Date of this Version
The indexes used in retrospect in estimating one-half genetic value (daughter superiority) of progeny of 541 Holstein matings contracted by Eastern Artificial Insemination Cooperative were determined. A set of information on relatives to be complete would include records of paternal sisters, the dam, paternal sisters of the dam, maternal sisters, maternal grandam, and maternal sisters of the dam. The average index of daughter superiority for the 541 progeny was between 406 and 455 kg of milk, depending on which combination of relatives was used. Paternal sisters accounted for 45 to 50% of the total daughter superiority. Records of maternal relatives, particularly records of the grandam and the dam, generally received too much emphasis relative to theoretical weights. The overemphasis on the dam's records may be due to the greater opportunity for selection of dams than for selection of sires. Efficiency of the indexes actually used in retrospect was computed as the ratio of the average correlation between the retrospective index and the true daughter superiority to average correlation between the index, using theoretical weights and true daughter superiority. The most efficient index in retrospect used records of paternal sisters, the dam, and paternal sisters of the dam, but was only 84% as efficient as the theoretically best index.