effect of dietary melatonin and l-tryptophan on growth performance and immune responses ofbroiler 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 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 ad libitum 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 i.p. 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.