This study aimed to study the effects of delayed placement (IA) and dietary lysine levels (LD) in initial diets on breast muscle development and carcass yield of broiler chickens. For this, 1,760 male Cobb500 chicks were allocated randomly to eight experimental groups according to a 2x4 factorial arrangement for 4 IAs (12, 24, 36 and 48h) and 2 levels of LD (1.143 and 1.267%) with four replicates and 55 chicks per experimental unit. Met+Cys, Thr and Trp were balanced according to the ideal protein concept. There were no significant interactions between LD and IA on variables evaluated. The highest breast weight and breast fillet weight at 21 days old and body weight at 43 days old were obtained with the dietary lysine level of 1.143%. The breast weight, breast fillet weight and muscle fiber diameter at 21 days old, body weight, carcass weight and legs weight at 43 days old decreased linearly according to the increase of the delayed placement. The results of this study suggest that the 1.143% DL level improves the breast muscle development at 21 days old and chicken body weight at 43 days old, and the shortest delayed placement improves the breast muscle development during the initial phase and higher carcass yield and legs at the slaughter.
breast fillet; muscle development; protein:DNA ratio; satellite cells; starvation
