LAUSR

The aim of this study was to investigate β-Lactoglobulin, k-casein and DGAT1 gene polymorphism and to associate this polymorphism with milk composition and performance traits in Holstein cattle using the PCR-DNA sequencing approach. On the basis of farm records, accurate phenotypic data for milk composition and performance traits were obtained for seventy Holstein dairy cows. Blood samples were collected from each animal into tubes containing disodium EDTA as an anticoagulant for DNA extraction. PCR was carried out for amplification of fragments of exon 4 (301-bp) of β-Lactoglobulin, exon 4 (373-bp) of k-casein, and exon 7 (321-bp) of DGAT1 genes. DNA sequencing assessment elaborated single nucleotide polymorphisms (SNPs) in the investigated genes amongst the enrolled dairy cows. On the basis of the dairy cows that harbored identified SNPs in each gene, the animals were allocated into different groups. The least square means of the groups revealed a significant association (P ≤ 0.05) between SNPs and milk production and performance traits. Logistic regression model confirmed a highly significant effect of the identified SNPs on the studied traits, where a moderate to strong relationship was detected between the predictor (SNPs) and the grouping variable (Milk composition and performance traits). Consequently, the identified SNPs in β-Lactoglobulin, k-casein and DGAT1 genes could be used as candidates for developing marker assisted selection (MAS) for milk composition and performance traits in Holstein dairy cattle.