Dietary mitigation of enteric methane emissions and animal production from ruminants: Plant tannins mitigation options

Enteric methane (CH 4 ) emissions produced by microbial fermentation in the rumen provide the discharge of greenhouse gases (GHG) into the atmosphere. A reduction in ch 4 emissions would not only reduce GHG emissions but would also improve the efficiency of animal production. Methane is a source of energy loss from the animal which would otherwise be used for more efficient production of meat and milk. Animal dry matter intake (dmi) is the single important predictor of CH 4 production. Each 1.0 kg increase in dmi increased ch 4 production by an average of 20.53 (± 0.87) g per kg of dmi in beef and dairy cattle. However, total methanogens, total protozoa populations, and firmicutes: bacteroidetes (f: b) ratio can significantly affect this relationship. In addition, various dietary ch 4 interventions including ionophores, chemical compounds, legumes, essential oils, fats, saponins, probiotics, and plant secondary metabolites ( e.g. , tannins, saponins) have been investigated as methanogenesis inhibitors. However, in some cases, the desired anti-methanogenic effect may coexist with adverse effects such as decreasing dmi and feed efficiency. Tannins are thought to have both beneficial and detrimental effects on feed nutritive value and animal performance. One possible strategy to reduce GHG emissions is dietary modifications that include feeding tannin-rich diets to cattle and other ruminants. Properly designed tannin-rich diets can reduce GHG emissions as enteric CH 4 production without negative impacts on animal production. Therefore, GHG reduction strategies should be established to increase ruminant production efficiency, while minimizing losses of CH 4 and volatile organic compounds from animal agriculture.