Effects of single-nucleotide polymorphisms in insulin-like growth factor-1 and insulin-like growth factor-2 genes on growth performance of centrally tested Duroc boars using segregated early weaning entrance

Insulin-like growth factor (IGF)1 and IGF2 genes were reported to be associated with growth performance in pigs. This study investigated the effects of a single-nucleotide polymorphism (SNP) in IGF1 (IGF1-G201C) and two SNPs in IGF2 intron 8 (IGF2-in8-C27222G and IGF2―in8-C27322G) on the growth performance of centrally tested Duroc boars in Taiwan. In total, 735 Duroc boars were subjected to performance testing using segregated early weaning entrance. The IGF1-G201C, IGF2-in8-C27222G, and IGF2-in8-C27322G genotypes were determined by a polymerase chain reaction-based restriction fragment length polymorphism analysis. The performance traits included the average daily gain, feed conversion ratio, back-fat thickness, and age at 110 kg of body weight. The statistical model included the test season, and the IGF1-G201C and IGF2-in8-C27322G genotypes, with the starting age used as a covariate. The genotypic frequencies of the CC, CG, and GG genotypes in IGF1-G201C were 0.4%, 13.7%, and 85.9%, and of the CC, CG, and GG genotypes in the IGF2-in8-C27322G locus were 12.0%, 42.3%, and 45.7%, respectively. No polymorphism was found in the IGF2-in8-C27222G locus. The SNP of IGF1-G201C showed no significant effect on growth performance. However, the IGF2-in8-C27322G genotype significantly influenced the average daily gain, feed conversion ratio, and age at 110 kg of body weight. The results suggest that the SNP in the IGF2-in8-C27322G locus can be used as a candidate marker gene for improving the growth performance of Duroc boars under a segregated early-weaning entrance test system.