Effect of the macroalgae Asparagopsis taxiformis on methane production and rumen microbiome assemblage

Abstract

Background: Recent studies using batch-fermentation suggest that the red macroalgae Asparagopsis taxiformis has the potential to reduce methane (CH 4) production from beef cattle by up to~99% when added to Rhodes grass hay; a common feed in the Australian beef industry. These experiments have shown significant reductions in CH 4 without compromising other fermentation parameters (i.e. volatile fatty acid production) with A. taxiformis organic matter (OM) inclusion rates of up to 5%. In the study presented here, A. taxiformis was evaluated for its ability to reduce methane production from dairy cattle fed a mixed ration widely utilized in California, the largest milk producing state in the US. Results: Fermentation in a semi-continuous in-vitro rumen system suggests that A. taxiformis can reduce methane production from enteric fermentation in dairy cattle by 95% when added at a 5% OM inclusion rate without any obvious negative impacts on volatile fatty acid production. High-throughput 16S ribosomal RNA (rRNA) gene amplicon sequencing showed that seaweed amendment effects rumen microbiome consistent with the Anna Karenina hypothesis, with increased β-diversity, over time scales of approximately 3 days. The relative abundance of methanogens in the fermentation vessels amended with A. taxiformis decreased significantly compared to control vessels, but this reduction in methanogen abundance was only significant when averaged over the course of the experiment. Alternatively, significant reductions of CH 4 in the A. taxiformis amended vessels was measured in the early stages of the experiment. This suggests that A. taxiformis has an immediate effect on the metabolic functionality of rumen methanogens whereas its impact on microbiome assemblage, specifically methanogen abundance, is delayed. Conclusions: The methane reducing effect of A. taxiformis during rumen fermentation makes this macroalgae a promising candidate as a biotic methane mitigation strategy for dairy cattle. But its effect in-vivo (i.e. in dairy cattle) remains to be investigated in animal trials. Furthermore, to obtain a holistic understanding of the biochemistry responsible for the significant reduction of methane, gene expression profiles of the rumen microbiome and the host animal are warranted.

Blue Growth Potential to Mitigate Climate Change through Seaweed Offsetting

“…Expanding other markets-such as the use of certain seaweed strains in livestock feed, where inclusion in cow diets Hypoxia is considered dissolved oxygen levels less than 2 mgL À1 . Acidification is represented here by estimated aragonite saturation (U) less than 3.0. may significantly (75%-99%) reduce ruminant methane production [48][49][50]-as well as offshore production for biofuel [16], could further accelerate economies of scale. That said, climate change and increases in CO 2 will challenge some farmed seaweed species' growth and survival [3,14], limiting the upper bounds of sequestration while potentially promoting growth in others [51,52].…”

Influence of Seaweed Supplements on the Intestinal Bacteria in the Rabbitfish Siganus Fuscescens: Evidence for a Core Microbiome

“…Feeding ruminants the red seaweed Asparagopsis taxiformis quickly (e.g. 3 days) changed the rumen microbial composition leading to drastic reduction of methanogenic Archaea and as a result led to reductions in enteric methane emissions [67,68]. This was the result of supplementing the diets of the ruminants (ovine and bovine) with up to 5% A. taxiformis which produces and accumulates halogenated compounds including the anti-methanogenic bromoform [69].…”

Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

“…Achievable methods for CH 4 emission reductions have already been identified in a variety of sectors, some of them more developed and others still in the research stage. Within agriculture, preliminary research has shown how red algae and other dietary supplements can reduce methane emissions from cattle and sheep by as much as 95% (e.g., Li et al, ; Roque et al, ). Considerably more work is needed, however, to determine whether such supplements can be scaled industrywide and to confirm no change to nutrition or taste.…”