Dietary mitigation of enteric methane from cattle.

Abstract

Enteric methane from ruminants accounts for about 11-17% of methane generated globally, or 17-30% of methane from human activity. Methane arises from the activity of methanogens in the rumen that use hydrogen to reduce carbon dioxide, thereby preventing the accumulation of reducing equivalents, which would otherwise impede ruminal fermentation. Although this process is desirable from a fermentation perspective, it is energetically costly, as cattle emit 2-12% of their gross energy intake in this potent greenhouse gas (GHG). Many production practices aimed at increasing efficiency of production, such as including grain and ionophores in diets, also lower methane emissions. These practices were adopted long before issues arose over the role of methane from livestock in climate change. Dietary inclusion of free oils or oil-rich feeds (e.g. oilseeds, distillers' grains and micro-algae), biologically active plant compounds (e.g. condensed tannins, saponins and essential oils), rumen fermentation modifiers (e.g. yeast and bacterial direct-fed microbials), as well as improvements in forage quality may allow for further reductions in methane emissions from cattle. The optimum dietary strategy will depend on the particular farm, its geographic location, the feedstuffs available and the type of animals being fed. Reductions can occur as decreased methane output per animal per day or as decreased methane output per kg of meat or milk produced, but ultimately, it seems prudent that mitigation practices be assessed on the basis of the extent to which they reduce methane emissions per kg of meat or milk produced. Furthermore, potential mitigation practices need to be assessed from the perspective of the entire life cycle, as a reduction in GHG in one sector of the production cycle can often lead to changes in GHG emissions in another sector.

Novel Technological and Management Options for Accelerating Transformational Changes in Rice and Livestock Systems

“…This result is not surprising as the higher tannin content in cassava leaves than in BH swards (Table 2) probably reduced the methanogen activity, as reported in previous studies [37]. Secondary compounds such as tannins have been reported to either target methanogen activity or disrupt the commensal relationship between methanogens and other microbes such as protozoa populations and fungi [26,38]. Thus tannins reduce gas production by reducing fiber digestion [39].…”

“…Therefore, as women are not generally recognized as decision-makers from the men's perspective, it is also probable that their needs and preferences may not be adequately considered when deciding on the adoption of CSA options. It is therefore possible that, without an understanding of these dynamics, adopted technological and management practices may increase the burden on women and thus increase their time poverty [26].…”

Invited review: Large-scale indirect measurements for enteric methane emissions in dairy cattle: A review of proxies and their potential for use in management and breeding decisions

“…Although this relationship holds in some studies (e.g., Chung et al, 2011;Van Zijderveld et al, 2010), treatment effects on CH 4 emissions and VFA proportions did not correspond in about half of the studies (e.g., Beauchemin et al, 2009;Brask et al, 2015;Supplementary Table S1; https://doi.org/10.3168/jds.2016-12030). Overall, the relations between CH 4 emission and both VFA and pH are variable in the literature and not as straightforward as expected from theory.…”

“…Although diet changes and feed additives can be effective mitigation strategies for CH 4 emissions (e.g., Beauchemin et al, 2009;Martin et al, 2010;Hristov et al, 2013b), their effects depend on continued use of the diet or additive and the rumen microbiome can adapt to additives. In contrast, breeding for reduced CH 4 emissions would have a permanent and cumulative effect (Wall et al, 2010).…”

Evaluation of greenhouse gas emissions from hog manure application in a Canadian cow–calf production system using whole-farm models

“…Various mitigation strategies have been proposed and implemented to minimise GHG from animal agriculture (Beauchemin et al 2009;Eckard et al 2010). However, often the strategies are applied to a single farm component (e.g.…”