LAUSR

Different participants generally located distant among them compose the U.S. beef production chain, therefore shipping is required for cattle at least once in their lifespan. The aim of this study was to determine the effect of Rumen-Protected Methionine (RPM) supplementation on muscle fatigue gene network, creatine synthesis (CKM), and Reactive Oxygen Species (ROS) metabolism after a transportation simulation in a 1.7-miles oval test track. Angus heifers (n = 18) were stratified by body weight (408 ± 64 kg; BW) and randomly assigned to dietary treatments: 1) control diet (CTRL), and 2) control diet + rumen-protected methionine (RPM). After a successful adaptation period to Calan gates, animals received a common diet of Bermuda hay ad libitum and a soy hulls and corn gluten feed based supplement. After 45 days under supplementation, animals were loaded onto a 32 × 7 ft. trailer and transported for 22 hours. Skeletal muscle biopsies, BW and blood samples were obtained on day 0 (Baseline), 43 (Pre-transport, “PRET”), and 45 (Post-transport, “POST”). Heifer’s average daily gain did not differ between Baseline and PRET (P = 0.41). Control heifer’s shrink was 8% of BW while RPM heifers shrink was 10% (P = 0.29). Cortisol level decreased after transportation, but no differences were observed between treatments (P = 0.94). Messenger RNA was extracted from skeletal muscle tissue and gene expression analysis was performed by RT-qPCR. Results showed that AHCY (Creatine synthesis pathway), SSPN (Sarcoglycan complex), DNMT3A (DNA Methylation), and SOD2 (Oxidative Stress-ROS) were upregulated (P < 0.05) in CTRL between baseline and PRET and, decreased between PRET and POST (P < 0.05) while they remained constant for RPM. Furthermore, CKM was not affected by treatments (P = 0.11). In conclusion, muscle fatigue related genes were not affected by RPM. Although, RPM could affect ROS production, after a long-term transportation.