Analysis of comb morphology in Sichuan Mountaineous Black-bone chickens and its correlation with growth performance

Biological ornaments, such as the comb in chickens, act as condition-dependent indicators of mate quality and are influenced by genetic, hormonal, and environmental factors. In this study, we investigated the histomorphological development of combs in Sichuan Mountaineous Black-bone chickens and examined their relationship with growth performance and hormone levels. At market age, the chickens were classified into large- and small-comb groups based on comb size, and their skeletal traits, slaughter performance, and meat quality were evaluated. The results showed that male chickens with large combs exhibited significantly better skeletal development, including greater shank circumference, breast depth, and breast circumference, although slaughter traits relative to body weight did not differ significantly. In female chickens, a similar pattern was observed in the large-comb group, but the differences were not statistically significant. Meat quality analysis revealed that male chickens with large combs had higher pH and moisture in breast muscle, while crude protein and crude fat were higher in those with smalle combs. L* value and inosine monophosphate (IMP) were more abundant in the breast muscle of female chickens with large combs. Growth hormone (GH) levels were positively associated with comb traits in both sexes, whereas testosterone showed no significant correlation. Gene expression analysis indicated that BMP2 and HSD17B2 were upregulated in small-comb chickens, while chondroadherin-like (CHADL) was upregulated in large-comb chickens. These findings enhance our understanding of the biological basis of comb development and its link to growth performance, offering useful insights for improving productivity in poultry through ornamental trait selection and economic and scientific values.