Genomic Variants Associated With Oocyte and Embryo Production in Dairy Gir Cattle

Abstract

The use of in vitro fertilization protocols associated with genomic selection increases genetic gain in dairy cattle. The aims of this study were to uncover genetic variants in a specific interval on BTA7 and to investigate their effects on the number of oocytes and embryos in dairy Gir. Previous research uncovered a region on chromosome 7 (BTA7) associated with oocyte and embryo production. In the current study, genomic variants were investigated in this region for 12 sires with positive Predicted Transmission Ability for milk production, which are widely used in dairy herds to produce daughters for oocyte and embryo production. Several variants were identified and four variants were classified as lead SNPs. ANOVA was carried out for the daughters' genomic estimated breeding value (GEBV) and phenotypes according to the genotype of the bulls. Two lead SNPs were single-nucleotide substitutions and both resulted in premature stop codons in XRCC4 and HAPLN1 genes. A deletion of five thymines in an intergenic region occurred in the third lead SNP. The fourth lead SNP involves the deletion of one nucleotide in the EDIL3 gene, causing a frameshift. All genotype groups were significantly different for GEBV and some for phenotype. In conclusion, the mutant alleles of each lead SNP were associated with the production of oocytes and embryos in the dairy Gir, leading to a decrease (rs518509552, rs438544900), an increase (rs450555472) when homozygous or a decrease (rs470818992) when heterozygous. Research is underway to investigate the association of such variants with dairy production and environmental resilience traits.