Methane reduction, health and regulatory considerations regarding Asparagopsis and bromoform for ruminants

Abstract

Asparagopsis (A. taxiformis and A. armata) as a dry feed additive, and novel oil-based formulations containing bromoform are effective at reducing enteric methane emissions in ruminant livestock. An inclusion rate of Asparagopsis at 0.2%–0.5% of the daily diet for cattle of say 470 kg consuming 15 kg dry matter (DM) per day is equivalent to 30–75 g/day Asparagopsis delivering 180–450 mg/day bromoform (at 6 mg bromoform per gram of seaweed) per animal equivalent to 0.4–1.0 mg/kg/day of bromoform. This is a low dose when compared to those evaluated in animal toxicity studies. A response relationship in terms of emission reductions and the dosage of bromoform ingested, is established, as opposed to dose responses linked to seaweed biomass. Most of the research studies on bromoform as a methane mitigant have used Asparagopsis. Nevertheless, the primary interest from a regulatory perspective is bromoform, the most prevalent bioactive. Regulatory considerations to enable safe use of bromoform for methane mitigation in ruminants are described. A key conclusion is that bromoform, administered in very low doses, is not bioavailable at measurable levels. Hence the risk of residue transfer or toxicity in livestock and humans will be minimal.