Department of Animal Sciences, Auburn University, Auburn, AL, United States of America.
PLoS One. 2020 Jul 2;15(7):e0235481. doi: 10.1371/journal.pone.0235481. eCollection 2020.
In general, beef cattle long-distance transportation from cow-calf operations to feedlots or from feedlots to abattoirs is a common situation in the beef industry. The aim of this study was to determine the effect of rumen-protected methionine (RPM) supplementation on a proposed gene network for muscle fatigue, creatine synthesis (CKM), and reactive oxygen species (ROS) metabolism after a transportation simulation in a test track. Angus × Simmental heifers (n = 18) were stratified by body weight (408 ± 64 kg; BW) and randomly assigned to dietary treatments: 1) control diet (CTRL) or 2) control diet + 8 gr/hd/day of top-dressed rumen-protected methionine (RPM). After an adaptation period to Calan gates, animals received the mentioned dietary treatment consisting of Bermuda hay ad libitum and a soy hulls and corn gluten feed based supplement. After 45 days of supplementation, animals were loaded onto a trailer and transported for 22 hours (long-term transportation). Longissimus muscle biopsies, BW and blood samples were obtained on day 0 (Baseline), 43 (Pre-transport; PRET), and 46 (Post-transport; POST). Heifers' average daily gain did not differ between baseline and PRET. Control heifer's shrink was 10% of BW while RPM heifers shrink was 8%. Serum cortisol decreased, and glucose and creatine kinase levels increased after transportation, but no differences were observed between treatments. Messenger RNA was extracted from skeletal muscle tissue and gene expression analysis was performed by RT-qPCR. Results showed that AHCY and DNMT3A (DNA methylation), SSPN (Sarcoglycan complex), and SOD2 (Oxidative Stress-ROS) were upregulated in CTRL between baseline and PRET and, decreased between pre and POST while they remained constant for RPM. Furthermore, CKM was not affected by treatments. In conclusion, RPM supplementation may affect ROS production and enhance DNA hypermethylation, after a long-term transportation.
一般来说，从奶牛养殖到饲养场或从饲养场到屠宰场的肉牛长途运输是牛肉行业的常见情况。本研究的目的是确定在运输模拟试验中添加瘤胃保护性蛋氨酸（RPM）对肌肉疲劳、肌酸合成（CKM）和活性氧（ROS）代谢的拟议基因网络的影响。 Angus ×西门塔尔小母牛（n = 18）按体重（408 ± 64 kg；BW）分层，并随机分配到以下饮食处理组：1）对照饮食（CTRL）或 2）对照饮食+ 8 克/头/天瘤胃保护性蛋氨酸（RPM）。在适应 Calan 门后，动物接受了上述饮食处理，即自由采食百慕大干草和基于大豆皮和玉米面筋饲料的补充饲料。在补充 45 天后，动物被装载到拖车上，并运输 22 小时（长途运输）。在第 0 天（基线）、43 天（运输前；PRET）和 46 天（运输后；POST）采集背最长肌活检、BW 和血液样本。与基线相比，PRET 时对照小母牛的日增重没有差异。对照小母牛的体重减轻了 10%，而 RPM 小母牛的体重减轻了 8%。血清皮质醇降低，葡萄糖和肌酸激酶水平在运输后升高，但处理之间没有差异。从骨骼肌组织中提取信使 RNA，并通过 RT-qPCR 进行基因表达分析。结果表明，在 CTRL 中，AHCY 和 DNMT3A（DNA 甲基化）、SSPN（Sarcoglycan 复合物）和 SOD2（氧化应激-ROS）在基线和 PRET 之间上调，并在 PRET 和 POST 之间下调，而 RPM 则保持不变。此外，CKM 不受处理影响。综上所述，RPM 补充可能会影响 ROS 的产生并增强 DNA 超甲基化，尤其是在长途运输后。
