Methane Reduction Potential of Brown Seaweeds and Their Influence on Nutrient Degradation and Microbiota Composition in a Rumen Simulation Technique

Abstract

This study aimed to investigate the effects of two brown Icelandic seaweed samples (Ascophyllum nodosum and Fucus vesiculosus) on in vitro methane production, nutrient degradation, and microbiota composition. A total mixed ration (TMR) was incubated alone as control or together with each seaweed at two inclusion levels (2.5 and 5.0% on a dry matter basis) in a long-term rumen simulation technique (Rusitec) experiment. The incubation period lasted 14 days, with 7 days of adaptation and sampling. The methane concentration of total gas produced was decreased at the 5% inclusion level of A. nodosum and F. vesiculosus by 8.9 and 3.6%, respectively (P < 0.001). The total gas production was reduced by all seaweeds, with a greater reduction for the 5% seaweed inclusion level (P < 0.001). Feed nutrient degradation and the production of volatile fatty acids and ammonia in the effluent were also reduced, mostly with a bigger effect for the 5% inclusion level of both seaweeds, indicating a reduced overall fermentation (all P ≤ 0.001). Microbiota composition was analyzed by sequencing 16S rRNA amplicons from the rumen content of the donor cows, fermenter liquid and effluent at days 7 and 13, and feed residues at day 13. Relative abundances of the most abundant methanogens varied between the rumen fluid used for the start of incubation and the samples taken at day 7, as well as between days 7 and 13 in both fermenter liquid and effluent (P < 0.05). According to the differential abundance analysis with q2-ALDEx2, in effluent and fermenter liquid samples, archaeal and bacterial amplicon sequence variants were separated into two groups (P < 0.05). One was more abundant in samples taken from the treatment without seaweed supplementation, while the other one prevailed in seaweed supplemented treatments. This group also showed a dose-dependent response to seaweed inclusion, with a greater number of differentially abundant members between a 5% inclusion level and unsupplemented samples than between a 2.5% inclusion level and TMR. Although supplementation of both seaweeds at a 5% inclusion level decreased methane concentration in the total gas due to the high iodine content in the seaweeds tested, the application of practical feeding should be done 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

“…Chemical analysis of the seaweeds examined in this work indicated that only A. taxiformis contained measurable amounts of bromoform, explaining the negligible impact that the other two algae had on methanogenesis. Although P. mollis or M. japonica did not reduce methane levels, some seaweeds without anti-methanogenic activity have proven to be potent modulators of rumen microbiomes both in vivo ( Zhou et al, 2018 ) and in a RUSITEC system ( Belanche et al, 2016 ; Zhou et al, 2018 ; Künzel et al, 2022 ) due to the wide range of bioactives present in algae. To our knowledge M. japonica has not previously been evaluated for its effect on microbial communities, while P. mollis has been found to modify the composition of the gut microbial community in mice ( Mendez et al, 2020 ).…”

Evaluation of Different Brown Seaweeds as Feed and Feed Additives Regarding Rumen Fermentation and Methane Mitigation

“…There is some support for this theory in a recent study in which two species of brown seaweeds, A. nodosum and Fucus vesiculosus, were included with the basal diet at a level of 5%. Reductions in CH 4 by 8.9 and 3.6%, respectively, were associated with reductions in total gas production, IVDMD, and the production of VFA [48]. This could imply that the brown seaweeds tested in the current study might not have a direct effect on methanogenic archaea when compared with some other feed additives that are well known for their anti-methanogenic potential, such as A. taxiformis [49], 3-nitrooxypropanol (Bovaer ® ) [50], and a garlic-citrus extract (Mootral Ruminant ® ) [51].…”

Effect of Padina gymnospora biowaste inclusion on in vitro methane production, feed fermentation, and microbial diversity

“…In another study, a reduction of 17% in CH 4 (ml/g dig. OM) was reported on the incorporation of brown seaweed at 5.0% in the diet ( Künzel et al, 2022 ). The reduction in CH 4 production with the inclusion of BW was consistent with the previous reports, where brown seaweeds were used at the almost similar levels.…”