Carcass characteristics and breast meat quality in fast-, medium- and slow-growing chickens

The aim of the present study was to compare carcass characteristics and meat quality of fast- (Ross 308), medium- (Hubbard JA757) and slow-growing (ISA Dual) chickens (n = 1 980). When the chickens reached an average live weight of 2 kg, 40 birds (males to females, 1 : 1) of each genotype were randomly selected and slaughtered for carcass analysis. Pectoralis major (PM) muscle samples were taken to determine the physical and chemical parameters of the meat quality. The fast- and medium-growing genotypes had higher (+3.24% and +3.84%, respectively) dressing out percentages than the slow-growing chickens. As expected, the breast percentage significantly decreased in the order of fast growth > medium growth > slow growth. The abdominal fat percentage was the lowest in Ross 308 chickens, but the abdominal fat percentage in JA757 and ISA Dual chickens did not differ. For edible organs, fast- and medium-growing chickens had heavier hearts and livers than slow-growing chickens. In contrast, ISA Dual chickens showed heavier gizzards. Genotype dramatically affected the chemical composition of PM muscle. The ISA Dual chickens exhibited a significantly higher proportion of dry matter and protein and lower ether extract and cholesterol content than Ross 308 chickens, with intermediate values for JA757 chickens. The ISA Dual group had a lower ash content than Ross 308 and JA757 groups. In terms of physical parameters, the ISA Dual chickens had higher lightness and yellowness and lower redness, pH 24, and cooking loss than those of the other genotypes. Concerning all genotypes, the shear force values increased from fast- to slow-growing chickens. In conclusion, this study found a difference between the genotypes. Although the slow-growing chickens showed the lowest dressing out and breast percentages compared with the other genotypes, the breast meat of the slow-growing chickens had more favourable nutritional properties.