Different sources of biochar had no effect on in vitro rumen fermentation and methane production.

It is been recommended to use biochar to amend soil characteristics and mitigate soil methane and nitrous oxide emissions. Adding biochar to ruminants feed may mitigate enteric and manure methane emissions. However, effect of biochar on rumen fermentation is not consistent in scientific literature, with responses depending on different factors, including source of biochar. The objective of this study was to examine the impact of different sources and levels of biochar on rumen microbial fermentation in vitro (24-h batch cultures). Biochar Happy tummy (rice husks, Fine Fettle, Narberth, UK), Airex (forest biomass, Airex, Bécancour, QC, Canada), Local-R and Local-L (black spruce, Agrinova, Alma, QC, Canada) were added at 1%, 2% and 5% of total mixed ration dry matter (DM). A negative (CTL, 0% biochar) and a positive (10 mg/L Monensin) control were used as response references. In vitro incubations (using 200 mg total mixed ration and 20 mL buffered rumen fluid) were repeated 3 times (3 runs) and conducted in a completely randomized block design. Each treatment was tested in triplicates within each run. The total mixed ration contained 32.1% NDF, 16.9% CP and 17.3% starch. Differences between treatments and CTL were declared significant at P ≤ 0.05 using Dunnett’s comparison test. Regardless of the source and level of biochar, total gas production and methane production were not affected and averaged (mean ± SD) 48.7 ± 1.57 mL and 8.7 ± 0.41 mL, respectively. No effects of biochar were observed on total VFA concentration or molar proportions of acetate, propionate, butyrate, or the acetate: propionate ratio. Use of Monensin (positive control) reduced methane production and acetate: propionate ratio in the buffered rumen fluid. It is concluded that adding increasing levels (up to 5% DM) of different biochar types tested in this study did not affect total VFA or methane production in vitro.