Effect of the macroalgaeAsparagopsis taxiformison methane production and the rumen microbiome assemblage

Abstract

Background: Recent studies using batch-fermentation suggest that the red macroalgae Asparagopsis taxiformis might reduce methane (CH 4 ) emission 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 methane 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 producer 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 communities consistent with the Anna Karenina hypothesis, with increased beta-diversity, over time scales of approximately three 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 methane 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 in the largest milk producing state in the US. 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.

Effects of live feed manipulation with algal‐derived antimicrobial metabolites on fish larvae microbiome assembly: A molecular‐based assessment

“…One exquisite example of application of Asparagopsis spp. in regulating microbiome activities pertains to their use as a feed supplement (0.2-1.0% of the total organic matter) in livestock to modulate rumen fermentation and reduce methane production by over 80% (Kinley et al;Maia et al, 2016;Muñoz-Tamayo et al, 2020;Roque, Brooke, et al, 2019;. Although their validation as feed additives in other production systems is certainly encouraging, direct use of algal biomass to control diseases in fish larviculture must be considered with caution.…”

Comparative analysis of macroalgae supplementation on the rumen microbial community: Asparagopsis taxiformis inhibits major ruminal methanogenic, fibrolytic, and volatile fatty acid-producing microbes in vitro

“…The addition of certain seaweed species and their by-products to the diets of ruminant livestock has been extensively investigated and presents a promising and renewable approach to mitigate enteric CH 4 emissions (Abbott et al, 2020). Several species of red and brown macroalgae are known to inhibit microbial methanogenesis when included as a feed additive in the diet of ruminants (Machado et al, 2014(Machado et al, , 2016a(Machado et al, , 2018Roque et al, 2019). Among them, the bromoform containing red seaweed Asparagopsis taxiformis has been shown to have anti-methanogenic properties and can reduce CH 4 production by over 95% in vitro and in vivo (Machado et al, 2016b;Roque et al, 2019Roque et al, , 2021Terry et al, 2022).…”

Effects of nitrogen gas flushing in comparison with argon on rumen fermentation characteristics in in vitro studies

“…However, the studies identifying the effects of flushing gases on rumen fermentation are limited. Nitrogen gas (N 2 ) flushing is routinely used in rumen in vitro experiments [2][3][4]. It may affect rumen nitrogen metabolism as rumen microbes can utilize atmospheric N 2 [5][6][7] and thus may confound the obtained results.…”