Identification of TAC3R gene SNP site in Kele pigs and their effects on reproductive traits

【Objective】This study aimed to explore the correlation between the single nucleotide polymorphism（SNP） sites of the tachykinin receptor 3 gene（TAC3R） and the reproductive performance of Kele pigs, and to screen out genetic markers related to reproductive traits, so as to provide technical support for accelerating breed improvement of Kele pigs. 【Method】A total of 195 healthy multiparous Kele pigs with more than 2 litters were selected as the research subjects. The Sanger direct sequencing was employed to identify SNP sites of the TAC3R gene, and the population genetic parameters of each SNP site were calculated by SHEsisPlus. Subsequently, the genetic effects of SNP site genotypes or haplotypes on 5 reproductive traits of Kele pigs were analyzed using the general linear model（GLM） in SPSS 22.0. 【Result】Five SNPs sites were detected in the TAC3R gene of Kele pigs: g.117686266 T＞C, g.117686381 A＞G, g.117686384A＞G, g.117688503 T＞C, and g.117688518 T＞C. Among these sites, g.117686381 A＞G and g.117686384 A＞G showed complete linkage, while g.117688503T＞C showed no linkage with the g.117686266T＞C, g.117686381A＞G, and g.117686384A＞G. However, strong linkage disequilibrium was observed among the other SNP sites. A total of 5 haplotypes and 10 diplotypes were detected in the 5 SNPs sites. Among the haplotypes, the frequency of H5 was the highest（0.433）, the frequency of H2 was the lowest（0.059）. For diplotypes, H3H5 had the highest frequency（0.221） and H1H4 had the lowest frequency（0.031）. All the 5 SNPs sites exhibited moderate polymorphism（0.25＜PIC＜0.50） in the Kele pig population, and their genotypic distributions did not deviate from Hardy-Weinberg equilibrium (χ²_-HWE＜5.991).The g.117688503T＞C site significantly influenced the average litter size and weaned piglet number, with the TT genotype exhibiting significantly higher values for both traits compared to CC genotype. The g.117688518T＞C site significantly influenced weaned piglet number, with CC genotype individuals showing significantly higher numbers than TT genotype individuals. The correlation analysis of the SNP site diplotypes of TAC3R gene and reproductive traits in Kele pigs revealed that the H2H4 type was the optimal for average litter size, average live litter size, and weaned piglet number, while the H1H3 type was the optimal for average weaning weight. 【Conclusion】Five SNPs sites are detected on the TAC3R gene of Kele pigs, among which the g.117688503 T＞C and g.117688518 T＞C sites have significant effects on the reproductive performance of Kele pigs. TAC3R gene can be considered a candidate gene for reproductive traits of Kele pigs, and the haplotype H2H4 can serve as a reference for molecular marker-assisted selection.