Factors affecting growth performance, carcass quality and the occurrence of white striping and wooden breasts in broilers

The present study aimed at evaluating whether growth performance, carcass and meat quality in broiler chickens, and the occurrence of white striping and wooden breast abnormalities could be affected by genotype (S=standard vs. H=high breast yield commercial crossbred), sex, and feeding regime (ad libitum vs. restricted rate, i.e. 80% of ad libitum from 13 to 21 d of age). To this aim, 768 one-day-old chicks were housed in 32 pens (24 birds/pen of 2 m2) and slaughtered at 46 d of age in a commercial slaughterhouse. The S broilers showed higher final live weight (3,270 vs. 3,139 kg; P<0.001) and lower feed conversion (1.56 vs. 1.61; P<0.001) compared to the H genotype. Breast yield did not vary between strains, whereas the S broilers exhibited higher thigh yield (18.3 vs. 17.7%; P<0.01) and pHu (5.89 vs. 5.85; P<0.05), lower lightness (L*, 45.3 vs. 46.2; P<0.05), and higher thawing losses (10.7 vs. 9.6%; P<0.05) of the P. major muscle compared to the H genotype. Males showed higher (P<0.001) final live weight (3,492 vs. 2,845 kg), daily weight gain (77.3 vs. 62.8 g/d) and feed intake (119 vs. 102 g/d), and lower feed conversion (1.54 vs. 1.63) compared to females, besides heavier carcasses, higher dressing percentage and hind leg yield at slaughter. Besides, the breast had higher pHu (5.89 vs. 5.85; P<0.01) and was less yellow (b*, 13.4 vs. 14.2; P<0.05) in males than females. Feed restriction impaired final live weight (3,142 vs. 3,194 kg; P<0.01), despite compensatory growth (95.4 vs. 91.5 g/d; P<0.001) was measured during the second period (22 to 46 d) in the previously restricted chickens compared to those always fed ad libitum, and improved feed conversion (1.57 vs. 1.60; P<0.01). At slaughter, the restricted broilers showed lower carcass weight, dressing percentage (73.5 vs. 73.9%; P<0.05), breast yield (39.5 vs. 40.6%; P<0.10), and higher thigh yield (18.3 vs. 17.7%; P<0.05) compared to the birds always fed ad libitum, besides higher breast pHu (5.89 vs. 5.85; P<0.01); otherwise the restricted birds tended to have a higher proportion of white-striped breasts compared to the birds fed ad libitum (79.5 vs. 69.5%; P<0.10). Wooden breast occurrence averaged 12.2% and was significantly lower in females than in males (8.0 vs. 16.3%; P