Effect of Single Nucleotide Polymorphisms in IGFBP2 and IGFBP3 Genes on Litter Size Traits in Berkshire Pigs

Litter size is among the most important traits in swine breeding. However, information on the genetics of litter size in pigs is lacking. In this study, we identified single nucleotide polymorphisms (SNPs) in the insulin-like growth factor binding protein 2 and 3 (IGFBP2 and IGFBP3) genes in Berkshire pigs and analyzed their association with litter size traits. The IGFBP2 SNP was located on chromosome 15 intron 2 (455, A T) and the IGFBP3 SNP was on chromosome 18 intron 2 (53, A G). The AT type of IGFBP2 and the GG type of IGFBP3 had the highest values for all litter size traits including total number born (TNB), number of pigs born alive, and breeding value according to TNB. Homozygous GG pigs expressed higher levels of IGFBP3 mRNA in the endometrium than pigs of other genotypes, and a positive correlation was observed between litter size traits and IGFBP3 but not IGFBP2 expression level. These results suggest that SNPs in the IGFBP2 and the IGFBP3 gene are useful biomarkers for increasing the reproductive productivity of Berkshire pigs.