Phenotypic characteristics of upright and pendulous comb among chicken breeds and association with growth rate and egg production.

Upright and pendulous combs commonly exist in most single-comb chicken breeds. Here, the phenotypic characteristics of upright and pendulous combs in chickens and association with growth rate and egg production were analyzed. Phenotypic frequencies of upright and pendulous comb were investigated in five chicken breeds; the phenotypic frequencies of complete pendulous comb (CPC) and partial pendulous comb (PPC) ranged from 10.1% to 29.0% and 21.8% to 65.3%, respectively. CPC hens produced more eggs than PPC hens (P < 0.05) in Nongda-3, Huainan and Wenchang breeds. In Huainan breed, CPC males were heavier than PPC males at 12 and 16weeks of age, while CPC females were heavier at 24weeks of age. PPC and CPC chickens have greater (P < 0.05) comb length, comb height and comb index than upright comb (UC) chickens. There was no significant difference in comb phenotypic frequency distribution between the offspring from UC(male) x CPC(female) and CPC(male) x UC(female); however, it differed (x(2) = 45.12, P < 0.01) between offspring from UC(male) x UC(female) and CPC(male) x CPC(female). These results suggested that the comb phenotype does not appear to be Z-linked; the effective loci influencing the trait could be estimated in a further study.