Relationship of genotypes of csn3 gene in milk production and proportions of its components in Holstein Friesian cows bred in Iraq

Abstract

The study was conducted on 50 Holstein cows bred in Iraq at the Taj Al-Nahrain cow station in Al-Qadisiyah Governorate, of different ages and weights. The process of analyzing the milk components was carried out in the laboratories of the Animal Production Department in the College of Agriculture, Al-Muthanna University. The process of extracting the DNA and examining its purity inside the molecular genetics laboratory in the College of Agriculture University of Basra, and the period of conducting the study was from the beginning of drawing milk and blood samples from 02.12.2021 to 02.03.2022, followed by extraction of the DNA and sending it to China, in order to find out the genotypes of the milk protein gene CSN3 and its relationship to the productive characteristics of milk and its composition, when amplifying a piece. Two haplotypes were obtained from the CSN3 gene. The first pattern differs from the second by the shift of the nitrogenous base from C to T at sequence 69 and the change of the amino acid from ALA to threonine (THR). Isoleucine (ILE) to aspartate ASP, as two genetic mutations were detected that led to a change in the type of amino acid, and the number of cows that represented the first type was 30, and the second haplotype was 20. It was found that the patterns of the CSN3 gene had a highly significant effect (P≤0.01), as the second individual pattern, was superior to the first pattern in daily, weekly and monthly milk production and the production of the first stage of milk. The first is for the CSN3 gene on the second haplotype in protein and lipid ratios.