Methane mitigation in ruminants: from microbe to the farm scale

Abstract

Decreasing enteric methane (CH 4 ) emissions from ruminants without altering animal production is desirable both as a strategy to reduce global greenhouse gas (GHG) emissions and as a means of improving feed conversion efficiency. The aim of this paper is to provide an update on a selection of proved and potential strategies to mitigate enteric CH 4 production by ruminants. Various biotechnologies are currently being explored with mixed results. Approaches to control methanogens through vaccination or the use of bacteriocins highlight the difficulty to modulate the rumen microbial ecosystem durably. The use of probiotics, i.e. acetogens and live yeasts, remains a potentially interesting approach, but results have been either unsatisfactory, not conclusive, or have yet to be confirmed in vivo. Elimination of the rumen protozoa to mitigate methanogenesis is promising, but this option should be carefully evaluated in terms of livestock performances. In addition, on-farm defaunation techniques are not available up to now. Several feed additives such as ionophores, organic acids and plant extracts have also been assayed. The potential use of plant extracts to reduce CH 4 is receiving a renewed interest as they are seen as a natural alternative to chemical additives and are well perceived by consumers. The response to tannin-and saponincontaining plant extracts is highly variable and more research is needed to assess the effectiveness and eventual presence of undesirable residues in animal products. Nutritional strategies to mitigate CH 4 emissions from ruminants are, without doubt, the most developed and ready to be applied in the field. Approaches presented in this paper involve interventions on the nature and amount of energy-based concentrates and forages, which constitute the main component of diets as well as the use of lipid supplements. The possible selection of animals based on low CH 4 production and more likely on their high efficiency of digestive processes is also addressed. Whatever the approach proposed, however, before practical solutions are applied in the field, the sustainability of CH 4 suppressing strategies is an important issue that has to be considered. The evaluation of different strategies, in terms of total GHG emissions for a given production system, is discussed.Keywords: methane, greenhouse gases, ruminant, mitigation strategies Implications Methane (CH 4 ) mitigation in ruminants is possible through various strategies. Today, the feeding management approach is the most developed. Other strategies (biotechnologies, additives) are promising but the diversity and plasticity of functions of the rumen bacterial and methanogenic communities may be a limiting factor for their successful application. A possible selection of animals on CH 4 production and more likely on digestive processes is evocated. In any case, before practical solutions are proposed for field application more research in vivo is needed. The sustainability of CH 4 -suppressing strategies is also an important issue and they mi...

An evaluation of the accuracy and precision of methane prediction equations for beef cattle fed high-forage and high-grain diets

“…The ED computed for equation N was lower than obtained by Ellis et al (2009) (76.4% v. 95.8%, respectively). Fat content of diets, which is associated with lower CH 4 production (Martin et al, 2009), was not considered by any of the best-fit equations but may be indirectly considered by equations that include GEI, when GE content is measured directly rather than assumed to be constant.…”

Progress in the development of vaccines against rumen methanogens

“…A range of different strategies are being investigated to reduce methane emissions from farmed ruminants (reviewed by Martin et al, 2010;Buddle et al, 2011;Clark, 2013). Vaccination of ruminants against rumen methanogens has the potential to reduce methane emissions by decreasing the number or activity of methanogens in the rumen.…”

Impact of adding nitrate or increasing the lipid content of two contrasting diets on blood methaemoglobin and performance of two breeds of finishing beef steers

“…Increasing the concentration of dietary lipid has been shown to reduce CH 4 emissions from ruminants (Martin et al, 2010;Grainger and Beauchemin, 2011;Patra, 2013). This is achieved through various mechanisms: fatty acids are not fermented in the rumen and therefore increasing dietary lipid concentration reduces the proportion of feed which is fermentable within the rumen; lipids can also reduce CH 4 production by coating fibre particles, reducing their digestibility, and by reducing the numbers and activity of the rumen methanogens and protozoa responsible for methanogenesis (Johnson and Johnson, 1995;Patra, 2013).…”

“…Although increased concentrations of dietary lipid has been shown to reduce CH 4 from ruminants (Martin et al, 2010;Grainger and Beauchemin, 2011;Patra, 2013), at high concentrations in the diet lipid can negatively affect DMI and productivity (Brask et al, 2013). Based on a meta-analysis, Patra (2013) demonstrated that dietary lipid concentrations in excess of 6% cause problems with productivity.…”