Effect of feed additives on ruminal methanogenesis and anaerobic fermentation of manure in cows and steers

The inhibition of enteric methanogenesis using feed additives and anaerobic fermentation of animal manure to renewable energy is beneficial for the environment and to the producers. Two experiments were conducted using 4 steers and 4 cows in double 4 × 4 Latin square designs to investigate the potential effect of various feed additives on enteric and manure derived methanogenesis. In experiment 1, steers were offered high concentrate diets (80% concentrate and 20% hay) ad libitum with or without monensin, galacto-oligosaccharides (GOS) or l-cysteine. In experiment 2, cows were offered a diet (35% oat straw, 35% alfalfa hay cubes and 30% concentrates) at 76 g/kg BW0.75 daily with or without GOS, yeast culture (YC) or a mixture of GOS and YC. Steers that received monensin and GOS-containing diets had lower enteric CH4 missions. Digesters at 55 °C that were filled with manure from steers fed on monensin containing diets delayed in the initial CH4 production. However, after 40 days, CH4 production increased in digesters filled with monensin-containing manure. Monensin is a strong inhibitor of enteric methanogenesis, but has a negative influence on biogas energy production at short retention times.