Department of Animal Sciences, Colorado State University, Fort Collins 80523-1171, USA.
J Anim Sci. 2010 Dec;88(12):4102-19. doi: 10.2527/jas.2010-2901. Epub 2010 Aug 20.
Two experiments were conducted to evaluate effects of ractopamine (RAC) and steroidal implant treatments on performance, carcass traits, blood metabolites, and lipogenic enzyme activity in feedlot cattle. In Exp. 1, yearling steers (n = 486; initial BW = 305 kg) were used in a 3 × 3 factorial arrangement of RAC doses of 0 (R0), 100 (R100), or 200 (R200) mg·steer(-1)·d(-1) fed for 28 d and implant regimens (implant-reimplant) of no implant-no reimplant (NI-NI), 120 mg of trenbolone acetate (TBA) and 24 mg of estradiol-17β (E17B)-no implant (RS-NI), or 80 mg of TBA and 16 mg of E17B followed by 120 mg of TBA and 24 mg of E17B (RI-RS). Except for KPH and skeletal maturity score, no RAC × implant interactions were noted (P > 0.10). Carcasses from R200 were 6.3 kg (P = 0.042) heavier than those from R0. Marbling, calculated empty body fat (EBF), and USDA quality grade did not differ (P > 0.10) among RAC treatments. The RI-RS steers had 12.6 kg (P = 0.001) and 41.1 kg (P < 0.001) greater HCW than RS-NI and NI-NI, respectively. Despite no difference (P > 0.10) in EBF, marbling score was decreased for RI-RS (P < 0.001) and RS-NI (P = 0.001) relative to NI-NI, resulting in 14.6 and 11.4 percentage unit fewer USDA Prime and Choice carcasses with RI-RS (P = 0.008) and RS-NI (P = 0.039) than with NI-NI. In Exp. 2, heifers (n = 48; initial BW = 347 kg) were used in a 3 × 2 factorial arrangement of RAC doses of 0 (R0) or 250 (R250) mg·heifer(-1)·d(-1) and implant regimens of none (NI), 200 mg of TBA (TO), or 200 mg of TBA and 20 mg of E17B (TE). Blood samples were collected at various times during the feeding period, and subcutaneous adipose samples were collected on d 119. For growth and carcass measurements, no RAC × implant interactions (P > 0.10) were detected. The RAC-supplemented heifers had greater HCW (P < 0.10) with no difference in marbling score. For implant regimens, TE heifers had greater HCW than the NI (P = 0.001) and TO (P = 0.037) heifers. Although EBF did not differ among implant treatments (P > 0.10), TE (P = 0.021) and TO (P = 0.039) had fewer Choice carcasses than NI. Heifers with implants had decreased cortisol and increased IGF-1 and NEFA (P < 0.10) compared with NI heifers. An implant × RAC interaction was detected (P = 0.001) for serum urea nitrogen (SUN), with TE and RAC-supplemented heifers having decreased SUN. These data suggest that the effects of implant and RAC on growth and carcass traits are independent and that USDA quality grade and marbling score can differ significantly among carcasses with similar calculated EBF values.
两项实验旨在评估莱克多巴胺（RAC）和甾体植入物对育肥牛的性能、胴体特性、血液代谢物和脂肪生成酶活性的影响。在实验 1 中，使用了 486 头一岁大的阉牛（初始体重为 305 千克），采用 RAC 剂量为 0（R0）、100（R100）或 200（R200）mg·头-1·d-1 的 3×3 因子设计，并进行 28 天的饲养，植入方案为无植入物-无再植入（NI-NI）、120mg 群勃龙醋酸酯（TBA）和 24mg 雌二醇-17β（E17B）-无植入物（RS-NI）或 80mg TBA 和 16mg E17B 随后是 120mg TBA 和 24mg E17B（RI-RS）。除了 KPH 和骨骼成熟评分外，RAC×植入物之间没有观察到相互作用（P＞0.10）。R200 组的胴体比 R0 组重 6.3 千克（P=0.042）。大理石花纹、计算的空体脂肪（EBF）和 USDA 质量等级在 RAC 处理之间没有差异（P＞0.10）。RI-RS 组的 HCW 比 RS-NI 组和 NI-NI 组分别高出 12.6 千克（P=0.001）和 41.1 千克（P＜0.001）。尽管 EBF 没有差异（P＞0.10），但 RI-RS 组和 RS-NI 组的大理石花纹评分分别下降（P＜0.001），导致 RI-RS 组和 RS-NI 组的 USDA 优质和选择等级胴体分别比 NI-NI 组少 14.6 和 11.4 个百分点（P=0.008）和（P=0.039）。在实验 2 中，使用了 48 头小母牛（初始体重为 347 千克），采用 RAC 剂量为 0（R0）或 250（R250）mg·头-1·d-1 的 3×2 因子设计，并进行无植入物（NI）、200mg TBA（TO）或 200mg TBA 和 20mg E17B（TE）的植入方案。在饲养期间的不同时间采集血液样本，并在第 119 天采集皮下脂肪样本。对于生长和胴体测量，没有发现 RAC×植入物相互作用（P＞0.10）。补充 RAC 的小母牛的 HCW 更高（P＜0.10），但大理石花纹评分没有差异。对于植入方案，TE 组的 HCW 比 NI（P=0.001）和 TO（P=0.037）组更高。尽管植入物处理之间的 EBF 没有差异（P＞0.10），但 TE（P=0.021）和 TO（P=0.039）的选择等级胴体比 NI 组少。与 NI 组小母牛相比，植入物组的小母牛的皮质醇降低，IGF-1 和 NEFA 增加（P＜0.10）。血清尿素氮（SUN）检测到植入物×RAC 相互作用（P=0.001），TE 和 RAC 补充组的 SUN 降低。这些数据表明，植入物和 RAC 对生长和胴体特性的影响是独立的，并且 USDA 质量等级和大理石花纹评分可以在具有相似计算 EBF 值的胴体之间有明显的差异。
