Analysis of PRLR and BF Genotypes Associated with Litter Size in Beijing Black Pig Population

This study is aimed at using the DNA mutations in the prolactin receptor (PRLR) and properdin (BF) genes to determine associations between the genotype and litter size in the Beijing Black pig population. A total of 321 Beijing Black pig sows were genotyped using the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method, with the Alu I and Sma I for PRLR and BF genes, respectively. Two different alleles of PRLR and BF genes were identified: allele A (0.25) and B (0.75) of the PRLR gene, allele A (0.13) and B (0.86) of the BF gene. The association analysis between the genotypes and the litter size were estimated with the method of the general linear model. The analysis results of PRLR showed that in first parity, sows with genotype AA had a larger litter size than sows with genotype AB and BB, but the difference was statistically not significant. In later parities, statistically significant (P < 0.05) differences were seen between sows with genotypes AA and AB, and BB of the PRLR gene. The associated analysis results between genotypes and litter size (total number born, TNB, and number born alive, NBA) showed that there were no significant differences in the first parity sows with different genotypes of the BF gene, but significant differences appeared in NBA between the sows of genotypes AB and BB, in later parity, for which significantly higher values were observed in the offspring of heterozygotes. Considering the consistent genotypic effect on the litter size of both sows in first parity and later parity, it was concluded that the locus of the PRLR gene, digested with Alu I, could be the gene maker for the litter size in Beijing Black pigs.