Phase-feeding to optimize performance and quality of Belgian Blue double-muscled bulls.
Four phased-feeding regimes were evaluated using 104 double-muscled Belgian Blue bulls. All diets were offered ad libitum and consisted of 650 g concentrates and 350 g maize silage/kg DM. The experiment was divided into 3 phases (approximately 360-460, 460-570 and 570-680 kg liveweight). Cattle on all regimes received the same maize silage but a different overall energy and protein density obtained from different concentrates. During the 3 phases, the negative control (NC) group constantly received a diet with a low protein and a moderate energy density; the second group (DP) received, in successive phases, diets with decreasing protein density while the energy density remained moderate; the third group (IE) received diets with increasing energy density at a constantly high protein density and the fourth group (DPIE) received diets which decreased in protein and increased in energy density through successive phases. The NC group grew significantly more slowly during the first phase (1.37 vs. 1.62 kg/day for the other groups), resulting in a significantly longer total finishing period. During the third phase, IE had the slowest growth. The NC group needed 21 and 20 days more than the DP and DPIE groups, respectively to reach the same slaughter weight. The NC group had the lowest DM intake during the first phase, and the IE group had the lowest DM intake during the third phase. No significant differences were found for feed conversion, when expressed as DM or NE for finishing. IE had the worst, and NC the best, protein conversion. The only significant difference in carcass quality was the higher dressing percentage of the IE and DP groups. Although significant, differences in the fat content of the longissimus thoracis muscle were of minor importance. The results showed that for double-muscled Belgian Blue bulls, the protein density of the diet can be decreased with increasing liveweight, while energy density should be increased to optimize performance.