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.