Effects of by-products from biofuel production on the performance of growing fattening bulls

Due to the increased production of bioethanol and biodiesel, a considerable quantity of the remaining protein-rich by-products, such as rapeseed meal (RSM) and distillers dried grains with solubles (DDGS), is available for animal nutrition, but the diversity of production technologies leads to a wide variation of feed quality. The aim of the present study was to compare the use of RSM and DDGS with soybean meal (SBM) in diets for fattening bulls in order to investigate the effects on feed intake and performance parameters. Fifty-nine Holstein bulls (initial live weight 246 kg) divided into four groups received 0.5 kg/d of a mineral premix and maize silage for ad libitum intake. Furthermore the animals were offered either SBM (1.1 kg/d), RSM (1.5 kg/d), DDGS (1.6 kg/d) or RSM + DDGS (0.8 + 0.8 kg/d). The rations were formulated to be isonitrogenous and isoenergetic. Dry matter (DM) intake as well as live weight was measured individually. The mean live weight at slaughter was 558 kg. The crude protein content of the diets was 142, 140, 144 and 143 g/kg, and the daily DM intake amounted 7.5, 7.6, 7.7 and 8.0 kg, respectively. The daily weight gains were 1390, 1440, 1310 and 1460 g for animals fed with SBM, RSM, DDGS and RSM + DDGS, and were different only between DDGS and RSM + DDGS (P=0.018). The slaughtering results were not influenced by the protein source. It can be concluded that RSM and DDGS are suitable to replace SBM in diets for growing fattening bulls.