Abstract
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.
Highlights
Long-distance road transportation (> 400 km) is a stressful event that most cattle experience at least once in their lifetime [1]
Body weight did not present a treatment × time interaction (P = 0.44), it showed a decrease after transportation in CTRL and rumen-protected methionine (RPM) heifers (P < 0.01) (Fig 3)
Serum glucose, creatine kinase and cortisol levels were not affected by the administration of RPM, suggesting that the catalytic processes generated due to high stress level could not be diminished by a greater methionine availability
Summary
Long-distance road transportation (> 400 km) is a stressful event that most cattle experience at least once in their lifetime [1]. Several research studies have been conducted in the last few decades, in an effort to achieve a better understanding of the characteristics of road transportation and its effects on cattle [3,4,5,6]. Analysis of these effects will improve animal welfare and help reduce the economic losses associated with transportation [7]. Muscle fatigue manifests as an inability to continue a motor task at the required intensity, eventually leading to exhaustion [10]
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