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PLoS ONESystems BiologyPeer-reviewed journal article

Red seaweed (Asparagopsis taxiformis) supplementation reduces enteric methane by over 80 percent in beef steers

Breanna Michell RoqueiD, Marielena Venegas, Robert D. Kinley, Rocky de NysiD, T. L. Neoh, T.L. Duarte, Xiang YangiD, Joan King Salwen, Ermias KebreabiD

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Abstract

The red macroalgae (seaweed) Asparagopsis spp. has shown to reduce ruminant enteric methane (CH4) production up to 99% in vitro. The objective of this study was to determine the effect of Asparagopsis taxiformis on CH4 production (g/day per animal), CH4 yield (g CH4/kg dry matter intake (DMI)), average daily gain (ADG), feed conversion efficiency (FCE), and carcass and meat quality in growing beef steers. Twenty-one Angus-Hereford beef steers were randomly allocated to one of three treatment groups: 0% (Control), 0.25% (Low Dose; LD), and 0.5% (High Dose; HD) A. taxiformis inclusion based on organic matter intake. Steers were fed 3 diets: high, medium, and low forage total mixed ration (TMR) representing typical life-stage diets of growing beef steers. The LD and HD treatments over 147 days reduced enteric CH4 yield 45 and 68%, respectively; however, there was an interaction between TMR type and the magnitude of CH4 yield reduction. Supplementing the low forage TMR reduced CH4 yield 69.8% (P <0.001) for LD and 80% (P <0.001) for HD treatment. Hydrogen (H2) yield (g H2/DMI) increased significantly (P<0.001) 336 and 590% compared to Control for the LD and HD treatments, respectively. No differences were found in carbon dioxide (CO2) yield (g CO2/DMI), ADG, carcass quality, strip loin proximate analysis and shear force, or consumer taste preferences. DMI tended (P = 0.08) to decrease 8% in steers in LD treatment but significantly (P = 0.002) reduced 14% in steers in HD treatment. Conversely, FCE tended to increase 7% in steers in LD treatment (P = 0.06) and increased 14% in steers in HD (P < 0.01) treatment compared to Control. The persistent reduction of CH4 by A. taxiformis supplementation suggests that this is a viable feed additive to significantly decrease the carbon footprint of ruminant livestock and potentially increase production efficiency.

In-depth summary

Claude Opus 5.5 · xhigh effort · 5 Nov 2026 · from the full text of version 1 (16 Jul 2020)

Supplementing beef steer diets with 0.25% or 0.5% Asparagopsis taxiformis for 147 days reduces enteric methane yield by up to 80% and improves feed efficiency without altering meat quality.

Enteric fermentation in ruminant livestock is a major source of anthropogenic methane and a dietary energy loss of up to 11%, yet many anti-methanogenic feed additives lose efficacy or lack long-term testing across life-stage diets. This 147-day trial shows persistent methane reduction and improved feed efficiency in beef steers fed red seaweed across starter, transition, and finisher diets without harming meat quality or safety.

Key results

  1. ShownDietary Asparagopsis taxiformis supplementation persistently reduced enteric methane production and yield across the 147-day feeding period.

    Over 21 weeks, 0.25% (Low Dose, LD) and 0.5% (High Dose, HD) organic matter inclusion of A. taxiformis (7.8 mg bromoform/g dry weight) reduced daily enteric methane production by 50.6% and 74.9% and methane yield (g CH4/kg dry matter intake) by 45% and 68%, respectively, compared to Control (P < 0.01). · Abstract; 2.1 Study design, animals, and diets; 3.1 Gas parameters; 4.1 Enteric methane production and yield

  2. ShownMethane mitigation efficacy increased as dietary neutral detergent fiber (NDF) decreased across life-stage total mixed rations.

    Methane production reductions negatively correlated with dietary NDF (r^2 = 0.89 across 33.1% high-, 25.8% medium-, and 18.6% low-forage diets), with methane yield decreasing by 32.7%, 44.6%, and 69.8% in LD and by 51.9%, 79.7%, and 80.0% in HD across high-, medium-, and low-forage diets, respectively (P < 0.01; P < 0.001 in low-forage). · Abstract; 3.1 Gas parameters; 4.1 Enteric methane production and yield

  3. ShownSeaweed supplementation increased enteric hydrogen emissions without significantly altering total daily carbon dioxide production.

