Contributions of preweaning growth information and maternal effects for prediction of carcass trait breeding values among crossbred beef cattle

Preweaning and carcass trait records from crossbred steers (n = 1015) and heifers (n = 957) were used to estimate genetic parameters and to investigate the efficacy of maternal effects and preweaning growth information for improving estimation of EBV for carcass traits for crossbred beef cattle. Dams (n = 775) representing three F-1 and twelve back-cross combinations involving the Charolais, Hereford, Angus, Simmental and Shorthorn breeds were mated over six years to Limousin bulls (n = 36) at two locations in western Canada. Four animal models, involving from zero to three maternal (co)variances were used to analyze four carcass traits. Rank and simple correlations indicated that maternal effects were relatively unimportant for estimation of direct carcass trait breeding values. Direct heritabilities were 0.28, 0.12 and 0.16 for birth weight, preweaning daily gain and weaning weight, and were 0.20, 0.35, 0.50 and 0.38 for hot carcass weight, fat thickness, ribeye area and percent lean yield, respectively. Maternal heritabilities were 0.21, 0.22 and 0.40 for birth weight, preweaning daily gain and weaning weight, respectively. Estimated genetic correlations between percent lean yield and hot carcass weight, fat thickness and ribeye area were -0.05, -0.85 and 0.39, respectively, and 0.30 between hot carcass weight and ribeye area. Direct genetic effects for birth weight had moderate (0.51 to 0.54) correlations with direct effects for carcass weight, ribeye area and percent lean yield. Direct genetic effects for fat thickness were negatively correlated with direct effects for birth weight (-0.44), preweaning daily gain (-0.15) and weaning weight (-0.25). Maternal genetic effects for preweaning traits had near-zero correlations with direct genetic effects far fat thickness and percent lean yield. Adding preweaning growth information to genetic evaluations for carcass traits slightly decreased prediction error variances for breeding values and would be recommended when information on carcass traits is limited.