Lipid-induced depression of methane production and digestibility in the artificial rumen system (RUSITEC)

An artificial rumen (RUSITEC) equipped with eight fermenters was used to examine the effects of canola oil (CA), cod liver oil (CD) and coconut oil (CO) on methane production, dietary digestibility and rumen microbial populations. The experiment, repeated three times, involved two diets (100% grass hay or a 90%:10% wheat:hay mixture) either untreated (controls) or sprayed with CA, CD or CO (10%, wt/wt) in a 2 × 4 factorial arrangement. Dry matter disappearance and CH4 production were greater (P < 0.05) from untreated concentrate diet than from untreated hay. There were significant interactions (P < 0.05) between diet and lipid type for DM digestion and several of the fermentation parameters. Coconut oil decreased (P < 0.05) DM and neutral detergent fibre disappearance of hay but did not affect digestion of concentrate. All oils, especially CO, depressed (P < 0.05) CH4 production (mmol g−1 digestible DM) and methanogenic populations regardless of diet. Methanogens on CO-treated diets numbered less than 1% ...