Enteric methane mitigation technologies for ruminant livestock: a synthesis of current research and future directions

Abstract

Enteric methane (CH(4)) emission in ruminants, which is produced via fermentation of feeds in the rumen and lower digestive tract by methanogenic archaea, represents a loss of 2% to 12% of gross energy of feeds and contributes to global greenhouse effects. Globally, about 80 million tonnes of CH(4) is produced annually from enteric fermentation mainly from ruminants. Therefore, CH(4) mitigation strategies in ruminants have focused to obtain economic as well as environmental benefits. Some mitigation options such as chemical inhibitors, defaunation, and ionophores inhibit methanogenesis directly or indirectly in the rumen, but they have not confirmed consistent effects for practical use. A variety of nutritional amendments such as increasing the amount of grains, inclusion of some leguminous forages containing condensed tannins and ionophore compounds in diets, supplementation of low-quality roughages with protein and readily fermentable carbohydrates, and addition of fats show promise for CH(4) mitigation. These nutritional amendments also increase the efficiency of feed utilization and, therefore, are most likely to be adopted by farmers. Several new potential technologies such as use of plant secondary metabolites, probiotics and propionate enhancers, stimulation of acetogens, immunization, CH(4) oxidation by methylotrophs, and genetic selection of low CH(4)-producing animals have emerged to decrease CH(4) production, but these require extensive research before they can be recommended to livestock producers. The use of bacteriocins, bacteriophages, and development of recombinant vaccines targeting archaeal-specific genes and cell surface proteins may be areas worthy of investigation for CH(4) mitigation as well. A combination of different CH(4) mitigation strategies should be adopted in farm levels to substantially decrease methane emission from ruminants. Evidently, comprehensive research is needed to explore proven and reliable CH(4) mitigation technologies that would be practically feasible and economically viable while improving ruminant production.

Evaluation of feeds from tropical origin for in vitro methane production potential and rumen fermentation in vitro

“…A number of dietary and management mitigation options and policies have been advocated to lowering methane production from livestock production systems (Patra, 2012b;Hristov et al, 2013). However, all these mitigation strategies may not be appropriate for all feeding situations, particularly in developing tropical countries, where livestock production systems are low-input-output enterprises and farmers could not adopt expensive technologies of methane mitigation like other nutritional technologies (Owen et al, 2012).…”

Current available strategies to mitigate greenhouse gas emissions in livestock systems: an animal welfare perspective

“…A higher risk of cancer was also described after longterm chloroform exposure in humans (Reitz et al, 1990). The risk of toxicity using supplementation of halomethanes to reduce CH 4 emissions in ruminants has been reported by Patra (2012) with effects ranging from liver damage to death after a long period of diet supplementation. Considering all the detrimental side effects of halogenated compounds, it is very unlikely that they could be used as routine supplements for CH 4 mitigation.…”

Good science for improving policy: greenhouse gas emissions from agricultural manures

“…They comment that rumen manipulation technologies require much more research as vaccine use is controversial and enzymes have yet to show any sustained positive results. Patra (2012) remarked that most enteric mitigation strategies have not been tested in long-term experiments and, thus, require extensive future research. Although the magnitude of the costs associated with enteric mitigation technologies is not yet known, it is likely that they will be significant.…”