RESULTS AND DISCUSSION
Polygenic Variation
Measures of growth to yearling age were lowly to
moderately heritable in the GPE Cycle VII population
(Table 1). Estimated using genotyped calves and observations
using ancestors, direct heritability of BWT was
approximately twice that of other BW or BW gains,
and the relative difference between PWG and BWT
was estimated to be more heritable than differences
including WG. Maternal influences on WW and WG
were greater than for other traits, with the proportion
of variance due to additive maternal or maternal permanent
environment effects at least as great as direct
additive variance. There was some additive maternal
influence on all traits except PWG. Direct heritability
of PWG, reestimated without maternal effects in the
model, was almost 50% greater than the estimate from
the model including maternal effects. Direct-maternal
genetic correlations were negative for birth and weaning
traits and positive for PWG and YW, but with