PROTEIN COMPOSITION AND NUTRITIONAL MILK VALUE OF COWS OF UKRAINIAN BLACK-AND-WHITE DAIRY BREED WITH DIFFERENT GENOTYPES OF CAPA-CASEIN (CSN3)

Abstract

The article presents the results of studies of protein composition and nutritional milk value of Ukrainian Black-and-White dairy cows with different genotypes of kappa-casein. It was found that the milk of cows with the BB genotype contained more total protein by 0.41 and 0.28 %, the mass fraction of protein (Pro Total) – by 0.37 and 0.25 %, with a probable advantage over the protein content (casein) – by 0.46 and 0.29 % (p≤0.001) and the total amount of casein and globulin – by 0.39 and 0.27 % (p≤0.001) against analogs with genotypes AA and AB. There are differences in the chemical composition and physicochemical properties of milk. In particular, the difference in mass fractions of lactose and dry matter in milk between cows with the genotype BB and AA and AB was respectively 0.16 % (p≤0.001) and 0.11 % (p≤0.01) and 0.64 % (p≤0.001) and 0.37 % (p≤0.01). No less valuable in terms of mass fraction of dry matter was the milk of cows with genotype AB, in which the growth of this indicator against animals with genotype AA was at the level of 0.28 % with a statistically significant difference between them (p≤0.01). Freezing point and density as marker criteria that characterizing the presence of falsification were practically unchanged and did not exceed the permissible norms and amounted to 0.551–0.553 °С and 1028.04–1028.45 kg/m3. The content of somatic cells in the milk of cows of different genotypes of kappa-casein was within the permissible level according to the state standard, which indicates the absence of mastitis. Cows with genotype AA had an increased level of titrated acidity and concentration of free hydrogen ions (p≤0.01 – p≤0.001) against analogs with genotypes AB and BB. However, in general, the hydrogen pH of the milk of cows of all groups had a weakly acidic environment, the values of which ranged from 6.66 units. pH in cows with genotype BB up to 6.71 units. pH – in animals with genotype AA.