Prediction of empty body components in steers by urea dilution.

Empty body composition of 68 mixed-breed and 50 Angus steers was determined by chemical analysis of the right half-carcass and entire noncarcass fraction of each steer. Chemical composition was used to develop prediction equations for empty body protein (EBPRO) and fat (EBFAT) in steers using urea space (US) and body weight measurements. Previous research showed a significant positive correlation between empty body water (EBH2O) and urea space in these steers. For all steers studied, the percentage of EBH2O ranged from 44.8 to 69.2 (mean = 56.0), the percentage of EBPRO ranged from 14.1 to 19.8 (mean = 17.0) and the percentage of EBFAT ranged from 6.1 to 38.1 (mean = 22.1). The best predictions obtained were multiple regression equations with actual weight of body components as dependent variables and US and empty body weight (EB) as independent variables. Urea space alone was a poor predictor of EBFAT, but US improved predictions based on live weight (LW) or EB alone. Coefficients of determination for the best predictions of percentage of composition were not as high as coefficients of determination for the best predictions of actual weight of body components. These data suggest that US measurements can be used to predict empty body composition of live steers, but this may require repeated measurements and an independent estimate of EB from LW for greatest accuracy.