Weighting Information from Relatives to Select forMilk in Holsteins

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Abstract
Selection indexes to predict the general breeding values of individual Holsteins for milk production were developed from 7,638 deviations of first lactations from herd averages in a variety of combinations of the cow, her dam, daughters, and sisters. Heritability from the regression of paternal sisters on the cow was 0.246. The multiple correlation of the index with the cow''s genotype ranged from 0.50 to 0.73 depending on the kinds and amounts of information available from relatives. Selection by index was compared with mass selection on the cow''s own record in a test population of 429 Holstein cows and their 498 daughters. The first record of an unselected daughter was correlated with the cow''s index 0.166 and with the cow''s own first record 0.140 - an increase in accuracy of nearly 19% in favor of index selection. The index appears practical to increase genetic progress for milk production- especially to select dams of future sires.