Beef embryos in dairy cows: Feedlot performance, mechanistic responses, and carcass characteristics of straightbred Holstein calves and Angus-sired calves from Holstein, Jersey, or crossbred beef dams.

Abstract

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 beef × 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 (A×B; n = 14), straightbred beef steers and heifers born to Holstein (H ET; n = 15) and Jersey dams (J ET; n = 16), Angus × Holstein crossbreds (A×H; n = 15), and Angus × Jersey crossbreds (A×J; n = 16). The finishing trial began when cattle weighed 301 ± 32.0kg and concluded after 195 ± 1.4 d. Individual intake was recorded from d 28 until shipment for slaughter. All cattle were weighed every 28 days; serum was collected from a subset of steers every 56 days. Cattle of straightbred beef genetics (A×B, H ET and J ET) and A×H were similar in final shrunk BW, dry matter intake (DMI), and carcass weight (P > 0.05 for each variable). Compared with A×J cattle, J ET were 42 days younger at slaughter with 42kg more carcass weight (P < 0.05 for both variables). No difference was observed in longissimus muscle area between all treatments (P = 0.40). Fat thickness was greatest for straightbred beef cattle, least for A×J cattle, and intermediate for A×H cattle (P < 0.05). When adjusted for percentage of adjusted final body weight, feed efficiency was greater for straightbred beef cattle compared with beef × dairy crossbred cattle (P = 0.04). A treatment × day interaction was observed for circulating insulin-like growth factor I (IGF-I; P < 0.01); 112 d after being implanted, beef × dairy crossbred cattle had greater circulating IGF-I concentration than cattle of straightbred beef genetics (P < 0.05). Straightbred beef calves born to Jersey cows had more efficient feedlot and carcass performance than A×J crossbreds. Calves of straightbred beef genetics raised traditionally or in a calf ranch performed similarly in the feedlot.