Effect of different levels of amino acids and feeding methods on growth performance and immune responses in broiler chickens

The objective of this study was to investigate the effects of different levels of amino acid and feeding methods on performance and immune system of broiler chickens. Experimental design was based on completely randomized design in a factorial arrangement with 3 feeding methods [control (ad libitum feed intake)، intermittent feeding (IF) and continuous feed withdrawal (FW))، and 2 amino acid levels (level recommended by Arian and 8 % more). Each treatment was replicated 6 times with 23 male broilers per replicate. The CFW method was associated with a decreased mortality rate (P<0. 05). The IF and FW methods improved feed conversion ratio (P<0. 05). In CFW and IF feeding programs، the relative weight of spleen was increased (P<0. 05). At higher amino acid level، the percentage of circulatory lymphocyte was decreased and that of heterophil and heterophil to lymphocyte ratio were increased (P<0. 05). In conclusion، it seems that the FW feeding regimen with Arian recommended amino acid level might have a positive effect on the cellular but not the humeral immune system with no adverse effect on growth performance.