Examination of More Frequent Genetic Evaluations for Dairy Bulls

Animal Improvement Programs Laboratory, ARS, USDA, Beltsville, MD 20705-2350

ABSTRACT Genetic evaluations of Holstein bulls for February 1997 through May 1998 were examined to determine the value of more frequent evaluation for quicker identification of bulls with changing predicted transmitting abilities (PTA) and of new bulls of superior genetic merit. Changes in PTA between evaluations that were calculated quarterly rather than semiannually were reduced by 30%. About two-thirds of PTA were closer to PTA that were calculated 3 mo later than were PTA calculated 3 mo earlier. Improvements in accuracy were 94 to 96% for a subset of bulls with substantial PTA changes from 3 mo before to 3 mo after an evaluation. With quarterly evaluation, half of the bulls had initial PTA available 3 mo sooner than with semiannual evaluation, and those PTA were better predictors of later PTA than were the parent averages that would have remained the best genetic estimates for 3 mo longer. Correlations of parent averages with PTA about a year later were 0.5 to 0.6, whereas correlations with later PTA were about 0.8 for initial PTA and 0.9 for second PTA. Although later PTA are expected to be improved estimates of true genetic merit, the timely results provided by quarterly evaluation were useful in identifying bulls with PTA that changed substantially and in identifying top new bulls.

(Key Words: genetic evaluation, evaluation frequency)

1999 J. Dairy Sci. 82:2766-2770

© 1999, by the American Dairy Science Association. All rights reserved.