Effects of dietary protein and energy on the growth of friesian bull calves

Abstract

In a 49-day comparative slaughter experiment with pre-ruminant calves, the effects of diets containing a range of protein: energy ratios and fed at two rates were examined relative to body composition at slaughter, and to the composition of weight gains made over this period. Groups of three Friesian bull calves were allocated to each of six milk-based rations containing either 15.7, 18.1, 21.8, 25.4, 29.6, or 31.5% protein (DM basis) and fed sufficient energy (21.6 ± 1.0 MJ/day) for live-weight gains of 830 g/day. The same diets, except for that containing 29.6% protein, were also fed to groups of three calves at energy intakes (17.4 ± 0.4 MJ/day) sufficient for live-weight gains of 610 g/day. Increasing dietary protein concentration significantly increased the contents of water and protein, and decreased the content of fat in the digesta-free bodies. These effects were more pronounced relative to body-weight gains during the trial. The higher feeding level significantly increased the percentage of fat and decreased the percentage of water in the body. The energy content of the digesta-free body weight gained during the trial decreased from 12.37 MJ/kg on the 15.7% protein diet to 9.31 MJ/kg on the 31.5% protein diet. The proportions of energy retained as fat on these diets were 70% and 51% respectively. © 1976 Taylor & Francis Group, LLC.