Enteric methane emissions in grazing dairy systems

Summary: Quantifying and mitigating enteric CH4 from pastoral dairy systems is challenging. A variety of dietary- and husbandry-management strategies are being evaluated to mitigate enteric CH4 emissions in dairy cattle. Some strategies may not be applicable to pastoral dairy systems. Further research is needed to identify protracted strategies for reducing CH4 emissions that do not require frequent vaccination or constant feeding, particularly for grazed herds that do not receive supplementation. Breeding animals for reduced CH4 emissions shows promise, as long as the purchase of such animals is not cost-prohibitive and animal production is not impaired. More robust data sets are needed to develop life cycle assessments that account for all inputs and outputs on the farm that affect carbon and nitrogen cycling.