Components of variance and covariance between direct and fetal effects in production traits

The correlation between sire of fetus effect and sire of cow effect on three production traits - milk yield, fat yield, and protein yield - in first lactation cows was investigated. Restricted maximum likelihood techniques were used. There was a small sire of fetus variance for milk yield, h2 .23%, while the sire of fetus variances for fat and protein were very small and negative. For milk yield the genetic correlation between sire of fetus effect and sire of cow effect was -.82. The negative sire of fetus variances for fat and protein precluded calculation of genetic correlations, both with sire of cow effects for fat and protein, and with each other and with milk yield for sire of fetus effects.