) mating, or abnormal (freemartin).

The use of oestrus synchronisation in maiden heifers can facilitate the use of AB with associated advantages through genetic improvement. The additional advantages in aspects of herd management, particularly in the reduction in the time-span of conventional AB programmes, may be its greatest use. In either case, the pretreatment identification, and the exclusion of heifers which cannot be successfully synchronised, will be important in obtaining satisfactory results.     

Antimicrobial usage and resistance in beef production

Antimicrobials are critical to contemporary high-intensity beef production. Many different antimicrobials are approved for beef cattle, and are used judiciously for animal welfare, and controversially, to promote growth and feed efficiency. Antimicrobial administration provides a powerful selective pressure that acts on the microbial community, selecting for resistance gene determinants and antimicrobial-resistant bacteria resident in the bovine flora. The bovine microbiota includes many harmless bacteria, but also opportunistic pathogens that may acquire and propagate resistance genes within the microbial community via horizontal gene transfer. Antimicrobial-resistant bovine pathogens can also complicate the prevention and treatment of infectious diseases in beef feedlots,threatening the efficiency of the beef production system. Likewise, the transmission of antimicrobial resistance genes to bovine-associated human pathogens is a potential public health concern. This review outlines current antimicrobial use practices pertaining to beef production, and explores the frequency of antimicrobial resistance in major bovine pathogens. The effect of antimicrobials on the composition of the bovine microbiota is examined, as are the effects on the beef production resistome. Antimicrobial resistance is further explored within the context of the wider beef production continuum, with emphasis on antimicrobial resistance genes in the food chain, and risk to the human population.     

肉牛规模化生产综合配套技术

1牛舍建造 选择地势高燥、平坦、阳光充足、通风良好、坐北朝南的地方,可修筑单列、双列封闭舍,也可建造敞圈,但冬季应扣塑料暖棚,每头牛应保证4～5m2面积.     

Crossbreeding cattle in beef production programmes in Kenya

Data collected on a privately owned ranch located in the Machakos District of Kenya at approximately 2 degrees latitude south of the equator at an elevation varying from 1,675 to 2,000 m were analysed on five breed groups of cows: (1) purebred Boran, (2) 1/2 Charolais-1/2 Boran (1/2 C-1/2 B), (3) 3/4 Boran-1/4 Charolais (3/4 B-1/4 C), (4) 1/2 Ayrshire-1/2 Boran (1/2 A-1/2 B) and (5) 1/2 Santa Gertrudis-1/2 Boran (1/2 SG-1/2 B). The maternal traits evaluated included age at first calving, calving interval, calf weight at weaning and cow productivity index (calf weight weaned annually per cow calving). Mean cow productivity index for all cows was 192 kg; for purebred Boran, 174 kg; for 1/2 C-1/2 B, 200 kg; for 3/4 B-1/4 C, 191 kg; for 1/2 A-1/2 B, 210 kg; and for 1/2 SG-1/2 B, 185 kg. Cow breed groups 1/2 C-1/2 B, 3/4 B-1/4 C, 1/2 A-1/2 B and 1/2 SG-1/2 B exceeded (P less than 0.01) purebred Boran by 14.9, 9.8, 20.7 and 6.3%, respectively, in cow productivity index.     

Embryo-transfer twinning and performance efficiency in beef production

Effects of twinning on efficiency of beef production were estimated from results of bilateral transfer of two Angus x Hereford (AxH) embryos into each of 241 heifers and 84 cows (H, A, HxA or Holstein x H) over 4 yr. Calves were weaned at 180 d and fed either 220 d in a feedlot (1977) or 170 d on forage and 140 d in a feedlot (1978 to 1980). Effects of parity, twinning and sex of calf were estimated as covariates within year-breed of dam. Pregnancy at 45 to 60 d of gestation was 68% in heifers (H) and 74% in cows (C), with 40% single (S) and 60% twin (T) births. Dystocia was 28% in H vs 10% in C (P less than .05), and tended to be less (P greater than .05) for T than S in H. More placentas were retained (P less than .05) for T than for S in both H (35 vs 12%) and C (24 vs 4%). Twin gestations averaged 3 d shorter and subsequent calving intervals 13 d longer (P less than .05), but total calf mortality was slightly higher (P greater than .05). Abortions were 4% in H only. Twinning females lost maternal weight during late gestation (P less than .05) when crowding limited voluntary feed intake, while fetal requirements were 60% higher (P less than .01). Twins increased milk output 25% (P less than .05), but 11% higher feed intake maintained cow weight during lactation. Twinning reduced birth weight 13% and weaning weight 17% (P less than .05), but 400-d feedlot weight only 9% because of compensating feedlot gain. Twins gained 18% faster than S during postweaning 170-d forage feeding, but 5% slower in feedlot to 8% lighter 490-d weight (P less than .05). Assuming 40% higher veterinary and labor costs for twins, estimated integrated herd costs per unit of age-constant output value would be lower for T than for S production by about 24% for marketing either at weaning or at 400 d.     

