Comparative analysis of milk amino acid composition and protein biological value in purebred cows and their crossbreds

Abstract

The milk protein biological value of crossbred cows has been compared with purebred lines. The research has been carried out on Ukrainian Black and White dairy cows and crossbred lines of the first generation obtained due to crossbreeding with Brown Swiss breed. The same has been done on Ukrainian Red and White dairy cows, Montbéliarde breed and crossbred lines of the first-generation, obtained due to crossbreeding with Ukrainian Red and White dairy cows. It has been established that the milk protein of crossbred cows has more balanced composition of (MPC) and more appropriate ratio for processing. The essential amino acid milk analysis of the investigated breeds has found that there is a big amount of leucine (9,22–9,87 g/100 g protein of milk), phenylalanine + tyrosine (9.04–9.75 g/100 g of milk protein) and lysine (5.81– 6.73 g/100 g protein of milk). Also, there is a minimum amount of methionine + cystine – (3.32–3, 88 g/100 g protein of milk). The first limitaive amino acid in the milk protein of Ukrainian Black and White breed is valine, the content of which is 97.2 % of the total amount in the scale of the reference protein. The second limitaive amino acids are methionine + cystine, the content of which is 94.8 %. The amino acids haven’t been found in the milk protein of crossbred cows. It means that the composition of each (MPC) is appropriate for human needs in the reference protein. The milk protein biological value of crossbred cows is somewhat higher than in purebred animals. The milk protein of the investigated breeds does not contain amino acids, the correlation of which is less than optimal in comparison with the amino acid formula of human needs. The milk of Red and White dairy cows and Montbéliarde breed has best protein quality. Key words: cow's milk, breed, amino acid composition, amino gram, biological value of proteins.