Opportunities for biological control of ruminal methanogenesis

Methane is a major waste product from ruminants, contributing 53% of Australia's total emissions of the gas. A range of chemical inhibitors of methanogenesis are known to be effective but the real and perceived risks to the environment and health from chemical residues may curtail widespread application of these products in ruminant industries. As with other agricultural industries, future control of unwanted organisms (such as methanogens) is likely to lie with biocontrol agents rather than with chemicals. Opportunities exist for biological reduction of rumen methane emissions using direct means (viruses and bacteriocins specific to methanogens), and indirectly through the elimination of rumen protozoa which symbiotically support some rumen methanogens. The feasibility of these approaches and their current research position are discussed. The most promising work to date is using the common food preservative, nisin (a safe and naturally occurring bacteriocin). When ruminal contents were incubated with nisin in vitro, methane emissions were reduced by 36%.