Validating Antimethanogenic Properties of Red Macro Algae for Provisional Patent

Summary

In Australia, agriculture is regarded as one of the major contributors to greenhouse gas emissions, accounting for 16% of total emissions from all sectors. Enteric fermentation from ruminant livestock contributes a large proportion of these emissions as methane.

Diet manipulation is generally regarded as an effective approach in which the ruminant livestock sector could reduce enteric contributions to Australia's GHG emissions. A number of feed additives have previously been described with potential to reduce enteric methane production, but few are persistent over time and most have a negative impact on intake and/or digestibility when fed in quantities that result in a mitigation response. The use of macroalgae as a feed additive to support animal productivity and thereby reduce emission intensity has been investigated. The inclusion of algae biomass in vitro has been described and forms the basis of an international patent for the use of a red macroalga to reduce enteric methanogenesis in ruminants with International Publication Number WO 2015/109362 A2.

This project has now determined the effect of supplementing a pelleted grain diet with a marine red macroalga on enteric methane production and rumen function. The overall objective was to provide a sufficient data set to support claims based on previous in vitro trials and a short term in vivo trial using Brahman steers. The effectiveness of accumulated bioactives in Asparagopsis biomass on reducing rumen methanogenesis was assessed across five inclusion rates compared to a control (no alga) using sheep as the experimental animal. The potential of including Asparagopsis taxiformis in the diet to mitigate methane production has now been described and clearly demonstrates the antimethanogenic potential of naturally occurring algal bioactives in vivo.

Twenty four merino cross wethers were allocated to one of five groups based on the daily inclusion rate of Asparagopsis [0 (control), 0.5, 1.0, 2.0, 3.0 % on an organic matter basis]; equivalent to 0, 13, 26, 58 and 80 g/d algae as fed, respectively. Individual feed intake was measured over 75 d, rumen fluid and blood samples were collected to determine the effect of Asparagopsis on rumen fermentation and animal health, respectively. Individual animal methane production was measured on three occasions using open-circuit respiration chambers.