Recent Advances in Measurement and Dietary Mitigation of Enteric Methane Emissions in Ruminants

Methane (CH(4)) emission, which is mainly produced during normal fermentation of feeds by the rumen microorganisms, represents a major contributor to the greenhouse gas (GHG) emissions. Several enteric CH(4) mitigation technologies have been explored recently. A number of new techniques have also been developed and existing techniques have been improved in order to evaluate CH(4) mitigation technologies and prepare an inventory of GHG emissions precisely. The aim of this review is to discuss different CH(4) measuring and mitigation technologies, which have been recently developed. Respiration chamber technique is still considered as a gold standard technique due to its greater precision and reproducibility in CH(4) measurements. With the adoption of recent recommendations for improving the technique, the SF(6) method can be used with a high level of precision similar to the chamber technique. Short-term measurement techniques of CH(4) measurements generally invite considerable within- and between-animal variations. Among the short-term measuring techniques, Greenfeed and methane hood systems are likely more suitable for evaluation of CH(4) mitigation studies, if measurements could be obtained at different times of the day relative to the diurnal cycle of the CH(4) production. Carbon dioxide and CH(4) ratio, sniffer, and other short-term breath analysis techniques are more suitable for on farm screening of large number of animals to generate the data of low CH(4)-producing animals for genetic selection purposes. Different indirect measuring techniques are also investigated in recent years. Several new dietary CH(4) mitigation technologies have been explored, but only a few of them are practical and cost-effective. Future research should be directed toward both the medium- and long-term mitigation strategies, which could be utilized on farms to accomplish substantial reductions of CH(4) emissions and to profitably reduce carbon footprint of livestock production systems. This review presents recent developments and critical analysis on different measurements and dietary mitigation of enteric CH(4) emissions technologies.