Effects of breed, sex and diet and their interactions on carcass composition and tissue weight distribution of broiler chickens

Abstract. The effects of breed (Hubbard and Anak), sex and diet (two levels of protein (high or low) with two levels of crude fiber (low or high) at each level of protein) on carcass composition and distribution of tissues over the carcass were studied. Carcass composition and ratios of muscle: bone, muscle: fat and meat: bone in the carcass did not differ significantly between breed groups. Male carcasses had more muscle, more bone, more fat-free carcass, higher ratios of muscle: bone, muscle: fat but less fat, less meat and lower meat: bone ratio than female carcasses. Carcasses of chicks fed high protein (with either low or high fiber) diet had more muscle than carcasses of chicks fed low protein (with either low or high fiber) diet. Carcasses of chicks fed high fiber (with either low or high protein) diet had more bone but less meat than carcasses of chicks fed low fiber (with either low or high protein) diet. Increasing both protein and fiber in the diet resulted in lowering carcass fat, consequently raising muscle: fat ratio. Breed and sex did not influence the distribution of muscle and meat throughout the carcass parts. Breed differences in fat weight distribution were not significant. Anak had significantly higher proportions of bone in wing and neck than Hubbard did. The proportion of total carcass muscle in breast, drumstick, wing were not significantly affected by diet. Carcasses of chicks fed high fiber (with either low or high protein) diet had higher proportion of total meat in thigh and neck than carcasses from chicks fed low fiber (with either low or high protein) diet. Diet had no significant effect on bone weight distribution. Increasing crude fiber in diets resulted in lowering proportion of total fat in breast, thigh but increasing proportion of total fat in drumstick and wing. Breed x sex, breed x diet and sex x diet interactions did not significantly influence most of carcass traits indicating that the factors under consideration act independently of each other's. Significant sex x diet interactions was found for carcass fat and boneless carcass relative to live body weight: the sexual dimorphism in low protein diet is more pronounced than in high protein diets.