acetate alfalfa anaerobic digestion anaerobic respiration australia bacteria biofuel butyric acid california cattle claas jaguar cud electricity ensilage enterococcus faecium eutrophication fodder forage forage harvester grain crimping grass hay heat lactic acid lactic acid bacteria lactobacillus buchneri lactobacillus plantarum mb trac maize new zealand nitric acid nitrogen dioxide pediococcus propionate recycling ruminant sorghum stover tractor volatile fatty acids wikimedia commons