Department of Animal and Food Sciences, Texas Tech University, Lubbock, TX 79409, USA.
Beckett Consulting Services, Fort Collins, CO 80524, USA.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad239.
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 following embryo transfer to Holstein dams (H ET; n = 15) and Jersey dams (J ET; n = 16) The finishing trial began when cattle weighed 301 ± 32.0 kg and concluded after 195 ± 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 (A × B, H ET, and J ET) and A × H were similar in final shrunk body weight, dry matter intake, and carcass weight (P > 0.05 for each variable). Compared with A × J cattle, J ET was 42 d younger at slaughter with 42 kg 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.
改良的繁殖管理使得奶牛妊娠能够优化以用于牛肉生产。本项由父本控制的研究目的是检验在牛犊牧场中饲养的纯种肉牛犊的肥育性能，并比较其育肥生长性能、胴体特征和与肉牛×奶牛杂交牛和传统肉牛母牛/犊牛系统中饲养的纯种肉牛的机械响应。测试的处理组包括在牧场饲养的纯种肉牛公牛和母牛（A×B；n=14）、通过胚胎移植到荷斯坦奶牛（H ET；n=15）和泽西奶牛（J ET；n=16）的母奶牛所产的纯种肉牛公牛和母牛。育肥试验于牛体重 301±32.0 kg 时开始，195±1.4 d 后结束。从第 28 天开始，每头牛的个体采食量都有记录，直到运往屠宰场。每 28 d 对所有牛进行称重；每隔 56 d 从部分公牛采集血清。在最终的收缩体重、干物质摄入量和胴体重量方面，纯种肉牛遗传（A×B、H ET 和 J ET）和 A×H 的牛相似（每个变量的 P 值均大于 0.05）。与 A×J 牛相比，J ET 的屠宰年龄小 42 d，胴体重量多 42 kg（两个变量的 P 值均小于 0.05）。所有处理之间的背最长肌面积无差异（P=0.40）。脂肪厚度以纯种肉牛牛最大，A×J 牛最小，A×H 牛居中（P<0.05）。当根据调整后的最终体重百分比进行调整时，与肉牛×奶牛杂交牛相比，纯种肉牛的饲料效率更高（P=0.04）。观察到处理×天的循环胰岛素样生长因子 I（IGF-I；P<0.01）的相互作用；在被植入后 112 d，肉牛×奶牛杂交牛的循环 IGF-I 浓度大于纯种肉牛遗传牛（P<0.05）。泽西奶牛所产的纯种肉牛犊在牛犊牧场的肥育和胴体性能方面比 A×J 杂交牛更高效。传统饲养或在牛犊牧场饲养的纯种肉牛犊在肥育场中的表现相似。
