Influence of exercise and dietary omega-3 oil supplementation on interleukin 1-Ra serum concentrations in Standardbred horses

In this study, the influence of fish oil eicosapentaenoic acid and docosahexaenoic acid supplementation on serum interleukin-1 receptor antagonist (IL-1Ra) concentrations was evaluated in horses subjected to a regular racing program. IL-1Ra is an anti-inflammatory protein. It binds to IL-1 receptors blocking the attachment of pro-inflammatory cytokines. Ten regularly trained Standardbred horses (6 geldings and 4 mares, 4-5 years old, mean bodyweight 500 ± 25 kg) were used. They were randomly divided in two equal groups. The experimental group received a supplementation of 70 mL of fish oil (Omega Horse NBF Lanes, Milan, Italy) every day for 30 days. The control group did not receive any food supplement. Every 10 days (T0, T10, T20 and T30), the horses took part in a 1600-m harness race, and blood samples were collected from each horse before the race and after the race for the measurement of IL-1Ra serum concentration. The application of general linear model-multivariate analysis of variance (ANOVA) showed an effect of race and dietary supplementation. The effect of race on serum IL-1Ra concentrations was observed starting from T20. In particular, serum IL-1Ra showed higher values after the race in both groups at T20 whereas at T30, serum IL-1Ra values increased in the control group and decreased in the experimental group. The results obtained in the present study suggest that submaximal exercise induces an increase of IL-1Ra serum concentration after 20 days of a racing program. Fish oil supplementation had a positive effect on post-exercise response of serum IL-1Ra concentration compared with the unsupplemented control group, suggesting dietary fish oil reduces the response to inflammatory processes induced by physical activity.