Influence of sire misidentification on sire x year interaction variance and direct-maternal genetic covariance for weaning weight in beef cattle.

Biased estimates of the genetic correlation between direct and maternal effects may occur when sire x year interaction (SY) effects are ignored in analytical models used to estimate (co)variance components for weaning weight in beef cattle. Using simulation, sire misidentification was explored as a source contributing to estimates of SY variance. Identifications were falsified for 20% of sires of nonparents only or for 20% of sires of all animals. Sire misidentification influenced estimates of genetic and environmental parameters. In populations in which misidentification occurred only in nonparents, heritability estimates for direct growth were reduced, and heritability estimates of maternal effects were inflated. Also, spurious SY variance and direct-maternal covariance were produced. Direct-maternal covariance was biased in a positive direction, and SY variance was on the order of 1 to 3% of the phenotypic variance.