Redirecting rumen fermentation to reduce methanogenesis

Abstract

IMPF: 00.81 RONO: 00Methane production in ruminants has received global attention in relation to its contribution to the greenhouse gas effect and global warming. In the last two decades, research programs in Europe, Oceania and North America have explored a variety of approaches to redirecting reducing equivalents towards other reductive substrates as a means of decreasing methane production in ruminants. Some approaches such as vaccination, biocontrols (bacteriophage, bacteriocins) and chemical inhibitors directly target methanogens. Other approaches, such as defaunation, diet manipulations including various plant extracts or organic acids, and promotion of acetogenic populations, seek to lower the supply of metabolic hydrogen to methanogens. The microbial ecology of the rumen ecosystem is exceedingly complex and the ability of this system to efficiently convert complex carbohydrates to fermentable sugars is in part due to the effective disposal of H2 through reduction of CO2 to methane by methanogens. Although methane production can be inhibited for short periods, the ecology of the system is such that it frequently reverts back to initial levels of methane production though a variety of adaptive mechanisms. Hydrogen flow in the rumen can be modelled stoichiometrically, but accounting for H2 by direct measurement of reduced substrates often does not concur with the predictions of stoichiometric models. Clearly, substantial gaps remain in our knowledge of the intricacies of hydrogen flow within the ruminal ecosystem. Further characterisation of the fundamental microbial biochemistry of hydrogen generation and methane production in the rumen may provide insight for development of effective strategies for reducing methane emissions from ruminants.Peer reviewe

Methane mitigation in ruminants: from microbe to the farm scale

“…This was attributed to the toxicity of organosulphur compounds such as diallyl sulphide and allicin on methanogens. This effect was corroborated for allicin by quantitative PCR (McAllister and Newbold, 2008). Additional research in vivo is required to determine the optimal dose of the active compounds, to consider the potential adaptation of rumen microbes, the presence of residues in animal products as well as the potential anti-nutritional side-effects of such molecules (reviewed by Calsamiglia et al, 2007).…”

“…Moss et al, 2000; Boadi et al, 2004;Newbold and Rode, 2006;Beauchemin et al, 2008;McAllister and Newbold, 2008). Owing to the importance and the rapid evolution of knowledge in this research area, we present in this paper an updated review of proved and some potential mitigation options, together with their known mode of action.…”

“…The effect of rumen protozoa on CH 4 production and on methanogens has been recently investigated by molecular biology. The decrease in CH 4 production of 26% per kg of dry matter intake (DMI) in protozoa-free lambs was related to a decrease in the proportion of methanogens in the total bacterial population of the whole ruminal content (reviewed by McAllister and Newbold, 2008). In another study, whereas CH 4 production significantly decreased by 20% in protozoa-free sheep, from 41 l per animal per day in the presence of protozoa to 34 l per animal per day , the quantity of methanogens estimated by quantitative PCR as well as their diversity estimated by Enteric methane mitigation strategies in ruminants 353 PCR-denaturing gradient gel electrophoresis was not different between faunated and defaunated animals (Mosoni et al, 2008a), suggesting that the decreased methanogenesis might be due to a reduction in the amount of hydrogen substrate.…”

Effects of long-term supplementation of chestnut and valonea extracts on methane release, digestibility and nitrogen excretion in sheep

“…Methane production can be reduced by different means, including plant constituents such as saponins and tannins (Van Nevel, 1996;McAllister and Newbold, 2008;Hook et al, 2010). Tannins -a fraction of polyphenols in plantsare generally divided into condensed (CT) and hydrolysable (HT) tannins.…”

“…Tannins may have anti-nutritive effects (Reed, 1995), which are assumed to be mainly associated with HT (MuellerHarvey, 2006;McAllister and Newbold, 2008) suggesting that only CT are suitable for use in animals. Hence, research on the influence of tannins on the release of methane has mainly focused on CT.…”