ABSTRACT Genetic evaluations for the length of productive life
based on actual DHIA culling data have been available in the US since January
1994. Although substantial genetic variation in productive life exists,
the reliability of selection is often low, particularly for recently progeny-tested
bulls having daughters that have not yet had an opportunity to be culled.
Correlated production and conformation traits, which have higher heritability
than productive life and are available earlier in life, may be used to
enhance evaluations of productive life for young bulls that have little
or no direct culling information available. Genetic correlations between
productive life and milk, fat, dairy form, and udder traits ranged from
+0.22 to +0.46. The maximum reliability of the indirect prediction of productive
life from 16 correlated type and production traits was 0.56, and the maximum
reliability from a subset of 10 traits was 0.51. Indirect information about
productive life that was derived from type and production traits was combined
with actual culling information to increase the total amount of available
information for many recently progeny-tested bulls. The procedures described
herein for enhancing direct evaluations for the productive life of dairy
sires with indirect information about production and type were implemented
by the USDA Animal Improvement Programs Laboratory and the Holstein Association
USA in July 1994.