Effects of dietary fumaric acid on the growth performance, immune response, relative weight and antioxidant status of immune organs in broilers exposed to chronic heat stress

This study aimed to investigate the effects of dietary fumaric acid (FA) on growth performance, immune responses, immune organ index and antioxidant status in broilers under chronic heat stress (HS). A total of 200 21-day-old Ross 308 chicks were randomly assigned in a 2 × 2 factorial arrangement with two diets (basal diet or 10 g/kg FA diet) and two temperatures (thermoneutral or HS) for 21 days. On day 42, growth performance, immune organ index, immune function and antioxidative ability were determined. HS resulted in a significant reduction in final body weight (FBW), average daily feed intake (ADFI), average daily gain (ADG), antibody titres against sheep red blood cells (SRBC) and Newcastle disease virus, IgM, IgG, relative weights of spleen, thymus and bursa of Fabricius, but a significant increase in the feed conversion ratio (FCR), activities of total superoxide dismutase (T-SOD) and glutathione peroxidase (GPx) in the bursa, contents of malondialdehyde and total carbonyl (TC) in thymus and bursa (P < 0.05). Dietary supplementation of FA increased FBW, ADFI, ADG, antibody titres against SRBC, IgG, relative weights of spleen and bursa, activity of GPx in thymus and bursa, whereas it decreased the FCR and TC of thymus and bursa. These results suggest that dietary 10 g/kg FA had positive effects on growth performance and immune function through improving the antioxidative capacity of immune organs.