U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Journal of Equine Veterinary Science 121 (2023) 104200



U.S. government work


Antioxidant supplementation decreases postexercise oxidative stress but could also decrease muscle pro- tein synthesis. This study compared the effects of three diets: low antioxidant (control, CON), high an- tioxidant (AO), and branched-chain amino acid high antioxidant (BCAO) supplementation on postexercise protein synthesis and oxidative stress. We hypothesized that supplementing antioxidants with branched- chain amino acids(BCAA) would reduce oxidative stress without hindering muscle protein synthesis. Eigh- teen mixed-breed polo horses (11 mares and 7 geldings, with age range between 5 and 18 years, were on CON diet for 30 days (from day -45 until day 0) and then were assigned to one of the treatments after the first lactate threshold test (day 0, LT). LT were also conducted on days 15 and 30 of supplemenation. Ox- idative stress was assessed by measuring blood glutathione peroxidase, superoxide dismutase, and mal- ondialdehyde concentrations before 2 and 4 hours after each LT. Muscle biopsies were taken before and 4 hours after each LT and analyzed for gene expression of protein synthesis by RTqPCR. Data were analyzed by ANOVA and compared by least-square means. A reduction in oxidative stress occurred over time ( P < .05), from day 0 to day 30. An up-regulation in the abundance of muscle protein mRNA transcripts was found for CD36, CPT1, PDK4, MYF5, and MYOG ( P < .05) after all lactate threshold tests, without a treat- ment effect. A treatment-by-exercise effect was observed for MYOD1 ( P = .0041). Transcript abundance was upregulated in AO samples post exercise compared to other treatments. MYF6 exhibited a time-by- treatment effect ( P = .045), where abundance increased more in AO samples from day 0 to day 15 and 30 compared to other treatments. Transcript abundance for metabolic and myogenic genes was upreg- ulated in post exercise muscle samples with no advantage from supplementation of antioxidants with branched-chain amino acids compared to antioxidants alone.