MILK OF BLACK-WHITE COWS WITH DIFFERENT GENES OF CAPPA CASEIN AND DIACYLGLYCEROL OF O-ACYLTRANSFERASE FOR CHEESEMAKING

Abstract

The purpose of the research is improving the quality and technological properties of milk from black-and-white cows. The research was conducted on first-calf cows of a black-and-white breed in LLC «Dusym» of the Atninsky district of the Republic of Tatarstan. Three groups of experimental cows were formed depending on the genotype of CSN3 and DGAT1, which have equal lactation month. Cheese making milk obtained from cows with different allelic variants of the kappa-casein and diacylglycerol O-acyltransferase genes was studied. DNA testing was performed on the CSN3 and DGAT1 genes of experimental cows and allelic variants of these genes were determined by pol-ymerase chain reaction followed by analysis of restriction-site polymorphism. It was found that milk of cows with the genotype CSN3 AB and CSN3 BB, when exposed to rennet, showed a better yield of a dense casein clot (80 and 100%) and separation of serum (P <0.05), with a shorter coagulation time (20.3 and 16.5 min; P <0.05-0.01). Ac-cording to the DGAT1 gene, first-calf milk with the allelic variant DGAT1 AK and DGAT1 KK had the advantage, respectively, 86.7% and 85.7%, 24.0 and 25.7 minutes. The worst milk coagulation time is typical for CSN3 AA group – 29.5 minutes and DGAT1 AA one – 30.4 min. In terms of milk coagulation time, type II (15-40 min.) groups have the genotype CSN3 AB and CSN3 BB with the largest share of cows in the herd – 80.0 and 71.4% and with the genotype DGAT1 AK and DGAT1 KK – 86.6 and 85.7%, respectively. Thus, milk obtained from cows with the kappa-casein gene allele B and the diacylglycerol O-acyltransferase gene allele K gene in the genotype has the best cheese-making properties.