Data for a total of 3715 cattle from four sources were used to examine the relative importance of live weight at slaughter, and visual assessments of carcass conformation and subcutaneous fat cover, as predictors of killing out. The sources were the Meat and Livestock Commission's beef breed evaluation programme (1689 steers of different breeds and crosses), the beef demonstration unit at the National Agricultural Centre, Stoneleigh (814 commercial dairy-bred cattle), an East Anglian abattoir (405 commercial cattle) and the Milk Marketing Board's Warren Farm (807 dairy-bred steers by different sire breeds). An assessment of live body conformation was also examined as a predictor in the Warren Farm data.
Carcass conformation provided a more precise prediction of killing out than did either live weight or subcutaneous fat score. Regression coefficients in the different groups ranged from 5·4 to 12·0 g/kg for each increase in conformation class (six-point scale). The live conformation assessment was a less precise predictor (within sire breed residual s.d. = 17·7 g/kg) than the carcass assessment (15·6 g/kg).