Department of Animal Science, Iowa State University, Ames, IA 50011, USA.
Department of Animal, Dairy and Veterinary Science, Utah State University, Logan, UT 84322, USA.
J Anim Sci. 2024 Jan 3;102. doi: 10.1093/jas/skae154.
Angus-cross steers (n = 144; 362 kg ± 20.4) were used to determine the effect of Zn and steroidal implants on performance, trace mineral status, circulating metabolites, and transcriptional changes occurring in skeletal muscle. Steers (n = 6 per pen) were stratified by body weight (BW) in a 3 × 2 factorial. GrowSafe bunks recorded individual feed intake (steer as experimental unit; n = 24 per treatment). Dietary treatments (ZINC; eight pens per treatment) included supplemental Zn as ZnSO4 at 1) 0 (analyzed 54 mg Zn/kg DM; Zn0); 2) 30 mg/kg DM (Zn30); 3) 100 mg Zn/kg DM (Zn100). After 60 d of Zn treatment, steers received a steroidal implant treatment (IMP) on day 0: 1) no implant; NO; or 2) high-potency combination implant (TE-200, Elanco, Greenfield, IN; 200 mg TBA, 20 mg E2; TE200). BWs were taken at days -60, 0, and in 28 d increments thereafter. Liver biopsies for TM analysis and blood for TM, serum glucose, insulin, nonesterified fatty acids (NEFA), urea-N, and IGF-1 analysis were collected on days 0, 20, 40, and 84. Glucose, NEFA, and insulin were used to calculate the revised quantitative insulin sensitivity check index (RQUICKI). Linear and quadratic effects of ZINC were evaluated in SAS 9.4. Means for IMP were separated using the LSMEANS statement with the PDIFF option. Day -60 BW was a covariate for performance and carcass data. Growth performance, plasma, liver, and metabolite data were analyzed as repeated measures. TE200 tended to decrease plasma Zn by 8.4% from days 0 to 20 while NO decreased by 3.6% (IMP × day; P = 0.08). A tendency for a ZINC × day effect on G:F was noted (P = 0.06) driven by Zn30 and Zn100 decreasing significantly from period 0-28 to period 28-56 while Zn0 was similar in both periods. An IMP × day effect was noted for RQUICKI where (P = 0.02) TE200 was greater on day 40 compared to NO cattle, but by day 84 RQUICKI was not different between TE200 and NO. On day 20, increasing Zn supplementation linearly increased mRNA abundance (P ≤ 0.09) of protein kinase B (AKT1), mammalian target of rapamycin (mTOR), matrix metalloproteinase 2 (MMP2), and myogenic factor 5 (MYF5). In this study, Zn and implants differentially affected genes related to energy metabolism, satellite cell function, and TM homeostasis on days 20 and 84 postimplant. These results suggest steroidal implants increase demand for Zn immediately following implant administration to support growth and may influence insulin sensitivity in finishing cattle.
Angus-cross 阉牛（n=144；362kg±20.4）用于确定 Zn 和甾体植入物对性能、痕量矿物质状态、循环代谢物和骨骼肌转录变化的影响。牛（每栏 6 头）按体重（BW）进行 3×2 析因。GrowSafe 卧床记录了个体采食量（以牛为实验单位；每处理 24 头）。日粮处理（ZINC；每处理 8 个栏）包括 1）0（分析 54mg Zn/kg DM；Zn0）；2）30mg/kg DM（Zn30）；3）100mg Zn/kg DM（Zn100）的额外 Zn。在 Zn 处理 60d 后，牛在第 0 天接受了甾体植入物处理（IMP）：1）无植入；NO；或 2）高活性组合植入物（TE-200，Elanco，Greenfield，IN；200mg TBA，20mg E2；TE200）。在-60、0 和此后 28d 增量时测量 BW。在第 0、20、40 和 84d 时采集肝活检用于 TM 分析和血液用于 TM、血清葡萄糖、胰岛素、非酯化脂肪酸（NEFA）、尿素-N 和 IGF-1 分析。使用修订后的定量胰岛素敏感检查指数（RQUICKI）计算葡萄糖、NEFA 和胰岛素。在 SAS 9.4 中评估 ZINC 的线性和二次效应。使用 LSMEANS 语句和 PDIFF 选项分离 IMP 的均值。第-60d BW 是性能和胴体数据的协变量。生长性能、血浆、肝脏和代谢物数据作为重复测量进行分析。在第 0-20d 时，TE200 有降低血浆 Zn 8.4%的趋势，而 NO 降低了 3.6%（IMP×天；P=0.08）。注意到 G:F 有 ZINC×天的效应（P=0.06），这是由于 Zn30 和 Zn100 在 0-28d 至 28-56d 期间显著下降，而 Zn0 在两个时期相似。IMP×天对 RQUICKI 有影响（P=0.02），在第 40d 时 TE200 比 NO 牛高，但在第 84d 时 TE200 和 NO 之间的 RQUICKI 没有差异。在第 20d 时，随着 Zn 补充量的增加，蛋白激酶 B（AKT1）、雷帕霉素靶蛋白（mTOR）、基质金属蛋白酶 2（MMP2）和肌生成因子 5（MYF5）的 mRNA 丰度呈线性增加（P≤0.09）。在本研究中，Zn 和植入物在植入后第 20 和 84d 时对与能量代谢、卫星细胞功能和 TM 稳态相关的基因产生了不同的影响。这些结果表明，甾体植入物在植入后立即增加对 Zn 的需求，以支持生长，并可能影响育肥牛的胰岛素敏感性。
