Associations Between Gh, Prl, Stat5a, Opn, Pit-1, Lep and Fgf2 Polymorphisms and Fertility in Holstein-Friesian Heifers

Abstract

In this study, it was aimed to investigate polymorphisms in seven genes (GH, PRL, STAT5A, OPN, PIT-1, LEP and FGF2) related to reproductive traits in dairy heifers. Frequency distributions of the genotypes between fertile and repeat breeder heifers groups were investigated. Allele effects on fertility were also analyzed. Blood samples were taken from a total of 160 Holstein-Friesian heifers and they were divided into two groups according to their artificial insemination numbers (AI). The heifers becoming pregnant after the first AI were used as the fertile heifers (FH, n= 80) and the heifers with 3 or more equal AIs were accepted as the repeat breeder heifers (RBH, n= 80). All the animals were genotyped by the PCR-RFLP method for seven genes and the association works were performed for 145 animals (RBH, n= 79; FH n= 66). For all loci investigated, two alleles and three genotypes were found for overall population with the exception that PRL locus had two alleles and two genotypes. The chi-square test (.2) revealed that the whole population and the two groups separately were at Hardy-Weinberg equilibrium. The genotype distributions of PIT-1 and STAT5A conspicuously differed between the FH and the RBH groups; however, these differences were not found significant. Association of GH-AB genotype was found significant on AI number for the first pregnancy. Mixed effect logistic regression model was used to investigate the allele effects on fertility. No linkage disequilibrium was detected between the investigated loci.