Advanced estimation and mitigation strategies: a cumulative approach to enteric methane abatement from ruminants

Abstract

Methane, one of the important greenhouse gas, has a higher global warming potential than that of carbon dioxide. Agriculture, especially livestock, is considered as the biggest sector in producing anthropogenic methane. Among livestock, ruminants are the highest emitters of enteric methane. Methanogenesis, a continuous process in the rumen, carried out by archaea either with a hydrogenotrophic pathway that converts hydrogen and carbon dioxide to methane or with methylotrophic pathway, which the substrate for methanogenesis is methyl groups. For accurate estimation of methane from ruminants, three methods have been successfully used in various experiments under different environmental conditions such as respiration chamber, sulfur hexafluoride tracer technique, and the automated head-chamber or GreenFeed system. Methane production and emission from ruminants are increasing day by day with an increase of ruminants which help to meet up the nutrient demands of the increasing human population throughout the world. Several mitigation strategies have been taken separately for methane abatement from ruminant productions such as animal intervention, diet selection, dietary feed additives, probiotics, defaunation, supplementation of fats, oils, organic acids, plant secondary metabolites, etc. However, sustainable mitigation strategies are not established yet. A cumulative approach of accurate enteric methane measurement and existing mitigation strategies with more focusing on the biological reduction of methane emission by direct-fed microbials could be the sustainable methane mitigation approaches.

Keywords: Accurate methane estimation; Direct-fed microbials; Methane mitigating approach.

Fig. 1.. Pictorial presentation of widely used enteric methane measurement techniques.

(A) Respiration chambers (RC), (B) Sulfur hexafluoride (SF₆) tracer technique, (C) Automated head-chamber system (AHCS), (D) Methane hood (MH) system [47,69,73].

Fig. 2.. A schematic presentation of the possible targets to reduce CH₄ emissions from ruminants.

The boxes without dark shade could be the targets for CH₄ mitigation and boxes with dark shade are the options that have been studied either in vitro or in vivo to reduce CH₄ production [52,109,116,123,126,131].