Polymorphism of Insulin-like Growth Factor-I Gene in 13 Pig Breeds and its Relationship with Pig Growth and Carcass Traits

The polymorphism of insulin-like growth factor-I (IGF-I) in 13 pig breeds (total n=559) was detected by PCR-Hha I- RFLP, and allele A (151 bp and 28 bp) or allele B (116 bp, 35 bp and 28 bp) were observed. In these pig breeds, it was found that European pig breeds carried high frequencies of allele B, while Chinese native pig breeds carried high frequencies of allele A. Meanwhile the role of porcine IGF-I was investigated in 117 Nanchang White pigs and 360 Large Yorkshire pigs. Eight traits about growth and carcass were recorded for analyzing the associations between IGF-I gene polymorphism and performance quantitative traits. In the Nanchang White pigs, those with AA genotype generally had higher birth weight than those with AB genotype (p<0.05), but all these genotypes had no significant effect on the other traits which had been analyzed. In Large Yorkshire pigs, those with BB genotype had higher 2 months and 6 months body weight than those with AA genotype (p<0.05), and had a thicker hind-back-fat thickness and mid-back-thickness than those with AB and BB genotypes (p<0.05). And those with BB genotype were the thinnest in Large Yorkshire. Furthermore, pigs with AA genotype had a lower lean percentage than those with AB and BB genotypes (p<0.01), and the lean percentage of those with BB genotype was the highest. Based on these results, it is possible to make the IGF-I gene locus into the application of marker-assisted selection programmes.