Heritabilities of Relative Percentages of Major Bovine Casein and Serum Proteins in Test-Day Milk Samples

Individual milk samples were obtained from Holstein cows in 62 herds in Quebec from November 1979 to November 1981. Milk samples were analyzed for somatic cell count and relative percentages of as-, /3-, and ~:-caseins, /3-1actoglobulin, a-lactalbumin bovine serum albumin, and immunoglobulins. The model used to analyze the data included herd, month of test, age of cow, and somatic cell count as fixed effects and sire, cow within sire, and error as random effects. Restricted maximum likelihood procedures were used to fit the model to the data. Heritabilities obtained for relative percentages of as-, ~, and g-caseins were .02, .03, and .005. Heritabilities obtained for relative percentages of ~-lactoglobulin, 0t-lactalbumin, bovine serum albumin, and immunoglobulins were .24, .14, .15, and .02.