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 materna l effects may occur when sire x year interaction (SY) effects are igno red in analytical models used to estimate (co)variance components for weaning weight in beef cattle. Using simulation, sire misidentificatio n was explored as a source contributing to estimates of SY valiance. I dentifications were falsified for 20% of sires of nonparents only or f or 20% of sires of all animals. Sire misidentification influenced esti mates of genetic and environmental parameters. In populations in which misidentification occurred only in nonparents, herita bility estimate s for direct growth were reduced, and heritability estimates of matern al effects were inflated. Also, spurious SY variance and direct-matern al covariance were produced. Direct-maternal covariance was biased in a positive direction, and SY variance was on the order of 1 to 3% of t he phenotypic variance.