Antimicrobial resistance in beef and dairy cattle production

Observational studies of cattle production systems usually find that cattle from conventional dairies harbor a higher prevalence of antimicrobial resistant (AMR) enteric bacteria compared to organic dairies or beef-cow operations; given that dairies usually use more antimicrobials, this result is not unexpected. Experimental studies have usually verified that application of antimicrobials leads to at least a transient expansion of AMR bacterial populations in treated cattle. Nevertheless, on dairy farms the majority of antibiotics are used to treat mastitis and yet AMR remains relatively low in mastitis pathogens. Other studies have shown no correlation between antimicrobial use and prevalence of AMR bacteria including documented cases where the prevalence of AMR bacteria is non-responsive to antimicrobial applications or remains relatively high in the absence of antimicrobial use or any other obvious selective pressures. Thus, there are multi-factorial events and pressures that influence AMR bacterial populations in cattle production systems. We introduce a heuristic model that illustrates how repeated antimicrobial selection pressure can increase the probability of genetic linkage between AMR genes and niche- or growth-specific fitness traits. This linkage allows persistence of AMR bacteria at the herd level because subpopulations of AMR bacteria are able to reside long-term within the host animals even in the absence of antimicrobial selection pressure. This model highlights the need for multiple approaches to manage herd health so that the total amount of antimicrobials is limited in a manner that meets animal welfare and public health needs while reducing costs for producers and consumers over the long-term.     

Record systems for beef stocker production enterprises.

The accelerated growth of individual animal identification systems is likely to generate significant amounts of data that need to be synchronized, filtered, analyzed, managed, and acted on in real time by data-mining software and animal health professionals who possess a dual understanding of beef systems production and technology associated with management information and record-keeping systems. Ultimately, the resulting information can be used seamlessly throughout a vertically coordinated production system to conduct management and animal health compliance audits, initiate timely animal and product recall measures, and reveal complex biologic and economic relations.     

Some overseas developments in sheep and beef production

Extract

Comment will be made on the sheep and cattle production scene as seen during a visit to the U.S.A. and Britain last year. Naturally this will be a personal interpretation of what a practising veterinarian from New Zealand was able to assimilate during visits to research organizations, commercial properties, and universities and by listening and talking to a variety of people interested in animal production. The problems associated with animal production are much the same the world over — efficiency of production, seeking the breeds suited to the environment, nutrition, diseases, reproductive ability and orderly marketing of the product. While the problems are the same the emphasis varies and the relative importance of any one will be different in different countries.     

Intensive fattening of beef cattle by stall feeding on the Lilongwe plain,Malawi

Beef fattening experiments were undertaken on the Lilonge Plain with Malawi zebu (Mz) and Friesian X Malawi zebu (F X Mz) steers. Animals were fattened under various dietary regimes based on either green forage crops or crop residues supplemented with concentrate rations of local origin. Mz steers consumed less feed and liveweight gain was approximately 75 per cent that of the F X Mz. Measurement of the efficiency parameters of feed conversion, gain and carcass yield per unit of liveweight revealed no significant differences between the two breed types. Slaughter observations indicated better fat distribution in the F X Mz and a significantly higher proportion of hindquarter. The significance of the results is discussed.     

Simulated efficiency of range beef production. I. Growth and milk production

A revised version of the Texas A&M University Beef Cattle Production Model was used to simulate the effects of growth, milk production and management system on biological and economic efficiency of beef production in a northern plains, range environment. Animals varying in genetic potential for birth weight (BWA), yearling weight (YW), mature weight (WMA) and milk production (PMA) were simulated under both a weanling system of management (weaned calves custom-fed in the feedlot) and a yearling system (calves wintered on the ranch, then custom-fed after their second summer). The yearling system of management was biologically less efficient, but economically more efficient than the weanling system due primarily to heavier slaughter weights of fed animals. The advantage of the yearling system was most apparent for smaller genotypes. Herd efficiency improved with decreased BWA and increased YW, but changed little when WMA was varied while other growth traits were held constant. Increased PMA was favored for production of live weight at weaning and for production of slaughter product when feedlot costs were high. Increased PMA was not favored when feed costs for the cow herd were high. Economic weights generated from the simulation indicated the importance of selection for rapid early growth followed by selection for lighter birth weight. While larger genotypes were generally favored in this study, optimal cow size depended on economic conditions. Larger types were more biologically efficient and more economically efficient using standard costs, but medium- and small-size cattle were more efficient when feedlot costs were high. Small cattle were least efficient when feed costs for the cow herd were high.     

Evaluation of intensive vs extensive systems of beef production and the effect of level of beef cow milk production on postweaning performance

Charolais-sired calves from three groups of beef cows, similar in growth potential and mature size but different in genetic potential for milk production (5.6, 7.7, 9.0 kg/d; low, medium, and high, respectively), were allotted to two beef production systems each year for 3 yr. At weaning, calves in an intensive (Int) system went directly into the feedlot for finishing (236 d); calves in an extensive (Ext) system were wintered on corn residues (195 d), grazed pasture (115 d) and then were finished (122 d). Postweaning effects of increased weaning weight due to increased level of milk were small and not affected by growing-finishing system. Only the steer calves from the low milk-producing cows showed evidence (P less than .01) of compensatory growth postweaning in response to reduced levels of milk during the suckling phase. Cattle from the Ext system were heavier (P less than .01) before (388 vs 233 kg) and after (595 vs 531 kg) the finishing phase than Int system cattle. During finishing, cattle from the Ext system made more rapid gains (1.70 vs 1.36 kg/d) and consumed more feed (12.4 vs 8.5 kg/d, 2.52 vs 2.19% of average BW) but were less efficient (.137 vs .160, gain/feed) than cattle from the Int system (P less than .05). Extensive systems of beef production produced more total kilograms of beef per animal but they were 196 d older at slaughter.     

我国肉牛业生产现状及对策

介绍了我国肉牛业的现状, 提出了保证我国肉牛业发展的５ 个环节, 即品种资源, 饲养管理, 屠宰工艺, 建立分级制度和烹调加工。