PROTEIN AND AMINO ACID COMPOSITION OF MILK OF HOLSTEIN CROSSBREEDS OF DIFFERENT PROPORTION OF HOLSTEIN BREED BLOOD
To improve the domestic cattle breeds, North American Holsteins are widely used. The research goal is to study the protein and amino acid composition of milk of the crossbreeds of Red Steppe and Red-Pied Holstein breeds with a proportion of Holstein breed blood as much as 1/2; 3/4 and 7/8. The tests of the biochemical composition of milk of Red Steppe cattle and its crossbreds with different proportions of Holstein blood revealed that holsteinization contributes to significant increase of protein content by 0.09-0.011% in milk of crossbred first-calf heifers; a significant increase in the content of essential amino acids was found as following: milk from half-blooded cows - by 0.8 g L; 3/4 proportion - by 0.9 g L (P < 0.05) and 7/8 proportion - by 0.7 g L; in terms of the total content of non-essential amino acids - by 0.5 g L; 0.6 g L and 0.5 g L respectively. The protein composition of milk of the first-calf heifers of all studied crossbreeding variants in whole conformed to the GOST (Natl. Standard) and production requirements for raw materials for whole-milk products.