Date of this Version
The regression of daughter on dam deviations of Holstein first-lactation milk production from herd-mate averages was computed for 38,440 pairs of records made in the same herd and for 10,256 pairs of records where the daughter was in one herd and the dam in another. The corresponding heritability estimates were .42 and .40, respectively, which suggest an environmental covariance of .01 between records of daughters and dams in the same herd. Other analyses were conducted for dams with two daughters with records where 1) both had records in the same herd as the dam, 2) only one had a record in the same herd as the dam, 3) the daughters were full sibs, in the same herd as the dam, 4) the daughters were full sibs, only one in the herd of the dam. These analyses also indicated no evidence for much environmental covariance between daughter and dam records in the same herd. The environmental covariance between records of maternal half-sisters in the same herd is apparently small, but the environmental covariance between records of full sibs in the same herd may be important - .06 to .12 of total variance. Genetic maternal variance was not excluded as a source of likeness between the records of maternal relatives.