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

Abstract

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 triplicate with10 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 <em>ad libitum</em> with free access to water throughout the entire experiment. Inclusion of aflatoxin in the feed at 0.5mg/kg feed caused a significant reduction in the growth performance of broilers. Supplementation of melatonin (20mg/kg in feed and 20mg/kg body weight through <em>i.p.</em> route) or its precursor (L-tryptophan at 250 mg/kg feed) in aflatoxin fed broilers resulted in numerically improved performance. 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 wereobserved among various groups with respect to kidney and spleen weight but liver weight increased significantly (P≤0.05) and weight of bursa significantly decreased upon aflatoxin inclusion. Our study suggests that L-tryptophan was partially as effective as melatonin in alleviating aflatoxin induced growth retardation and immunosuppression in broiler chicken.