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Analysis of the USDA-DHIA Preliminary Sire Summary

Animal Physiology and Genetics Institute, ARS, USDA, Beltsville, MD 20705

ABSTRACT

The first two USDA-DHIA Preliminary Sire Summaries were compared with official summaries on the same bulls. Preliminary summaries were available an average of 6.0 and 5.5 mo before official summaries. For six breeds, correlations between preliminary and official Predicted Differences for milk ranged from .93 to .98 for the June, 1973, preliminary and .96 to .99 for the October summary. Corresponding regressions of official Predicted Difference on preliminary Predicted Difference ranged from .89 to 1.09 and .99 to 1.05 for milk. The average absolute differences in Predicted Difference for milk varied directly with breed yield so were largest for Holsteins (35 and 27 kg). The accuracy of current projection factors appears to vary with season of calving, but this variation did not affect seriously sire selection based on records deviated from herdmates. Selecting young bulls on the preliminary evaluation may increase the rate of genetic improvement in sires by as much as 10%.