Responses in digestion, rumen fermentation and microbial populations to inhibition of methane formation by a halogenated methane analogue

Abstract

The effects of the anti-methanogenic compound, bromochloromethane (BCM), on rumen microbial fermentation and ecology were examined in vivo. Japanese goats were fed a diet of 50 % Timothy grass and 50 % concentrate and then sequentially adapted to low, mid and high doses of BCM. The goats were placed into the respiration chambers for analysis of rumen microbial function and methane and H 2 production. The levels of methane production were reduced by 5, 71 and 91 %, and H 2 production was estimated at 545, 2941 and 3496 mmol/head per d, in response to low, mid and high doses of BCM, respectively, with no effect on maintenance feed intake and digestibility. Real-time PCR quantification of microbial groups showed a significant decrease relative to controls in abundance of methanogens and rumen fungi, whereas there were increases in Prevotella spp. and Fibrobacter succinogenes, a decrease in Ruminococcus albus and R. flavefaciens was unchanged. The numbers of protozoa were also unaffected. Denaturing gradient gel electrophoresis and quantitative PCR analysis revealed that several Prevotella spp. were the bacteria that increased most in response to BCM treatment. It is concluded that the methane-inhibited rumen adapts to high hydrogen levels by shifting fermentation to propionate via Prevotella spp., but the majority of metabolic hydrogen is expelled as H 2 gas.Key words: Rumen: Methane: Hydrogen: Bromochloromethane: Goats Enteric fermentation in livestock accounts for 19 % of anthropogenic sources of methane, a potent greenhouse gas (1) , for which rumen fermentation is the largest source of methane production. In rumen fermentation, several pathways involving both hydrogen-producing and -consuming steps are involved in the conversion of feedstuffs into various fermentation end products such as SCFA (2,3) . Although metabolic hydrogen in the rumen is incorporated in fermentation end products by bacteria, methanogenic archaea (methanogens) consume the greater majority of metabolic hydrogen to obtain energy for their metabolism and finally release methane, which accounts for 2 -12 % loss of the metabolic energy from feed (1,3,4) . Therefore, management of metabolic hydrogen and methane production in the rumen is an important factor to be considered, when developing strategies to reduce greenhouse gas emissions and improve efficiency of energy utilisation from feed.It is known that many chemical agents such as ionophores (e.g. monensin), unsaturated fatty acids, sulphate, nitrate, fumarate and halogenated methane analogues (e.g. bromochloromethane (BCM)) are able to reduce methane production from ruminants (1,4 -6) . BCM is one of the most effective inhibitors and apparently reduces methane production by interfering with the cobamide-dependent methyl transferase step of methanogenesis (7,8) . BCM complexed in cyclodextrin (CD; BCM-CD) results in the sustained inhibition of methane production when fed to ruminants (9 -11) . Moreover, an in vitro continuous fermentation system simulating rumen fermentation demon...

Interactions between microbial consortia in biofilms: a paradigm shift in rumen microbial ecology and enteric methane mitigation

“…Addition of BCM to rumen contents in vitro, or to the rumen directly, strongly inhibited CH 4 production (McCrabb et al 1997;Goel et al 2009;Mitsumori et al 2012). The most successful compounds tested in vivo have been the chlorinated hydrocarbons, including BCM, 2-bromoethane sulfonate (BES), chloroform and cyclodextrin.…”

“…McCrabb et al 1997). Surprisingly, with this type of inhibition, there is no reduction in feed digestibility or production and the reduction in CH 4 release is accompanied by a concomitant stoichiometric production of H 2 (Mitsumori et al 2012). If it is assumed that the H 2 is produced in fermentative sites in the biofilm, it is reasonable to expect an increased partial pressure of H 2 at these sites and, therefore, adverse effects on feed digestion and intake.…”

Development of Multiwell-Plate Methods Using Pure Cultures of Methanogens To Identify New Inhibitors for Suppressing Ruminant Methane Emissions

“…Although some of these strategies have shown promise, not all directly target methanogens. Halogenated compounds (e.g., chloroform and bromochloromethane) are highly potent inhibitors of methanogenesis in ruminants (6,(16)(17)(18)(19)(20)(21). However, these compounds are not considered appropriate for use in current animal husbandry due to environmental, human health, and animal welfare concerns.…”

Bromochloromethane, a Methane Analogue, Affects the Microbiota and Metabolic Profiles of the Rat Gastrointestinal Tract

“…BCM supplementation at 0.3 g/100 kg of body weight (BW) significantly decreased methane production and methanogen abundance in Japanese goats (5), lactating dairy goats (6), steers (7), and Sprague-Dawley (SD) rats (8). BCM inhibits methanogenesis by reacting with cobalamin (9).…”