Resumen
- There is irrefutable evidence that human activities are affecting the global climate through the production of Green House Gases (GHG) of which methane (CH4) has a high warming potential. Enteric fermentation and manure from ruminants represent about 30 to 40% of the total anthropogenic CH4 emissions. This paper summarizes existing technologies to reduce enteric CH4emissions in ruminants given emphasis to dietary and rumen manipulation, animal selection/ breeding and improvement of production systems. Differences in enteric CH4production among animal species based on anatomy of the GI tract, digestive physiology, rumen fermentation and grazing habits are also discussed. Inhibition of enteric CH4emission is possible through the use of ionophores, organic acids and oils. Feeding plants containing secondary metabolites (i.e. tannins and saponins) can reduce CH4production. Breeding for improved feed conversion efficiency (lower residual feed intake) is likely to reduce total and per unit product CH4emissions. Results using the IPCC Tier II model predict that goats and high producing dairy cattle can potentially produce less CH4emissions per unit of milk than Cebu cattle or sheep, while small ruminants (goats and sheep) produce less CH4per unit of live weight gain (meat) than cattle. The introduction of improved high quality forages and the implementation of efficient pasture utilization practices (grazing system and stocking rate) can result in most cases in improved animal production and in increased absolute CH4emissions, but in reduced CH4 per unit of animal product.