THE INFLUENCE OF GENETIC-VARIANTS OF MILK-PROTEINS ON THE COMPOSITIONAL AND TECHNOLOGICAL PROPERTIES OF MILK .3. CONTENT OF PROTEIN, CASEIN, WHEY-PROTEIN, AND CASEIN NUMBER

Milk samples of 801 individual cows of different genetic variants were analyzed for the content of protein, casein and whey protein; the cas ein number was calculated. Milk with the genotype alpha(s1)-Cn BC had significantly higher levels of protein and casein than milk with alpha (s1)-Cn BB, whereas alpha(s1)-Cn CC-milk showed the lowest concentrati on of protein and casein. Concerning the genotypes of the beta-Cn locu s, the highest levels of protein and casein were found for beta-Cn A(2 )C and the lowest levels were associated with the genotypes BB and A(2 )A(2); the differences between the genotypes were significant. The 7 k appa-Cn genotypes (AA, AB, AC, AE, BB, BC, and BE) investigated did no t show significant effects on the protein and casein values. Out of th e 7 beta-Lg genotypes tested (AA, AB, AD, BB, BC, BD, and BW), the gen otype BC was associated with the highest protein content and the genot ypes BC and BE had the highest concentration of casein; differences in the protein and casein content between the beta-Lg genotypes were in some cases significant and in some cases not. The whey protein content was solely influenced by the genetic variants of the beta-Lg locus an d thus milk with the genotypes beta-Lg AA and AD had the highest amoun t of whey protein. The genetic variants of the beta-Lg locus also infl uenced the casein number significantly. The casein number increased in the order: beta-Lg AA (75.68%), AD, AB, BW, BD, BB, and BC (78.97%). The differences between the genotypes beta-Lg BC, BE, BD and AB, AD, a nd AA, respectively, were significant. The casein number of milk with the genotype beta-Lg, BW (77.80%) was significantly different from tha t of the genotype beta-Lg AD (76.26%) and beta-Lg AA (75.68%).