Genetic parameters for carcass, growth and reproductive traits in crossbred beef cattle

Carcass data on 4097 steers, reproductive data on 3361 first-calf heifers and growth data on 25809 males and females were used to estimate genetic parameters for crossbred cattle. Direct heritabilities for birth (BWT) and yearling weight (YWT) were higher than previously reported. Estimated heritabilities for weaning weight (WWT) and carcass traits were consistent with existing literature. Estimated genetic correlations between direct BWT, WWT and YWT and hot carcass weight (HCWT) were high and positive. Estimated genetic correlations between HCWT and maternal components of BWT and YWT were low but high and positive for WWT. Estimates of genetic correlations between carcass traits and maternal BWT and YWT were generally low but moderate with maternal WWT. Direct effects of BWT were positively associated with bone percentage (BONP) and ribeye area (REA) and negatively correlated with fat percentage (FATP) and adjusted fat thickness (AFAT). Direct effects of WWT were positively correlated with REA, AFAT and kidney, pelvic and heart fat percentage (KPH). Maternal effects of WWT were positively correlated with FATP, AFAT, marbling (MARB), REA and KPH and negatively correlated with retail product percentage (RETP). Direct effects of YWT were positively correlated with REA, FATP, AFAT and MARB and negatively correlated with RETP. Genetic correlations between direct and maternal components of growth traits and shear force (SHR) were low. Heritability estimates for calving difficulty (DIFF), calving rate (CRATE) and weaning rate (WRATE) were estimated using linear and threshold models and alternative computational algorithms. Heritability estimates were small and similar across models and methods. Genetic correlations between DIFF, CRATE and WRATE and carcass traits were near zero, except for DIFF with MARB (−.19) and WRATE with BONP (−.37) and RETP (−.21). Selection for improved carcass merit is not expected to significantly alter maternal ability for growth or reproductive traits, although BWT may be increased. Selection for direct WWT or YWT may be associated with favorable responses in REA, increased carcass fatness and decreased lean percentage.