Beef Carcass Research Center - Department of Agricultural Sciences, West Texas A&M University, Canyon, TX.
Merck Animal Health, Summit, NJ.
J Anim Sci. 2018 May 4;96(5):1688-1703. doi: 10.1093/jas/sky105.
A trial was conducted to examine live growth efficiency, harvest yields, and carcass grading performance of steers fed at maintenance (M) or at ad libitum (A) level of intake during zilpaterol hydrochloride (Z) supplementation. Single-sired, beef steers (n = 56; start of trial BW 590 ± 36 kg) blocked (n = 2) by weight and terminal implant were sorted into pairs (n = 14 per block) by weight. Pairs of steers were initially assigned to 0, 28, or 56 d of feeding. Within 28 or 56 d, pairs were assigned to M or A intake. Steers within a pair assigned to 56 d of feeding were randomly assigned to either 20 d of Z supplementation (90 mg/d per steer) with a 4 d withdrawal period prior to slaughter or to no ZH supplementation (C). Steers were housed and fed in individual pens. Weights of all non-carcass and carcass components were recorded at slaughter; carcasses were graded 24-h postmortem. Data were analyzed via a mixed model; the fixed effect was treatment combination with random effects of block and pair. Live growth data used harvest day as the repeated measure and animal as the subject. Single df contrasts were constructed for day 0 vs. day 28, day 0 vs. day 56, day 28 vs. day 56, M vs. A, and C vs. Z. Treatment impacted (P ≤ 0.05) live ADG; contrasts indicated A (1.33) was greater than M (0.14 kg), and Z (1.12) was greater than C (0.82 kg). Similarly, carcass ADG differences (P < 0.01) indicated A (1.04) was greater than M (0.36 kg), and Z (1.35) was greater than C (0.71 kg). Intake level altered BW and empty body weight (EBW); M cattle had reduced BW and EBW (P < 0.01, 585 and 540 kg) than A cattle (647 and 597 kg). Cattle fed at M had less carcass and internal cavity mass (P < 0.01, 359 and 79.4 kg) than A cattle (394 and 93.5 kg). Liver mass was reduced by M feeding (P < 0.01; M-5.03, A-6.69 kg) and Z treatment (P < 0.01; Z-5.64, C-6.06 kg). Moreover, mass of total splanchnic tissue was less (P < 0.01) for M cattle than A cattle (59.8 vs. 72.5 kg). Dressed carcass yield was greater (P < 0.01) for Z than C cattle (63.5 vs. 61.6%). Cattle fed at M had less 12th rib s.c. fat, lower numerical U.S. yield grades (P < 0.01; M-1.71 cm and 3.3, A-2.46 cm and 4.3) and lower numerical Canadian yield grades (P < 0.01; 51.9 vs. 53.9% for M and A, respectively) than A cattle. Results indicate that energy intake level and Z supplementation influence live and carcass growth, carcass transfer, kill yields, and carcass characteristics across time.
一项试验旨在研究盐酸齐帕特罗（Z）补充剂喂养下维持（M）或自由采食（A）水平时的育肥牛的活体生长效率、收获产量和胴体分级性能。单胎、肉牛（试验开始体重 590±36kg）按体重分为 2 组（每组 2 个重复），并进行终端植入。根据体重将牛分为两组（每组 14 对），每组接受 0、28 或 56 天的喂养。在 28 或 56 天内，每组被分配到 M 或 A 采食量。接受 56 天喂养的牛组被随机分配到以下两组中的一组：20 天 Z 补充（每头牛每天 90mg），然后停药 4 天屠宰，或不接受 ZH 补充（C）。牛被单独饲养在单个围栏中。所有非胴体和胴体成分的重量均在屠宰时记录；胴体在死后 24 小时进行分级。数据通过混合模型进行分析；固定效应为处理组合，随机效应为块和对。活体生长数据使用收获日作为重复测量，动物作为主体。构建了单自由度对比，用于比较 0 天与 28 天、0 天与 56 天、28 天与 56 天、M 与 A 以及 C 与 Z。处理影响（P≤0.05）活体 ADG；对比表明 A（1.33kg/d）大于 M（0.14kg/d），Z（1.12kg/d）大于 C（0.82kg/d）。同样，胴体 ADG 差异（P＜0.01）表明 A（1.04kg/d）大于 M（0.36kg/d），Z（1.35kg/d）大于 C（0.71kg/d）。采食量水平改变了 BW 和空腹体重（EBW）；M 牛的 BW 和 EBW 低于 A 牛（P＜0.01，585 和 540kg）（647 和 597kg）。M 组牛的胴体和内脏腔质量（P＜0.01，359 和 79.4kg）低于 A 组牛（394 和 93.5kg）。M 饲养减少了肝脏质量（P＜0.01；M-5.03，A-6.69kg）和 Z 处理（P＜0.01；Z-5.64，C-6.06kg）。此外，M 饲养减少了总肠系膜组织的质量（P＜0.01；M-59.8kg，A-72.5kg）。Z 组牛的去骨胴体产量大于 C 组牛（P＜0.01；63.5% vs. 61.6%）。M 组牛的第 12 肋骨皮下脂肪较少，美国产肉等级较低（P＜0.01；M-1.71cm 和 3.3，A-2.46cm 和 4.3），加拿大产肉等级较低（P＜0.01；M 和 A 组分别为 51.9%和 53.9%）。结果表明，能量摄入水平和 Z 补充剂影响活体和胴体生长、胴体转移、屠宰产量和胴体特性随时间的变化。
