Effects of exercise and oral antioxidant supplementation enriched in (n-3) fatty acids on blood oxidant markers and erythrocyte membrane fluidity in horses

The aim of this study was to investigate in a placebo-controlled field study the effect of a (n - 3)-vitamin supplementation on erythrocyte membrane fluidity (ENIF), oxidant/antioxidant markers and plasmatic omega 3/omega 6 fatty acid ratio (FAR) in 12 eventing horses. Venous blood was sampled at rest before (PRE) and after (POST) a three week treatment period with either the supplement (group S, n = 6) or a placebo (group P, n = 6) as well as after 15 min (POST E15') and 24 h (POST E24h) after a standardised exercise test. The following markers were analysed: EMF, plasma antioxidant capacity of water and lipid soluble components, ascorbic acid, uric acid (UA), glutathione (reduced: GSH, oxidised: GSSG), vitamin E (Vit E), beta-carotene, glutathione peroxidase (GPx) and superoxide dismutase (SOD) activity, selenium, copper (Cu), zinc (Zn), oxidised proteins (Protox), lipid peroxides (Pool) and FAR. EMF did not differ between group S and P after treatment, but GPx remained unchanged in group S whereas it decreased in group P and plasma Cu/Zn ratio remained unchanged whereas it increased in group P. FAR were significantly increased in group S. Exercise induced a significant decrease of EMF (POST vs. E24h) in both groups, but which was significantly lower at E15' in group S than in group P. Exercise induced a significant increase of UA and ACW (POST vs. E15') and Protox (POST vs. E24h) in both groups. An exercise-related decrease in GSH and Pool (POST vs. E15') was found in group P, whereas Vit E and FAR (POST vs. E24h) significantly decreased in both groups. The study showed that exercise induced a decrease in ENIF in horses associated with changes of blood oxidative balance. The (omega-3)vitamin supplementation tested improved the oxidative balance poorly but delayed the exercise-induced decrease of EMF and increased the FAR.