Abstract
Variance and covariance components were estimated for birth and weaning weight from Limousin and Brangus field data for use in the reduced animal mixed model equations for a maternally influenced trait. Estimates of direct genetic variance (σ̂2A), maternal additive genetic variance (σ̂2M), covariance between direct and maternal additive genetic effects (σ̂AM), permanent maternal environmental variance (σ̂2PE) and residual variance (σ̂2∈) were calculated by equating variances estimated from a sire and dam model and a sire and maternal grandsire model to their expectations. The estimates for birth weight were σ̂2A, 2.10 and 4.62 kg2; σ̂AM, −.17 and −.39 kg2; σ̂2M, .53 and 2.40 kg2; σ̂2PE, .47 and −.02 kg2 and σ̂2∈, 6.78 and 11.99 kg2 for the Limousin and Brangus breeds, respectively. Estimates for weaning weight were σ̂2A, 63.94 and 163.52 kg2; σAM, −18.65 and −40.32 kg2; σ̂2M, 61.67 and 115.68 kg2; σ̂2PE, 23.70 and 24.00 kg2 and σ̂2∈, 269.58 and 320.21 kg2 for the Limousin and Brangus breeds, respectively. A description of the methodology for deriving the equations needed to estimate variances and covariances from a sire and maternal grandsire model for a single trait using expectations of quadratics formed from approximate sire and maternal grandsire solutions is presented. Copyright © 1987. American Society of Animal Science . Copyright 1987 by American Society of Animal Science.