Evidence of oxidative stress in horses has been described in reports dealing with intense and endurance exercise. Oxidative stress occurs when antioxidant systems are insufficient causing oxidation to potentially damage DNA, proteins, and lipids, and contribute to degenerative changes. Vitamin E is the most commonly supplemented antioxidant in horses and has been shown that horses in exercise conditioning may require higher intakes of vitamin E than recommended. Also in various species vitamin C potentiates the effects of vitamin E; however, under maintenance conditions horses have the ability to synthesize sufficient ascorbate, the demand increases as stress on the body is increased. Competitive endurance horses were estimated to consume 1.2 to 5-times higher levels of vitamin E than recommended intakes. In these horses a negative correlation was found between the vitamin E intake and creatine kinase, and aspartate aminotransferase. Similarly, three-day event horses have vitamin E average intakes about 50% over recommended levels, and it was also found that intake of vitamin E negatively correlated with inflammatory markers. However, large doses of vitamin E at about 10-times the recommended levels could potentially interfere with beta-carotene absorption. While some studies have shown benefits of lipoic acid supplementation in endurance trained horses similar to that of vitamin E, other studies failed to show any benefit of supplemental superoxide dismutase in intensely exercising horses. The implications from this broad scope of work show potential benefits for supplementing various antioxidants however, before assuming efficacy from other species horse specific studies should be performed.
equine; lipoic acid; oxidative stress; vitamin E
