Covariances Among First-Lactation Milk Records of Cousins

Covariances among first-lactation milk records expressed as deviations from herdmate averages of Holstein cows related as cousins of varying degree, as daughter-dan1, as full and maternal sibs, and as aunt-niece of varying degree were examined to dete~nine whether genetic maternal effects are important.The multiple regression of the expected coefficients of additive direct, additive maternal, dominance direct, and dominance maternal genetic variance components; and additive direct by additive maternal and dominance direct by dominance maternal genetic covariances on the 24 estimated covariances between pairs of relatives gave a multiple correlation coefficient of .95.The regression of actual covariance on the coefficient o£ additive direct genetic variance gave a correlation of .92.These results suggest for these data that only additive genetic effects are important for this trait.Additive genetic variance accounted for 38% of total variance.The intercept of the regression line indicated that the average environmental eovariance among pairs of relatives accounts for 2 to 3% of the total variance.