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 h eifers (n = 957) were used to estimate genetic parameters and to investigat e the efficacy of maternal effects and preweaning growth information for im proving estimation of EBV for carcass traits for crossbred beef cattle. Dam s (n = 775) representing three F-1 and twelve back-cross combinations invol ving the Charolais, Hereford, Angus, Simmental and Shorthorn breeds were ma ted over six years to Limousin bulls (n = 36) at two locations in western C anada. Four animal models, involving from zero to three maternal (co)varian ces 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, an d were 0.20, 0.35, 0.50 and 0.38 for hot carcass weight, fat thickness, rib eye area and percent lean yield, respectively. Maternal heritabilities were 0.21, 0.22 and 0.40 for birth weight, preweaning daily gain and weaning we ight, respectively. Estimated genetic correlations between percent lean yie ld 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) corre lations with direct effects for carcass weight, ribeye area and percent lea n yield. Direct genetic effects for fat thickness were negatively correlate d with direct effects for birth weight (-0.44), preweaning daily gain (-0.1 5) and weaning weight (-0.25). Maternal genetic effects for preweaning trai ts had near-zero correlations with direct genetic effects far fat thickness and percent lean yield. Adding preweaning growth information to genetic ev aluations for carcass traits slightly decreased prediction error variances for breeding values and would be recommended when information on carcass tr aits is limited.