NEW PERSPECTIVES ON REDUCING METHANE EMISSIONS FROM BEEF AND DAIRY CATTLE PRODUCTION

摘要

Ruminants are a source of greenhouse gases (GHGs), primarily due to enteric methane (CHU) production from ruminai fermentation of feed. Archeal methanogens within the rumen play an important role in feed digestion by preventing hydrogen accumulation through the reduction of CO2 to CHU. Although CHU production is necessary for efficient digestion, it represents an energetic loss of up to 12% of the gross energy intake of the animal. There is a global effort to develop strategies that mitigate entericCHU production from ruminants. Improved diet formulation, herd health, management and animal selection can increase milk and meat output, or improve production efficiency, both which reduce emissions relative to the quantity of meat/milk produced on thefarm. Other approaches that may directly reduce methanogenesis in the rumen include: dietary inclusion of fat supplements, increased starch content of diets, inhibitors that block formation of ChU in the rumen (3-nitrooxypropanol), alternative hydrogen sinks (nitrate), biologically active plant compounds (condensed tannins, saponins, and essential oils), and rumen fermentation modifiers (bacterial and fungal direct-fed microbials). The optimum strategy will depend on the particular farm, its geographiclocation, the feedstuffs available, and type of animals fed. This review provides a critical evaluation of the various CH_4 mitigation options available, or soon to be available, to livestock producers. Potential mitigation practices must be assessed using a life cycle approach to ensure reductions in CH_4 do not give rise to GHGs elsewhere in the farming system. Ultimately, the goal is to reduce GHGs per kilogram of meat or milk produced.