Angus-cross steers (n = 144; 359 kg ± 13.4) were used to assess the effect of dietary Mn and steroidal implants on performance, TM status, hepatic enzyme activity, hepatic gene expression, and serum metabolites. Steers (n = 6/pen) were stratified by BW in a 3 × 2 factorial. GrowSafe bunks recorded individual feed intake (experimental unit = steer; n = 24/treatment). Dietary treatments included (MANG; 8 pens per treatment; Mn as MnSO4): 1) no supplemental Mn (analyzed 14 mg Mn/kg DM; Mn0); 2) 20 mg supplemental Mn/kg DM (Mn20); 3) 50 mg supplemental Mn/kg DM (Mn50). Within MANG, steers received a steroidal implant treatment (IMP) on d 0: 1) no implant; NO; or 2) combination implant (Revalor-200; REV). Liver biopsies for TM analysis and qPCR, and blood for serum glucose, insulin, non-esterified fatty acids (NEFA), and urea-N (SUN) analysis were collected on d 0, 20, 40, and 77. Data were analyzed as a randomized complete block with a factorial arrangement of treatments including fixed effects of Mn treatment (MANG) and implant (IMP) using PROC MIXED of SAS 9.4 using initial BW as a covariate. Liver TM, serum metabolite, enzyme activity, and gene expression data were analyzed as repeated measures. No MANG × IMP effects were noted (P ≥ 0.12) for growth performance or carcass characteristic measures. Dietary Mn did not influence final body weight (FBW), overall ADG, or overall G:F (P ≥ 0.14). Liver Mn concentration increased with supplemental Mn concentration (MANG; P = 0.01). An IMP × DAY effect was noted for liver Mn (P = 0.01) where NO and REV were similar on d 0 but NO cattle increased liver Mn from d 0 to 20 while REV liver Mn decreased. Relative expression of MnSOD in the liver was greater in REV (P = 0.02) compared to NO and within a MANG × IMP effect (P = 0.01) REV increased liver MnSOD activity. These data indicate current NASEM Mn recommendations are adequate to meet demands of finishing beef cattle given a steroidal implant. Despite the roles of Mn in metabolic pathways and antioxidant defense, a basal diet containing 14 mg Mn/kg DM was sufficient for normal growth of finishing steers. This study also provided novel insight into how implants and supplemental Mn influence genes related to arginine metabolism, urea synthesis, antioxidant capacity, and TM homeostasis as well as arginase and MnSOD activity in hepatic tissue of beef steers.

中文翻译：

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类固醇植入物和硫酸锰补充对饲养场公牛生长性能、微量矿物质状态、肝基因表达、肝酶活性和循环代谢物的影响

安格斯杂交公牛（n = 144；359 kg ± 13.4）用于评估膳食锰和类固醇植入物对性能、TM 状态、肝酶活性、肝基因表达和血清代谢物的影响。公牛（n = 6/栏）按体重按 3 × 2 阶乘进行分层。GrowSafe 床位记录了个体采食量（实验单位 = 公牛；n = 24/处理）。饮食治疗包括（MANG；每次治疗 8 栏；Mn 以 MnSO4 形式）： 1) 不补充 Mn（分析为 14 mg Mn/kg DM；Mn0）；2) 20毫克补充锰/公斤DM (Mn20)；3) 50 mg 补充 Mn/kg DM (Mn50)。在 MANG 中，公牛在第 0 天接受类固醇植入治疗 (IMP)：1) 无植入；不; 或 2) 组合植入物 (Revalor-200；REV)。在第 0、20、40 和 77 天收集肝脏活检用于 TM 分析和 qPCR，并收集血液用于血清葡萄糖、胰岛素、非酯化脂肪酸 (NEFA) 和尿素-N (SUN) 分析。数据分析如下使用 SAS 9.4 的 PROC MIXED 并使用初始 BW 作为协变量，对治疗进行因子排列的随机完整块，包括 Mn 治疗 (MANG) 和植入 (IMP) 的固定效应。肝脏TM、血清代谢物、酶活性和基因表达数据作为重复测量进行分析。对于生长性能或胴体特征指标，未发现 MANG × IMP 效应 (P ≥ 0.12)。膳食锰不影响最终体重 (FBW)、总体 ADG 或总体 G:F (P ≥ 0.14)。肝脏锰浓度随着锰浓度的补充而增加（MANG；P = 0.01）。肝脏 Mn 存在 IMP × DAY 效应（P = 0.01），其中 NO 和 REV 在第 0 天相似，但 NO 牛从第 0 天到第 20 天增加肝脏 Mn，而 REV 肝脏 Mn 降低。与 NO 相比，REV 中 MnSOD 在肝脏中的相对表达量更高 (P = 0.02)，并且在 MANG × IMP 效应中 (P = 0.01) REV 增加了肝脏 MnSOD 活性。这些数据表明，当前的 NASEM 锰建议足以满足接受类固醇植入的育肥肉牛的需求。尽管锰在代谢途径和抗氧化防御中发挥作用，但含有 14 毫克锰/千克干物质的基础日粮足以满足育肥公牛的正常生长。这项研究还提供了新的见解，了解植入物和补充锰如何影响与精氨酸代谢、尿素合成、抗氧化能力和TM稳态以及牛肉肝组织中精氨酸酶和MnSOD活性相关的基因。