Effects of Milk Protein Polymorphisms on Milk

A Total of 2005 first lactation Holstein-Friesian cows with known 305-d lactation yield for milk, fat, and protein were available. For each cow, genotypes for s1-casein, ß-casein, -casein, and ß-lactoglobulin were known. It appears that the milk protein variants s1-casein, ß-casein, and -casein may not be segregating independently. Effects of genetic variants of milk proteins on estimated individual Parmesan cheese yields were investigated. The relationships of the genetic variants of milk proteins to total lactation milk yield, fat yield, protein yield, fat percentage, and protein percentage were also investigated. Least squares analysis of the data indicated that s1-casein genotype
significantly influenced milk yield, fat yield, and protein yield with the highest yields obtained for the genotype BB. Cheese yield on a fixed amount of milk and fat percentage were significantly related to ß-lactoglobulin genotype with the highest estimates obtained for BB. Protein percentage was influenced by s1-casein and -casein, with the genotypes BC and BB, respectively, having the highest percentages. Significantly higher lactation
cheese yields were estimated with s1-casein genotype BB. Using the prediction equation to estimate cheese yield (on data from another study), it was found that differences in Parmesan cheese yield from milk of either -casein genotype AA or BB were greater than expected based on composition. Differences in salted curd yield from another study using milk of either ß-lactoglobulin genotype AA or BB were also greater than expected.