The Effects of Biochar and Fat Supplementation on Microbial Fermentation in Batch Cultures

Biochar is a byproduct formed by burning green waste for carbon sequestering in a process called pyrolysis. This product can be used as a soil amendment to benefit plant yield. It has also been used as a supplement for cattle, though benefits in ruminants are still being explored. Hansen et al. (2012) noted a numerical decrease in methane production in vitro. Ruminants erupt methane as a hydrogen sink in the reduced rumen environment. Without a way to remove hydrogen, the microbial ecosystem cannot function normally. Polyunsaturated fatty acids have been used to decrease methane production; however, they often depress NDF digestibility. Therefore, more research is necessary to confirm that decreasing methane production with biochar does not also result from depressing neutral detergent fiber (NDF) digestibility, a major component of dairy cattle diets. The objectives of this study were to observe NDF disappearance (NDFD), volatile fatty acid (VFA) production, and methane gas output with supplementation of a biochar product in rumen fluid batch cultures. The treatments (Trt) were biochar (BC) or biochar bolus (BCB, biochar with electrolytes). The diet provided was a high forage (HF) diet with concentrate pellets (33.3%), orchard grass (44.4%), alfalfa (22.2%), and either no supplemented fat or 3% dry matter (DM) as corn oil (CO). The BC and BCB were dosed (Inc) at either 0, 1, 2 or 4% of total DM. Separately, four round bottom flasks were used for gas production measurements because smaller culture tubes would not produce enough gas volume. The flasks were fed either HF or HF with BC at 2%. Data were analyzed utilizing PROC MIXED (v. 9.4, SAS Institute 2015) with the fixed effects of Trt, CO, Inc, and their interactions. The random effects were run and order of inoculation. BC did not decrease NDFD and with 2% - CO and 1% + CO NDFD increased. BCB also did not decrease NDFD and with 1% - CO, 4% - CO, and 1% + CO NDFD increased (P = 0.07, Trt*CO*Inc). For total VFA production, BC increased the concentration with 2% - CO, 4% - CO, and 4% + CO. BCB also increased total VFA with 4% - CO and 4% + CO (P = 0.02, Trt*CO*Inc). Although methane gas production was not significant, there was numerical reduction of 23.08 mg produced in 24 hours (P = 0.16). Methane (g/kg NDFD) decreased (P = 0.022) by 17.21 g/kg NDFD. A numerical decrease (P = 0.23) of 0.10 mg/d was also seen in hydrogen gas production. Therefore, BC could reduce methane output without depressing NDFD and VFA when implemented as a feed additive. With the current stress on agricultural practices to decrease environmental impacts, feeding biochar as a methane mitigation strategy could be crucial to the dairy industry while simultaneously utilizing a waste product.No embargoAcademic Major: Animal Science