EFFECT OF FEEDS AND GROWTH-RATE DURING THE GROWING PHASE ON SUBSEQUENT PERFORMANCE DURING THE FATTENING PERIOD AND CARCASS COMPOSITION IN YOUNG DAIRY BREED BULLS

Five consecutive experiments were undertaken to evaluate the respective effects of type of feed and growth rate during calfhood (5 to 11 months of age) on body composition and performance during the subsequent fattening period in young Friesian bulls. At a similar growth rate during calfhood, no difference was found between the feed treatments (maize silage, grass silage and pasture) in terms of subsequent feed intake, daily weight gain, feed efficiency during the fattening period, and carcass composition at a fixed slaughter weight. Dressing percentage, however, tended to be lower in bulls previously reared at pasture than in bulls previously fed silages. When given the same type of feed during calfhood and with an imposed reduction in growth rate, the bulls showed little compensatory growth during the fattening period, and the significant differences in body composition estimated at 1 year of age (viz. lower carcass fat) were no longer perceptible at slaughter at the same carcass weight. It was concluded that the type of food consumed during calfhood had practically no effect per se on the subsequent performances of early-maturing young bulls. The growth rate imposed before 1 year of age only affected the duration of the fattening period required to reach a fixed carcass weight.