Differences in carcass composition and meat quality of conventional and slow-growing broiler chickens raised at 2 stocking densities

Abstract

The fast growth rate of broiler chickens is a welfare concern that has increased consumer interest in chicken from slower growing (SG) broilers. Replacing conventional (CONV) broilers with SG broilers will reduce chicken supply and SG broilers require different management practices than CONV. This study evaluated the effects of 2 stocking densities on the carcass composition and meat quality of CONV broilers that reach market weight at 42 d and SG broilers that reach market weight at 63 d. Male broilers from each strain were exclusively stocked into 16 pens at a density of either 29 kg/m2 or 37 kg/m2. Live body, carcass without giblets (WOG), and part weights were recorded and used to calculate yield. Initial and 24-hour pH, color (L*, a*, and b*), cooking loss, and Warner Bratzler shear force of the breast and thigh muscles were measured. Birds from both strains reached similar live body and carcass WOG weights. CONV had 3.4%, 13.0%, and 2.8% greater (P ≤ 0.002), carcass WOG, breast, and tenderloin yields, while SG had 2.7%, 5.0%, 7.5%, and 1.2% greater (P < 0.0001) wings, leg quarters, frame, and skin yields, respectively. CONV breast 24-h pH and cooking loss were greater (P ≤ 0.04) than SG. While SG thigh shear force was greater than CONV (P = 0.008), breast shear force was the lowest for CONV stocked at 29 kg/m2 and the greatest for SG stocked at 37 kg/m2 (P = 0.04). SG had a paler breast than CONV, while CONV had a yellower breast than SG (P < 0.0001). While SG had a redder thigh than CONV (P = 0.002), SG stocked at 29 kg/m2 had a redder breast than SG stocked at 37 kg/m2, with both CONV groups intermediate (P = 0.04). These results indicate that differences in male broiler meat quality were affected more by strain than by stocking density. Compared with CONV, SG broiler meat quality was more affected by stocking density in this study.