Methane emission, nitrogen and energy utilisation of beef cattle when replacing or omitting soybean meal in a forage-based diet

Replacing imported soybean meal (SBM) by domestic protein sources such as grain legumes, food industry by-products or novel resource-efficient feeds is a current research focus to enhance the sustainability of ruminant production systems. In addition, grass silage replacing maize can contribute dietary crude (CP) supply well and complies with natural diet ruminants. An experiment 30 Limousin-sired beef bulls was performed diets in which SBM replaced alternative when feeding composed of, per kg dry matter (DM), 500 g silage, 300 200 concentrate. concentrate, (control diet) faba beans, pumpkin seed cake, spirulina (Arthrospira platensis) result on average 226 CP/kg concentrate (DM). A fifth group served negative control, received grain-based only 135 DM. Bulls were fed experimental for entire fattening period starting from an initial body weight (BW) 164 ± 2.3 4.3 0.06 months age. At 275 5.6 7.4 0.17 age, each animal underwent 9-day sampling determine individual N energy intake excretion (7 days urine faeces collection) methane emission (2 respiration chambers). The had no effect DM nutrient intake. Apparent fibre digestibility significantly affected diet, being numerically lowest beans instead SBM. Compared other groups, additional urinary (25.1 vs. 40.3 g/bull/day; 366 460 g/kg total faecal N). Digestive metabolic utilisation comparable among diets. Methane (CH4) adjusted differed highest (547 513 mg CH4/kg BW/day diets). These results show that none tested sources, including SBM, benefit containing complemented Feeding seems provide adequate metabolisable protein. Omitting common supplementation therefore mitigated losses thus likely emissions manure at unchanged utilisation.