Polymorphism in SNP G1 of the GDF9 gene associated with reproductive traits in Bulgarian dairy sheep

Abstract

The Bulgarian Dairy Synthetic Population (BDSP) is the most numerous sheep breed in the country with a fertility of about 150%. Fertility in sheep is mainly determined by several major genes known as fecundity genes (Fec), one of which is GDF9 (growth differentiating factor 9). The aim of this study was to analyze the association of the GDF9 gene polymorphism at SNP G1 with litter size depending on age and birth type in BDSP ewes. The analysis included 163 sheep in which a 462 bp fragment of exon 1 of the GDF9 gene was amplified and subsequently cut with the restriction enzyme HhaI. As a result, two alleles were established: the wild-type G (with a frequency of 0.76) and the mutant A (with a frequency of 0.24), as well as the three possible genotypes AA, AG and GG with frequencies of 0.06, 0.35 and 0.59, respectively. There was no statistically significant difference in litter size between different genotypes at SNP G1. Significant differences were found in the litter size of the 2nd lambing (1.52) compared to the 4th lambing ewes (1.77), and in the single-born ewes (1.56) compared to ewes born as twins (1.70) (p ≤ 0.05). Proven higher fertility was observed in ewes born as twins with genotype AA (1.97) compared to twins born as carriers of heterozygous genotype AG (1.65) (p ≤ 0.05).