The relation of GH1, GHR and DGAT1 polymorphisms with estimated breeding values for milk production traits of German Holstein sires

We analysed the relations of estimated breeding values (EBV) of 315 German Holstein sires to their genotypes in growth hormone gene (GH1), growth hormone receptor gene (GHR) and acylCoA-diacylglycerol acyltransferase 1 (DGAT1). The strong relation of DGAT1 K232A to the estimated breeding values for milk production traits has been confirmed, when allele DGAT1(K) was connected with higher milk fat yield, milk fat and milk protein content, while allele DGAT1(A) increased milk yield and milk protein yield. The effect of DGAT1 genotype explained from 4.70% of variability of EBVs for fat yield to 31.90% of variability of EBVs for fat content. The evaluation of GH1 127 Leu/Val and GHR 257 SNP polymorphisms did not reveal an association of their polymorphism with EBVs for milk production traits, except the EBVs of GHR(G)/GHR(G) homozygotes for fat yield, which were significantly lower. The effect of GH1 or GHR genotype explained only a negligible portion of variability of EBVs (R-2 < 1.00% in most cases).