Department of Animal and Food Sciences, Texas Tech University, Lubbock 79409, USA.
J Anim Sci. 2012 Sep;90(9):3301-11. doi: 10.2527/jas.2011-4375. Epub 2012 Aug 7.
British × Continental heifers (n = 3,382; initial BW = 307 kg) were serially slaughtered to determine if increasing days on the finishing diet (DOF) mitigates negative consequences of zilpaterol HCl (ZH) on quality grade and tenderness of beef. A 2 × 3 factorial arrangement of treatments in a completely randomized block design (36 pens; 6 pens/treatment) was used. Zilpaterol HCl (8.33 mg/kg DM) was fed 0 and 20 to 22 d before slaughter plus a 3 to 5 d withdrawal to heifers spending 127, 148, and 167 DOF. Feedlot and carcass performance data were analyzed with pen as the experimental unit. Three hundred sixty carcasses (60 carcasses/treatment) were randomly subsampled, and strip loin steaks were aged for 7, 14, and 21 d for assessment of Warner-Bratzler shear force (WBSF) and slice shear force (SSF) with carcass serving as the experimental unit for analysis. No relevant ZH × DOF interactions were detected (P > 0.05). Feeding ZH during the treatment period increased ADG by 9.5%, G:F by 12.5%, carcass ADG by 33.6%, carcass G:F by 35.9%, carcass ADG:live ADG by 15.6%, HCW by 3.2% (345 vs. 356 kg), dressing percent by 1.5%, and LM area by 6.5% and decreased 12th-rib fat by 5.2% and yield grade (YG) by 0.27 units (P < 0.01). Feeding ZH tended to decrease marbling score (437 vs. 442 units; P = 0.10) and increased WBSF at 7 (4.25 vs. 3.47 kg; P < 0.01), 14 (3.57 vs. 3.05 kg; P < 0.01), and 21 d (3.50 vs. 3.03 kg; P < 0.01). Feeding ZH decreased empty body fat percentage (EBF; 29.7% vs. 30.3%; P < 0.01) and increased 28% EBF adjusted final BW (473.4 vs. 449.8 kg; P < 0.01). Analysis of interactive means indicated that the ZH × 148 DOF group had a similar percentage of USDA Prime, Premium Choice, Low Choice, and YG 1, 2, 3, 4, and 5 carcasses (P > 0.10) and decreased percentage of Select (30.4 vs. 36.6%; P = 0.03) and Standard (0.2 vs. 0.9%; P = 0.05) carcasses compared with the control × 127 DOF group. As a result of ZH shifting body composition, extending the DOF of beef heifers is an effective feeding strategy to equalize carcass grade distributions. This can be accomplished along with sustaining the ZH mediated advantages in feedlot and carcass weight gain.
英国×大陆小母牛（n = 3382；初始 BW = 307 kg）连续屠宰，以确定在育肥日粮上增加天数（DOF）是否可以减轻盐酸齐帕特罗（ZH）对牛肉质量等级和嫩度的负面影响。在完全随机区组设计（36 个栏；6 个栏/处理）中使用了 2 × 3 因子处理安排。在屠宰前 0 和 20 至 22 天，每公斤干物质添加 8.33 毫克盐酸齐帕特罗（ZH），再加上 3 至 5 天的停药期，使小母牛的 DOF 分别为 127、148 和 167 天。使用栏作为实验单位分析肥育和胴体性能数据。随机抽取 360 个胴体（60 个胴体/处理）进行随机亚采样，并对带骨里脊牛排进行 7、14 和 21 天的老化，以评估 Warner-Bratzler 剪切力（WBSF）和切片剪切力（SSF），分析以胴体为实验单位。未检测到相关 ZH × DOF 相互作用（P > 0.05）。在处理期内饲喂 ZH 可提高 ADG 9.5%、G:F 12.5%、胴体 ADG 33.6%、胴体 G:F 35.9%、胴体 ADG:活 ADG 15.6%、HCW 3.2%（345 比 356 kg）、出肉率 1.5%、LM 面积 6.5%，12 肋脂肪减少 5.2%，产肉等级（YG）减少 0.27 个单位（P < 0.01）。饲喂 ZH 会降低大理石花纹评分（437 比 442 分；P = 0.10），并增加 7 天（4.25 比 3.47 kg；P < 0.01）、14 天（3.57 比 3.05 kg；P < 0.01）和 21 天（3.50 比 3.03 kg；P < 0.01）的 WBSF。饲喂 ZH 降低了空体脂肪百分比（EBF；29.7%比 30.3%；P < 0.01），增加了 28% EBF 调整后的最终 BW（473.4 比 449.8 kg；P < 0.01）。交互均值分析表明，ZH × 148 DOF 组的美国农业部 Prime、优质选择、低选择和 YG 1、2、3、4 和 5 胴体比例相似（P > 0.10），而选择比例降低（30.4 比 36.6%；P = 0.03）和标准（0.2 比 0.9%；P = 0.05）胴体比例与对照× 127 DOF 组相比。由于 ZH 改变了身体成分，延长牛肉小母牛的育肥日粮天数是均衡胴体等级分布的有效饲养策略。这可以与维持 ZH 介导的肥育和胴体增重优势同时实现。
