Genetic Variants Of ESR And FSHβ Gene And Their Association With Reproduction Traits In Pigs

Because of its very low heritability in litter size of pig, the improvement of the litter size is limited by the conventional breeding technology. It is very important to find the major gene and the genetic marker related to the litter size. In this study, 323 pigs including Laiwu Black, Lulai Black, Licha Black, Luyan White, New Yimeng Black, Yorkshire, Landrace and Duroc were selected to detect genetic variants of ESR and FSHβgene by PCR-SSCP. According to the genotypic frequency of these two genes, we calculate the allelic frequency of every pig group.and the genetic effects of the genes on litter size were also analyzed by the least square analysis. Gathering the litter size data of examined pigs (including the total number of born and the number of born alive), we analyze the effects of them on prolificacy, including the effects of single gene and their combined genotypes. The main results are as follows:For ESR, frequencies of the allele A and B in gene ESR are different, so do the frequencies of its genotypes. Among alien variety tested, for the abroad pig, the frequency of allele A and the frequency of genotype AA are relatively high. While, the frequencies of allele B in Shandong local pig is higher than 0.6.The result of x2 test showed that ,except the LW pig ,all the other population fitted the H-W equilibrium situation(P>0.05).No matter in TBA and NBA, genotype BB is higher than AA and AB, while genotype AB is higher than the AA type. As a result for ESR the average TNB and NBA of BB was 1.38 and 1.15 more than AA in the first parity, while 0.96 and 0.91 more than AA in the later parities respectively , and the effect of the genotype on reproduction traits is significant (P<0.05).For FSHβ, frequencies of the allele A and B in gene FSHβare different, so do the frequencies of its genotypes. Among alien variety tested, for the abroad pig, the frequency of allele A and the frequency of genotype AA are relatively high. While, the frequencies of allele B in Shandong local pig is higher than 0.6.No matter in TBA and NBA, genotype BB is higher than AA and AB, while genotype AB is higher than the AA type. The result of x2 test showed that all the other population fitted the H-W equilibrium situation(P>0.05),except the LW ,LL and LC pig. In the first parity, the effects of every genotype in FSHβis successively BB, AA, AB, from high to low, the average TNB and NBA of BB was 1.23 and 1.36 more than AA .While in the later parities, BB was 0.74 and 0.82 more than AA, and the effect of the genotype on reproduction traits is significant (P<0.05).Results showed that for the combined genotype BBBB the TNB and NBA of BBBB was 2.54 and2.65 more than AAAA in the first parity, while 2.29 and 2.35 more than AA in the later parities respectively at the same time (P<0.05). The effects of combined genotypes of ESR and FSHβhave no obvious law .Its genetic effects on prolificacy are not simply the multiplications of every genotype. But its effect of combined genotypes is higher than the effect of individual genotype. It offers the basis for its application in production.Age is one important factor influencing of prolificacy, the TNB of first born is less than the TNB of the still-born, so does in the NBA.In this research the effects of ESR and FSHβon prolificacy is proved to be obvious, and they are abundant in polymorphism. From these results we can putatively drew the conclusion that these two genes could be used to select the pig for high reproduction trait in molecular marker assisted selection programs, in order to improve the level of prolificacy.