Effects of Daily Astaxanthin and L-Carnitine Supplementation for Exercise-Induced Muscle Damage in Training Thoroughbred Horses

• The effect of providing oral supplementation with an antioxidant astaxanthin and L-carnitine on serum markers of exercise-induced muscle damage in horses was examined.
• The CK activity was significantly lower in supplemented versus control groups.
• The incidence of lameness with muscle pain was also significantly lower in supplemented horses.
• Administrating astaxanthin and L-carnitine supplement might be helpful in maintaining condition and performance for exercising horses.

The effects of dietary supplementation with astaxanthin and L-carnitine on serum markers and clinical incidence rate of exercise-induced muscle damage were studied in training horses. Sixty-three healthy Thoroughbred horses were randomly assigned to two groups and received the same base diet and exercise training throughout this study. The supplement (supp.) group (n = 31) received daily supplementation with astaxanthin (75 mg) and L-carnitine (3,000 mg) for 8 weeks, and the control (cont.) group (n = 32) received no supplementation. Blood samples were collected after high-intensity exercise training at 5 weeks before supplementation, 3 days (3d), and 8 weeks (8w) after the start of the supplementation. The blood samples were analyzed for creatine kinase (CK) activity and lactate dehydrogenase isoenzyme-5 (LDH-5), and a retrospective study was carried out by analyzing medical records for symptoms of exercise-induced muscle damage in both groups. Five horses (two of supp. group and three of cont. group) were excluded from this study for other disease. In the cont. group, CK activity at 8w was significantly increased compared with 3d, whereas the supp. group showed no significant change. After 8w, the CK activity of the supp. group was significantly lower than that of the cont. group. Additionally, the LDH-5 concentration of the supp. group also tended to be lower as compared with that of the cont. group. The incidence rate of exercise-induced muscle damage was significantly lower in the supp. group compared with the cont. group. These results suggest that continuous dietary administration of astaxanthin and L-carnitine attenuates exercise-induced muscle damage in horses.