Associations between GHR and IGF-1 Gene Polymorphisms, and Reproductive Traits in Wenchang Chickens*

Alleles of physiological candidate genes for reproductive traits, insulin-like growth factor-1 (IGF-1), and growth hormone receptor (GHR) were assessed to determine their associations with total egg production (NE), average days of continual egg-laying (ADCE), and number of double yolk eggs (DYE) in Wenchang chickens (Chinese indigenous breed). PCR-RFLP was used for genotype identification. The frequency of restriction enzyme C1/C2 alleles in the population was 0.53 (C1) and 0.47 (C2) for IGF-1. For GHRintron 2 it was 0.06 and 0.94 for (A1) and (A2), respectively, while for GHR-intron 5 it was 0.20 (B1) and 0.80 (B2). Four significant associations were found (P < 0.05): between IGF-1 polymorphism, and NE (300 d), NE (400 d), and ADCE, and between GHR polymorphism and DYE. Two significant effects were observed: for IGF-1 and NE (300 d), and for GHR intron 2 and DYE. The current research supports the effects of GHR and IGF-1 genes on the reproductive traits of chickens.