Methane production is reduced in an in vitro incubation when the rumen fluid is taken from cattle that previously received biochar in their diet

In an 'in vitro' incubation the treatments in a 2*2 factorial arrangement were: rumen fluid from cattle previously fed biochar (BA), rumen fluid from cattle previously fed biochar + biochar added to the substrate (BA+BC), rumen fluid from cattle not previously fed biochar (NBA) and rumen fluid from cattle not previously fed biochar + biochar added to the substrate (NBA+BC). There were 4 replications of each treatment. The substrate contained (DM basis): 70% cassava root meal, 26.5-28% cassava leaf meal and 2% urea. In treatments BA+BC and NBA+BC the biochar was added at 1.5% of the substrate DM. These ingredients were mixed together in the incubation flask to which was added 480 ml of buffer solution and 120 ml of strained rumen fluid taken by stomach tube from cattle fed cassava root, cassava foliage and urea and either biochar (0.62% of diet DM) (for BA treatments) or no biochar (treatments NBA). Gas production and percentage substrate DM solubilized were increased, and percent methane in the gas was reduced, when: (i) the rumen fluid in the incubation flask was taken from cattle adapted to 0.62% biochar in their diet (DM basis) over a 4 month period; and (ii) when biochar was added to the incubation medium at 1.5% of DM. There were additive effects on methane reduction when rumen fluid from adapted cattle was combined with biochar added to the incubation medium.