Reducing methane emissions from ruminant animals

In vitro and in vivo experiments were conducted to determine the effectiveness of lipids, exogenous fibrolytic enzymes, and the specific anti-methanogenic agent alpha-bromoedianesulfonic acid (BES) in reducing methane emissions from ruminant animals and their effect on dietary digestion. A rumen simulation technique system equipped with eight fermenters was used for in vitro investigations. Six ruminally and duodenally fistulated ewes were used for in vivo investigations.;Coconut, canola and cod liver oils (10% of diet, w/w) reduced (P < 0.05) methane emissions by 59, 26 and 29%, respectively, with a hay diet in in vitro studies. Comparative values with a concentrate diet were 85, 32 and 49% (P < 0.05). Coconut oil depressed (P < 0.05) dry matter (DM) digestion of the hay diet by 31%, but it had no influence on DM digestibility of the concentrate diet. Neither canola nor cod liver oil had any detrimental effect on the digestion of diets. Exogenous fibrolytic enzymes (4% of diet, wt/wt) increased (P < 0.01) methane emissions by 43% and organic matter (OM) digestibility by 9%. alpha-bromoethanesulfonic acid (25 muM) depressed (P < 0.01) methane emissions by up to 52% without a detrimental effect on digestion.;In the study with sheep, exogenous fibrolytic enzymes (1.5% of diet, vol/wt) or BES (200 muM) did not affect digestion, ruminal digestive kinetics, or methane emissions. Methane emissions (g/kg DMI) varied with intake of individual ewes, being about 20% lower (P < 0.05) at DM intake of 1.5 vs 0.6 kg/d. Similarly, methane emission (g/kg DMI) was decreased (P < 0.01) by 26% when apparent DM digestibility of the grass hay in the total tract increased from 36 to 57%. Diaminopimelic acid outflow to the duodenum (g/kg ruminally digested OM) and methane emissions (g/kg ruminally digested OM) decreased (P < 0.0001) by 67 and 64%, respectively, when apparent OM digestibility of grass hay in the rumen of ewes increased from 16 to 40%.;It was concluded that supplementation of lipids and BES effectively depressed methane emissions in vitro, but BES had no influence on methane emissions in sheep. Exogenous fibrolytic enzymes effectively increased forage digestion and methane emissions in vitro, but it had no effect on either forage digestion or methane emissions in sheep. Further studies are required with a more potent anti-methanogenic agent(s) to examine the relationship between methanogensis and microbial growth and dietary fermentation in the rumen.