The impact of age and exercise on antioxidants and oxidative stress in horses.

The present study examined the effect of acute exercise and intensive exercise training on the oxidative stress, antioxidant status, and muscle metabolism of yearlings and mature mares. Objective one was to look at the effect of repeated biopsies on muscle inflammation and oxidative stress. The pattern of biopsies does impact oxidative stress occurrence, with an alternating corner pattern resulting in less oxidative stress than biopsies taken in a row. Objective two was to look at levels of oxidative stress and antioxidants in the blood and skeletal muscle of horses after an acute bout of exercise. It was found that some markers were affected by acute exercise, but overall the test was not sufficient to induce severe oxidative stress, thus the intensity of acute exercise does impacts the level of oxidative stress endured by the horse. Objective three was to compare the effects of exercise training on oxidative stress and antioxidant status between yearlings and mares. It was found that training did significantly improve antioxidant status and reduce oxidative stress in the trained mares, while the trained yearlings did not have as significant changes in either regard. Objective four was to compare the effects of acute exercise before and after exercise training on oxidative stress, antioxidants, cortisol, and creatine kinase in two yearlings and mares. When challenged to acute exercise before training the mares had significantly higher levels of oxidative stress and cortisol and lower antioxidant status as compared to the yearlings. After exercise training, trained mature mares had lower levels of oxidative stress compared to prior training, and when challenged to acute exercise had lower oxidative stress and cortisol. The yearlings had few significant changes in oxidative stress after training and in response to acute exercise. In conclusion, young, maturing horses had lower levels of oxidative stress and cortisol, and higher levels of antioxidants, as compared to mature mares. Training can help reduce levels of oxidative stress in mature mares, while in young horses training is not as influential in reducing oxidative stress, suggesting that their young age is the most important defense against exercise-induced oxidative stress.Ph. D.Includes bibliographical referencesby Danielle Nicole Smars