Polymorphism of insulin-like growth factor I gene in six chicken breeds and its relationship with growth traits

The polymorphism of insulin-like growth factor I (IGF I) in 6 chicken breeds (total n=515) was detected by PCR-Pst I-RFLP, and allele A (621 bp) or allele B (364 and 257 bp) were observed. In these chicken breeds, it was found that exotic chicken carried high frequencies of allele B, while Chinese native chicken breeds carried high frequencies of allele A. Meanwhile the role of IGF I was investigated in 133 Ningdu Yellow chicken and 162 Wanzhai Yellow chicken. Five growth traits were recorded for analyzing the association between IGFI gene polymorphism and performance. In both the Ningdu and Wanzhai Yellow breeds, body weight at 4 months was significantly higher with BB genotype than with AA genotype (p<0.05). Furthermore, body weight at 2 months in the Wanzhai Yellow breeds was also higher with BB genotype than with AA genotype (p<0.05). There were no differences among the genotypes for the other traits studied. Based on these results, it is necessary to do more studies on IGFI before making the IGFI locus into the application of maker-assisted selection programms.