Enteric Methane Mitigation

Enteric methane production contributes to most of the greenhouse gas (GHG) emissions from livestock; therefore, it is key to mitigating such emissions. A number of strategies have been developed to reduce enteric methane emissions. These vary from those that directly target methanogensis to indirectly reducing emissions by improving feed efficiency. Recent advances in understanding of the rumen and methanogenesis has led to development of feed additives that have the potential to reduce enteric methane emissions substantially. Feed additives work by either inhibiting methanogenesis or modifying the rumen environment, such that methane production is reduced. Feed additives that inhibit methanogenesis or compete with substrate for methanogens include 3-nitroxypropanol (3NOP), nitrates, and halogenated compounds containing organisms such as macroalgae. Rumen modifiers do not act directly on methanogens but rather on the conditions that promote methanogenesis. These feed additives include lipids, plant secondary compounds and essential oils. The efficacy of lipids has been studied extensively, and although supplementation with medium chain and polyunsaturated fatty acids has shown substantial reduction in enteric methane production, the results have been variable. Similarly, secondary plant compounds and essential oils have shown inconsistent results, ranging from substantial reduction to modest increase in enteric methane emissions. Due to continued interest in this area, research is expected to accelerate in developing feed additives that can provide options in mitigating enteric methane emissions. Increased animal production efficiency or improved reproduction would also indirectly reduce methane emissions as it reduces methane intensity (methane produced per unit of product). Improved efficiency could be achieved through better forages (such as high sugar/starch or low fiber) or better management particularly in grazing systems. Breeding for low methane emissions has also shown a promise in selecting breeds for reduced enteric methane emissions