Predicting Daughter Milk Production from Dam Index

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Abstract
First lactations in Dairy Herd Improvement Associations from 10,349 registered Holsteins in Iowa, Kansas and Missouri [USA) were used to evaluate the usefulness of Estimated Average Transmitting Ability of dams to predict milk production of their future daughters where dam and daughter were in the same herd. This index estimates half the genetic worth of a cow from her records and records of her dam, daughters, paternal and maternal half sisters. Correlation of dam''s index with daughter deviated 1st lactation milk yield was .18 where .20 was expected. Linear regression of daughter 1st lactation deviated yield on dam index was 1.15, which differed from 1.00. Quadratic and cubic regressions were not significant, but daughters of the lowest dams produced more milk than expected. Deviated yield of daughter 1st lactation was regressed simultaneously on groups of relatives in the dam''s index. Weights for cow were larger than expected, and weights for dam were smaller than expected. Multiple correlations indicated dams and maternal sisters contributed less than expected to accuracy of predicting daughter yield.