Mitigation strategies to reduce enteric methane emissions from dairy cows: Update review

TLDR

Enteric methane is a major contributor to Canadian greenhouse gas emissions and represents a loss of feed energy, with existing mitigation strategies such as ionophores, fats, high‑quality forages, and increased grain use well researched, while new options—probiotics, acetogens, bacteriocins, archaeal viruses, organic acids, plant extracts, immunization, and genetic selection—show promise but require further validation and cost‑effectiveness assessment. This review updates current management practices and proposes new dietary strategies to reduce methane emissions from dairy cows. The strategies work by altering ruminal fermentation, directly inhibiting methanogens and protozoa, diverting hydrogen away from methanogenesis, and employing additives such as probiotics, acetogens, bacteriocins, archaeal viruses, organic acids, plant extracts, immunization, and genetic selection. Keywords: Enteric methane, dairy cattle, mitigation.

Abstract

Enteric methane (CH 4 ) emission is a major contributor to Canadian greenhouse gas emissions, and also a loss of feed energy during production. The objective of this paper is to provide an update on current management practices and new dietary strategies recently proposed to reduce CH 4 emissions from ruminants. Existing mitigation strategies for dairy, e.g., the addition of ionophores, fats, use of high-quality forages, and increased use of grains, have been well researched and applied. These nutritional changes reduce CH 4 emissions by manipulating ruminal fermentation, directly inhibiting methanogens and protozoa, or by diverting hydrogen ions away from methanogens. Current literature has identified new CH 4 mitigation options. These include the addition of probiotics, acetogens, bacteriocins, archaeal viruses, organic acids, plant extracts (e.g., essential oils) to the diet, as well as immunization, and genetic selection of cows. These new strategies are promising, but more research is needed to validate these approaches and to assess in vivo their effectiveness in reducing CH 4 production by dairy cows. It is also important to evaluate CH 4 mitigation strategies in terms of the total greenhouse gas budget and to consider the cost associated with the various strategies. More basic understanding of the natural differences in digestion efficiencies among animals as well as a better knowledge of methanogens and their interaction with other organisms in the rumen would enable us to exploit the potential of some of the new CH 4 mitigation strategies for dairy cattle production. Key words: Enteric methane, dairy cattle, mitigation