Inheritance of carcass variables when giant jungle fowl and broilers achieve a common physiological body weight

Ten chicks each from Giant Jungle Fowl (JF), broiler breeders (BB), and the respective F1 cross between them, were reared under typical broiler management practices until they reached a market weight of approximately 1,818 g. When individual birds reached market weight they were killed by CO2 asphyxiation and variables (length and weight) associated with organ, muscle, and skeletal growth were measured. Age to market weight demonstrated parental and heterotic effects. The JF had more deboned leg muscle and less Pectoralis major muscle than BB. Abdominal fat was higher in BB and showed positive heterosis. Organ weights were consistently lower for JF than BB. Positive heterosis was observed for spleen and pancreas, and negative heterosis was indicated for heart, liver, and lung. The digestive tract generally weighed less and was shorter in length for JF than for BB. Positive heterosis was observed for proventriculus and gizzard weight, and negative heterosis was noted for duodenum and jejunum lengths. Parental line differences were observed for most bone variables, including weight and length. Parental lines differed for femur breaking strength, but not for tibiotarsus breaking strength. A large negative heterotic effect was observed for tibiotarsus bone breaking strength.