Several polymorphisms in different gene loci have been noted to affect production traits such as milk yield and milk composition. The present study aimed to determine the allelic and genotypic frequency of the DGAT1 gene and evaluate the associations between DGAT1 genetic variants and milk yield and its chemical composition of local Iraqi cattle. Blood samples from 100 cows were obtained for DNA isolation. The primer used in this study amplified 411-bp fragments at exon 8 of the DGAT1 gene. DNA sequencing methods were applied to detect single nucleotide polymorphism of the DGAT1 gene in 100 cows. The nucleotide sequences of exon 8 of the DGAT1 gene were registered for local Iraqi cattle in the National Center for Biotechnology Information (NCBI), DNA Data Bank of Japan (DDBJ), and the European Nucleotide Archive (ENA) under the following accession numbers (LC492073 and LC492074). The results showed the presence of two polymorphic sites leading to the construction of 2 different haplotypes in the cow. Haplotype diversity was 0.536, while nucleotide diversity was 0.0031. Two single-nucleotide polymorphism (SNP) loci of the DGAT1 gene were detected, namely A10433G (A/G) and A10434C (A/C). The resulting of this mutation changes lysine to alanine substitution at position 232 (A232K mutation) of amino acid sequence. Geneious software V. 2020.0.4 was used to detect genotypes of the DGAT1 gene, as the sequence alignment showed the presence of three genotypes. The genotypic frequencies of KK, KA, and AA were 0.40, 0.30, and 0.30, respectively. Frequencies of K and A alleles were 0.60 and 0.40, respectively. The KK genotype was significantly (P 0.05) associated with higher fat yield. Therefore, the DGAT1 gene could serve as a genetic marker for the selection of fat yield in cows.
The Prediction of the Expected Current Selection Coefficient of Single Nucleotide Polymorphism Associated with Holstein Milk Yield, Fat and Protein Contents