Effect of Valine Supplementation on Growth Performance, Immune Response, Blood Metabolites and Behavioral Indices of Broiler Chickens Exposed to Heat Stress

The effects of valine supplementation on performance, immunity and behavioural indices of broiler chickens under heat stress condition was evaluated. Total of 420 male and female Ross-308 broiler chickens were allocated to 6 treatments with 5 replicates in a completely randomized design. Experimental groups were as fallows: positive control (fed basal diet and reared under Ross-308 recommended rearing temperature), nagative control (fed basal diet and reared under heat stress (HS)), and four treatment groups fed basal diet supplemented with 5, 10, 15 and 20% valine above the Ross-308 valine recommendation and reared under HS. Heat stress significantly decreased feed intake, body weight and European production efficiency factor (EPEF), antibody titer against NewCastle, lymphocyte percentage, serum total protein concentration and alkaline phosphatase and lactate dehydrogenase activities and increased heterophile percentage, heterophile to lymphocyte ratio, rectal temperature and tunic immobility of broiler chickens (P< 0.05). Supplementation  of5% valine improved BW of broiler chicken at the end of grower and BW and EPEF at the end of total period. Addition of  10% valine increased relative weight of breast and thigh muscle and 15 and 20% valine supplementation increased lymphocyte and decreased heterophile percentage as compared to control group (P< 0.05). In conclusion, 5% valine supplementation improved final body weight and feed convertion ratio of heat-stressed broiler chikens and 15 and 20% valin inclusion improved blood immune cell percentages but had no effect on humoral immune response and tunic immobility test of HS broiler chickens.