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Analysis of 60,000 pairs of daughter and dam first-lactation records expressed as deviations from herd-mate averages for five breeds yielded markedly different heritability estimates from daughter-dam regression than from paternal half-sib correlation. These results suggest that 18% of the within-herd variation is due to genetic maternal effects. The same records analyzed as mature equivalent records and not as deviations but by a sire by herd model did not show this difference. Confounding between year and sire effects probably biased the intraclass correlation estimates upward in the latter analysis, since year effects were not included in the statistical model.