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Prediction of Heifer Transmitting Ability from Genetic Evaluations of Sire, Dam, and Maternal Grandsire

Department of Animal Science, Cornell University, Ithaca, NY 14853

ABSTRACT

Estimated transmitting abilities for milk of 258,201 Holstein heifers from first lactations were regressed on sire's milk proof, maternal grandsire's milk proof, and either dam's estimated transmitting ability from milk in first lactation or dams's estimated transmitting ability from milk of all lactations. Effects of year of birth of dam, dam's estimated transmitting ability for milk from first lactation, for milk from all lactations, estimated transmitting ability for fat from first lactation or for fat from all lactations were determined by sorting data into deciles by each of these criteria and calculating partial regression coefficients within each decile. For data in deciles on dams's estimated transmitting ability for milk in first lactation, no further information was gained from all lactations. Partial regression coefficients from regression of heifer's estimated transmitting ability from first lactation on dam's estimated transmitting ability from first lactation, maternal grandsire's proof, and sire's proof were similar to approximate theoretical upper limits. The partial regression coefficient for dam's estimated transmitting ability from all lactations was much smaller than expected. Because regression on dam's estimated transmitting ability from first lactation resulted in weights more closely approximating theoretical upper limits than weights from regression on dam's estimated transmitting ability from all lactations, the use of the former is preferred to predict heifer's estimated transmitting ability from first lactation.