Macroalgae as feed supplement for reduction of methane emission in livestock : Overview of current knowledge and potential Nordic species

Abstract: Climate change is a fact and production systems are in need of modernization and sustainable development. Methane is a problematic and potent greenhouse gas and is emitted as a natural byproduct from livestock metabolism. Asparagopsis taxiformis is an exotic alga that has been found to reduce methane production in livestock rumen by 99% when ingested with everyday feed, at as low inclusion rates as 2% of total organic matter. The biochemical mechanism behind the methane emission reduction is an inhibition of methanogens in the final enzymatic step of methanogenesis in the rumen. This inhibition is conducted by algae secondary metabolites, especially bromoform. Algae species found in Swedish watercourses are plenty, however only few species contain the desired secondary metabolites of interest. Red algae seem to be the most potent producers of antimethanogenic secondary metabolites. These algae can potentially be produced in open or closed systems and thus be used as supplements in livestock feed for methane reduction. However, the possibility for sustainable largescale algae production and effects on animal health has to be investigated properly before algae can be used commercially. A possible future product has to be accepted by the farmers and be easily integrated with the basal feed. The market in Sweden has few actors that work with algae. Because of this there is need of further research and development of this sector. Nevertheless, this can mean the rise of a potential new niche on the countryside.