Phase-feeding to optimize performance and quality of Belgian Blue double-muscled bulls

To optimize performance and carcass quality of Belgian Blue double-muscled bulls four phased feeding regimens were evaluated. All diets were offered a d libitum and consisted of 650 g concentrates and 350 g maize silage per kg dry matter (DM). Total period was divided into three phases (ca. 360 to 46 0, 460 to 570 and 570 to 680 kg). All four groups received the same maize s ilage but the different energy and protein densities were applied using dif ferent concentrates. During the three phases, the negative control (NC) gro up constantly received a diet with a low protein and a moderate energy dens ity; the second group (DP) received with each phase diets with decreasing p rotein density while the energy density remained moderate; the third group (IE) received diets with increasing energy density at a constantly high pro tein density and the last group (DPIE) received diets which decreased in pr otein and increased in energy density. The NC group grew significantly slower during the first interval (1.37 v. 1 .62 kg/day for the other groups), resulting in a significantly longer total finishing period. During the third period IE had the slowest growth. The N C group needed 22 and 20 days move than the DP and DPIE groups, respectivel y, to reach the same slaughter weight. The NC group had the lowest DM intak e during the first interval, the IE group during the third interval. No sig nificant differences (P > 0.05) were found for food conversion, when expres sed as DM or NEF (net energy for fattening). IE had the worst protein conve rsion while NC had the best, with the two other groups being intermediate. The only important significant difference concerning carcass quality was th e improved dressing proportion of the IE and DP groups. Although significan t, differences in the Jot content of the m. longissimus thoracis are of min or importance. These results proved that for Belgian Blue double-muscled bu lls, protein density of the diet can be decreased with increasing live weig ht, while energy should be increased to give optimal performance.