Der Effekt von DGAT1-Genvarianten in Deutschen Holstein-Kuhen unter Produktionsbedingungen

The DGAT1 gene encodes the key enzyme for the final step in the synthesis of triglycerides. As such, it has an impact on milk yield and composition. The objective of this study was to investigate the genotype, allele, and haplotype frequencies of the K232A mutation and the VNTR promoter polymorphisms in the DGAT1 gene and to analyse the association of these DNA variants with milk production traits in a German Holstein population with 1380 cows. The observed allele frequencies are consistent with results from other Holstein populations. In correspondence with other studies the results of the present study confirm significant effects of the K232A mutation. The lysine variant resulted in reduced milk yield, increased fat and protein percentage as well as increased fat content. The VNTR alleles showed no significant effect. The most frequent VNTR allele 3 showed tendencies to an increased fat percentage and content, whereas the VNTR allele 5 had an opposite influence. Significant differences were observed between different maternal and different paternal haplotypes considering milk yield, fat, and protein percentage. The differences were stronger between the paternal haplotypes than between the maternal haplotypes. Furthermore, differences between maternally and paternally derived haplotypes might indicate parent-of-origin specific haplotype effects.The obtained results show that strong allele effects, for instance for the K232A locus, can also be detected under production conditions and that the genetic variability found on the female side is an additional resource for selection.