A Pine Enhanced Biochar Does Not Decrease Enteric CH4 Emissions, but Alters the Rumen Microbiota

Abstract

The objective of this study was to examine the effect of a pine enhanced biochar (EB) on rumen fermentation, apparent total tract digestibility, methane (CH4) emissions, and the rumen and fecal microbiome of Angus × Hereford heifers fed a barley silage-based diet. The experiment was a replicated 4 × 4 Latin square using 8 ruminally cannulated heifers (565 ± 35 kg initial BW). The basal diet contained 60% barley silage, 35% barley grain and 5% mineral supplement with EB added at 0% (control), 0.5, 1.0, or 2.0% (DM basis). Each period lasted 28 days, consisting of 14 days adaptation and 14 days of measurements. Samples for profiling of the microbiome in rumen liquid, solids and feces were collected on d 15 before feeding. Rumen samples for fermentation characterization were taken at 0, 3, 6, and 12 h post feeding. Total collection of urine and feces was conducted from days 18 to 22. Heifers were housed in open-circuit respiratory chambers on days 26–28 to estimate CH4 emissions. Ruminal pH was recorded at 1-min intervals during CH4 measurements using indwelling pH loggers. Data were analyzed with the fixed effects of dietary treatment and random effects of square, heifer within square and period. Dry matter intake was similar across treatments (P = 0.21). Ammonia N concentration and protozoa counts responded quadratically (P = 0.01) to EB in which both were decreased by EB included at 0.5 and 1.0%, compared to the control and 2.0% EB. Minimum pH was increased (P = 0.04), and variation of pH was decreased (P = 0.03) by 2.0% EB. Total tract digestibility, N balance and CH4 production were not affected (P ≥ 0.17) by EB. Enhanced biochar decreased the relative abundance of Fibrobacter (P = 0.05) and Tenericutes (P = 0.01), and increased the relative abundance of Spirochaetaes (P = 0.01), Verrucomicrobia (P = 0.02), and Elusimicrobia (P = 0.02). Results suggest that at the examined concentrations, EB was ineffective at decreasing enteric CH4 emissions, but did alter specific rumen microbiota.

Feed additives as a strategic approach to reduce enteric methane production in cattle: modes of action, effectiveness and safety

“…Biochar supplemented at 8 g/kg DM reduced CH 4 production by 9.5% in growing steers and 18.4% in finishing steers (Winders et al 2019). Contrary to these findings, inclusion levels of 'pine-enhanced biochar' at 5, 10 and 20 g/kg DM in the diets of Angus • Hereford heifers did not reduce CH 4 emissions (Terry et al 2019). However, it altered the microbiota, notably selecting against Fibrobacter species, which is one of the dominating phyla of the rumen responsible for cellulose degradation (Béra-Maillet et al 2004).…”

“…Possible mechanisms have been elucidated through a study that observed that application of biochar to paddy soils stimulated methanotrophic proteobacteria and reduced CH 4 , despite methanogens also being stimulated (Feng et al 2012). Additionally, biochar may provide a habitat for methanogens or possibly absorb gases when consumed due to its porous nature, but the mechanisms of action for CH 4 mitigation in cattle are not well understood (Terry et al 2019;Man et al 2020).…”

Dose response of biochar and wood vinegar on in vitro batch culture ruminal fermentation using contrasting feed substrates

“…Yet, consistency seems an obvious barrier to definitive confirmation. Two recent papers ( Teoh et al, 2019 ; Terry et al, 2019 ) both used biochars with a pH similar to that applied in the current study (8.2, 7–8, and 8.4, respectively). All investigations reported no effect of the biochar on methane production.…”

Methane Emissions from Ruminants in Australia: Mitigation Potential and Applicability of Mitigation Strategies

“…Despite the positive indications from in vitro experiments and theory, recent experiments with cattle fed from 0.5% to 3% of the diet as biochar made from pinewood [ 114 ] or whole pine trees [ 115 ] have failed to show significant declines in methane emissions. These latter results suggest that biochar is unlikely to have a significant impact on methane mitigation from ruminants.…”