Genetic parameters for days open, milk yield, and fat and protein content of Swiss Braunvieh cows

Abstract

Genetic parameters for days open, milk yield and composition were estimated for the first lactation of 196 891 Swiss Braunvieh cows. These cows were daughters of four sets of sires: 1869 young purebred Swiss Braunvieh sires, 392 young 50% and 72 young 75% American Brown Swiss sires (crossbred) and all 3037 sires in the data, including proven sires. The linear model included fixed effects of herd production level-region-year-season group (herds were grouped within region because of small sizes) and sire group, and random effects of sire and error. Variance components for sire effects were estimated by Henderson's Method 4. Variance components for error were obtained as within smallest subclass mean squares. Heritability estimates were between 0.28 and 0.39 for milk yield, between 0.45 and 0.71 for percentage fat, between 0.39 and 0.80 for percentage protein and between 0.04 and 0.14 for days open. Estimates from crossbred sire data were slightly larger for milk yield, substantially smaller for percentage protein and slightly smaller for days open compared to estimates from purebred Swiss Braunvieh sire data. Genetic correlations between milk yield and composition traits were all negative and had larger absolute values for crossbred sire data. The genetic correlation between milk yield and days open was positive (i.e. antagonistic) and distinctly larger for data from purebred Braunvieh sires (0.45) than from crossbred sires (0.03 and 0.18).