Relative Selection Efficiency in Retrospect of Selected Young Sires

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Abstract
The indexes used in retrospect in esti- mating one-half genetle value (daughter superiority) of progeny of 541 Holstein rantings contracted by Eastern Artificial Insemination Cooperative were determined. A set of information on relatives to be complete would include records of paternal sisters, the dana, 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 ac- counted for 45 to 50% of the total daugh- ter superiority. Records of maternal rela- tives, particularly records of the gran- dam 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 oppor- tunity for selection of dams than for se- lection of sires. Efficiency of the indexes actually used in retrospect was computed as the ratio of the average correlation be- tween the retrospective index and the true daughter superiority to average correla- tion 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.
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