Association with TGF-β1 gene polymorphisms and reproductive performance of Large white pig

As a multifunctional cytokine, transforming growth factor-beta1 (TGF-β1) was detected in the utero-placental interface during early pregnancy in the pig and believed to enhance trophoblast attachment to the endometrium. In this experiment, we selected TGF-β1 as the candidate gene affecting litter size in pigs. Four polymorphic loci of TGF-β1 gene were found by PCR-SSCP (single-strand conformation polymorphism) in Large white sows (n = 567): C→T mutation at 33nt in the intron 4; G→A mutation at 179nt in the intron 6; C→T mutation at 1043nt in the intron 6; GG→AA linkage mutations at 2490nt and 2494nt respectively. We haplotyped these SNPs as: CGCAA (denote as P) and TATGG (denote as K). The effects of three haplotypic combinations (HCs) of PP, PK and KK on litter sizes were investigated by a linear model. It was found that for the first parity litters, the least squares mean for total number born (TNB) of KK was 1.02 piglets/litter, higher than that of PK (p < 0.05), 0.49 piglets/litter higher than that of PP (p > 0.1). There were no significant differences between HCs on the second parity. The result indicated that KK HCs was significantly associated with pig litter size.