Effect of Dietary Melatonin and L-Tryptophan on Growth Performance and Immune Responses of Broiler Chicken under Experimental Aflatoxicosis

The aim of the present work was to determine whether the administration of melatonin or L -tryptophan (a precursor of melatonin) affects the immune responses and performance of broilers during induced exposure to aflatoxins in feed. The study was conducted from 0-6 weeks comprising six dietary treatments in tripli-cate with 10 chickens in each replicate. The diets were formulated to supply 23% crude protein (CP) and 2800 kcal ME/kg in starter ration and 20% CP and 2900 kcal ME/kg in finisher ration. The experimental diets were offered ad libitum with free access to water throughout the entire experiment. Inclusion of afla-toxin in the feed at 0.5 mg/kg feed caused a significant reduction in the growth performance of broilers. Supplementation of melatonin (20 mg/kg in feed and 20 mg/kg body weight through i.p. route) or its pre-cursor (L-tryptophan at 250 mg/kg feed) in aflatoxin fed broilers resulted in numerically improved perform-ance. Aflatoxin inclusion in the feed also caused a significant reduction in haemagglutination titer against sheep RBC and cell mediated immune responses to phytohemagglutinin (PHA-P) in broilers. Melatonin or L-tryptophan inclusion in toxin incorporated feed significantly improved both humoral and cell mediated immunity. No significant (P > 0.05) differences were observed among various groups with respect to kidney and spleen weight but liver weight increased significantly (P?0.05) and weight of bursa significantly de-creased upon aflatoxin inclusion. Our study suggests that L-tryptophan was partially as effective as mela-tonin in alleviating aflatoxin induced growth retardation and immunosuppression in broiler chicken.