An evaluation of models predicting beef cattle performance using data from bulls on performance testing

Data from 372 bulls on performance testing were used to compare predictions of intake and gain with observed performance when the forage-to-concentrate ratio (F:C) in the ration ranged from 57:43 to 45:55. Predictions were derived from the National Research Council (NRC 1996) and the Agricultural and Food Research Council (AFRC 1993) models. Increasing the F:C resulted in a decline in dry matter intake as a percent of body weight, but did not influence observed average daily gain (ADG). The NRC (1996) model increasingly under-predicted ADG as forage inclusion in the ration increased, whereas AFRC (1993) was a better predictor of daily gain as F:C increased. Contrary to predictions, inclusion levels of silage can be increased in totally mixed rations without compromising animal performance. Key words: Forage-to-concentrate ratio, bulls, performance, model