The influence of dietary energy and protein levels on performance, carcass and meat quality of Belgian White-blue double-muscled finishing bulls

Abstract

AbstractThe effect of three protein (77, 97 and 117 g DVE (true protein digested in the small intestine) per kg dry matter (DM)) and two energy levels (7·38 and 8·03 MJ NEF (net energy for fattening) per kg DM) on the performance of Belgian White-blue double-muscled finishing bulls and on the quality of their carcasses and meat was investigated. The diet, offered ad libitum, consisted of 650 g/kg concentrates and 350 g/kg maize silage on DM basis.No significant influence was found of the energy level on the growth rate. The low protein level reduced live-weight gain, from 370 to 501 kg (1·43 kg on average v. 2·60 and 1·66 kg daily; P < 0·02). The growth rate during the entire period (370 to 692 kg) and the live weight at slaughter were significantly influenced by the protein content.The bulls given the high energy level lost less weight during the 20-h fasting period before slaughter. Their carcasses were classified with a higher fatness score and a better conformation. These carcasses had a higher fat content, while the proportion of bone in the carcass was lower than in the low energy groups. The cold carcass weight of the low protein groups (456 kg on average) was significantly smaller than that of the four other groups (470 kg on average). Although no differences between the six groups were found concerning the dressing proportion, this measurement was significantly influenced by the protein level (685 g/kg for low protein v. 692 for high protein). The SEUROP conformation was positively influenced by the protein and the energy level, while the fatness score was influenced only by the energy level (5·5 v. 6·0 for the low and the high energy level, respectively). Although the differences in conformation, fatness score and dressing proportion are significant, because of the small variation, the practical meaning is less important.