    Collective hydrogen production increased by 318% (LD) and 497% (HD) and hydrogen yield (g H2/kg DMI) increased by 336% (LD) and 590% (HD) compared to Control (P < 0.001), whereas daily CO2 production was unaffected (though CO2 yield per kg DMI was higher in HD, P = 0.03). · Abstract; 3.1 Gas parameters

  4. ShownHigh-dose seaweed inclusion reduced dry matter intake while maintaining average daily weight gain, significantly increasing feed conversion efficiency.

    Across all feeding stages, dry matter intake tended to decrease by 8% in LD (P = 0.08) and decreased by 14% in HD (P = 0.002), while average daily gain (~1.56 kg/day) did not differ, resulting in a 7% trend (P = 0.06) and a 14% significant increase (P < 0.01) in feed conversion efficiency (ADG/DMI) for LD and HD, with average cost per kg gain differentials of -$0.18 USD (LD) and -$0.37 USD (HD). · Abstract; 3.2 Animal production parameters; 4.3 Animal production parameters

  5. ShownSupplementation left no detectable bromoform residues, kept meat iodine levels well within human safety limits, and did not affect carcass traits or consumer sensory ratings.

    Bromoform was below detection (0.06 mg/kg) in all strip loin and liver samples; strip loin iodine averaged 0.08 ug/g in LD and 0.15 ug/g in HD (P < 0.01 vs Control <0.10 mg/g), well below human upper limits (200-1,100 ug/day); and Warner-Bratzler shear force (2.81, 2.66, 2.61 kg), slice shear force (17.1, 16.75, 17.4 kg), proximate composition, and 112-person taste panel scores did not differ (P > 0.05). · 2.2 Sample collection and analysis; 3.3 Carcass quality parameters; 4.4 Bromoform and iodine residues

Methods, data and reproducibility

Twenty-one Angus-Hereford steers were randomized to 0% (Control), 0.25% (Low Dose), or 0.5% (High Dose) freeze-dried Asparagopsis taxiformis supplementation (organic matter basis) for 147 days across sequential 63-day high-, 21-day medium-, and 63-day low-forage rations. Enteric CH4, H2, and CO2 were sampled every 3 weeks via GreenFeed, and carcasses were tested by GC/MS, shear force, and a 112-person sensory panel.

  • Angus-Hereford cross beef steers fed 0%, 0.25%, or 0.5% Asparagopsis taxiformis over 147 days across high, medium, and low forage diets · beef steers (Bos taurus) and Asparagopsis taxiformis · n = 21 steers enrolled (20 analyzed after 1 HD steer was excluded due to injury)
  • Consumer sensory evaluation panel rating strip loin steak tenderness, flavor, juiciness, and overall acceptance · human · n = 112 participants across 5 sessions
Methods & tools
GreenFeed system, Shimadzu QP2010 Ultra GC/MS, TMS Pro Texture Analyzer, R, lme (linear mixed-effects models)
Reagents & environment
R statistical software (version 3.6.1)
Reproducibility gaps
Raw animal performance, gas emission logs, sensory panel datasets, and R analysis scripts are not linked to an external repository in the text.
Limitations (2)
  • The number of animals per treatment group was small (20 steers completed the trial across three groups after one HD steer was injured), which limited statistical power to detect significant differences in cost per kg of weight gain. · stated by the authors
  • Seaweed was only tested at low dietary inclusion rates (0.25% and 0.5% of organic matter), which may explain the lack of objective meat tenderness changes reported with higher macro- or microalgae inclusion rates in other studies. · stated by the authors

Read this if you study enteric methane mitigation, ruminant nutrition, or sustainable livestock production and want long-term in vivo efficacy, feed-efficiency, and meat-safety data for Asparagopsis taxiformis.

Citations
432
FWCI
78.71
Field percentile
top 1%

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