RESUMO
Improved reproductive management has allowed dairy cow pregnancies to be optimized for beef production. The objective of this sire-controlled study was to test the feedlot performance of straightbred beef calves raised on a calf ranch and to compare finishing growth performance, carcass characteristics, and mechanistic responses relative to beefâ ×â dairy crossbreds and straightbred beef cattle raised in a traditional beef cow/calf system. Tested treatment groups included straightbred beef steers and heifers reared on range (Aâ ×â B; nâ =â 14), straightbred beef steers and heifers born following embryo transfer to Holstein dams (H ET; nâ =â 15) and Jersey dams (J ET; nâ =â 16) The finishing trial began when cattle weighed 301â ±â 32.0 kg and concluded after 195â ±â 1.4 d. Individual intake was recorded from day 28 until shipment for slaughter. All cattle were weighed every 28 d; serum was collected from a subset of steers every 56 d. Cattle of straightbred beef genetics (Aâ ×â B, H ET, and J ET) and Aâ ×â H were similar in final shrunk body weight, dry matter intake, and carcass weight (Pâ >â 0.05 for each variable). Compared with Aâ ×â J cattle, J ET was 42 d younger at slaughter with 42 kg more carcass weight (Pâ <â 0.05 for both variables). No difference was observed in longissimus muscle area between all treatments (Pâ =â 0.40). Fat thickness was greatest for straightbred beef cattle, least for Aâ ×â J cattle, and intermediate for Aâ ×â H cattle (Pâ <â 0.05). When adjusted for percentage of adjusted final body weight, feed efficiency was greater for straightbred beef cattle compared with beefâ ×â dairy crossbred cattle (Pâ =â 0.04). A treatmentâ ×â day interaction was observed for circulating insulin-like growth factor I (IGF-I; Pâ <â 0.01); 112 d after being implanted, beefâ ×â dairy crossbred cattle had greater circulating IGF-I concentration than cattle of straightbred beef genetics (Pâ <â 0.05). Straightbred beef calves born to Jersey cows had more efficient feedlot and carcass performance than Aâ ×â J crossbreds. Calves of straightbred beef genetics raised traditionally or in a calf ranch performed similarly in the feedlot.
Improved reproductive management has allowed dairy cow pregnancies to be optimized for beef production. The objectives of this study were to use an embryo transfer model 1) to investigate the effect of the dairy management system on beef genetics and 2) to directly compare the merit of Holstein and Jersey genetics for feedlot and carcass performance with modern beef genetics. Feedlot and carcass performance of straightbred beef cattle were similar regardless if the calf was raised in the traditional beef cow/calf system or if the calf was raised at a calf ranch. Based on greater daily live gain and carcass weight, Holstein maternal genetics had greater terminal merit than Jersey maternal genetics. Regardless of dam breed, dairy genetics increased carcass leanness. Minimal differences were detected between adjusted feed efficiency of beef and beefâ ×â dairy cattle, but underestimation of mature size of beefâ ×â dairy could have overestimated efficiency. Genetic differences were more impactful than differences between the conventional beef and dairy calfhood management systems on feedlot and carcass performance.
Assuntos
Composição Corporal , Fator de Crescimento Insulin-Like I , Gravidez , Animais , Bovinos/genética , Feminino , Composição Corporal/genética , Reprodução , Parto , Peso CorporalRESUMO
The use of beef bulls on dairy cattle has increased in the last 6 years. In fact, beef semen sales have more than doubled. Dairyman needs to capture real value for the beef on dairy cross calf, selection of beef sires that produce offspring that complement dairy cattle are needed, not simply the cheapest black bull in the tank. Those beef sires should be selected on calving ease, ribeye area, marbling, feed efficiency, fertility, polled, and an industry preference for black hided. Even more important, the use of beef on dairy has allowed dairy producers to manage replacement animal inventories.