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Correlations were computed between first lactation milk records expressed as deviations from herd-mate averages of pairs of Holstein paternal half-sibs in the same and in different herds. These were compared to the comparable daughter-dam regressions. After correcting the daughter-dam regression for environmental correlation and change in variance from the dam to the daughter generation, both the daughter- dam and paternal half-sib estimates of heritability were about .34, which suggests that maternal genetic variance is. unimportant. This estimate is, however, higher than the .25 found from the paternal half-sib estimate from an analysis for variance components.
The comparison of the half-sib correlations where the pair was in the same herd (.168) and in different herds (.086) suggests that the environmental correlation among paternal half-sibs in the same herds is about .08 of the total variance. There was no evidence that this environmental correlation is less for pairs of artificially sired than for naturally sired paternal half-sisters in the same herd.