2 Dec 2024

Pelleted Asparagopsis seaweed cut methane 37.7% on average in grazing steers

Climate and environmentFood and agriculture
AI illustration · Illustrative scene, not a photograph of the specific device or experiment.

What was demonstrated

In a 70-day trial with 24 Wagyu-Angus crossbred steers on irrigated pasture at a ranch in Montana, steers given pelleted Asparagopsis taxiformis (Brominata) at 20% of pellet composition had an average enteric methane reduction of 37.7% compared with controls, as stated in the paper. Methane was measured with GreenFeed units, which also dispensed the pellets. The abstract reports 115 vs 185 g/d of enteric methane in the optimal and decreasing phases. Average bromoform intake was 193 mg/d. Liveweight, average daily gain and predicted dry matter intake did not differ between groups. Pasture supplied more than 95% of total feed intake.

Why it matters

The introduction notes that earlier antimethanogenic studies were mostly run under controlled conditions with daily supplementation. This trial tested a pelleted supplement in grazing cattle, with the pellets dispensed through GreenFeed units. The result suggests the approach may be workable in grazing systems, but it comes from one small trial and does not show effects at herd or farm scale.

Caveats

  • This was one trial with 24 steers over 70 days on a single ranch. The sample was small (figure captions list n = 9 per mean, and the paper does not state how many steers were excluded for atypical weight changes), so it is not a herd or farm-scale result.
  • Methane was measured with GreenFeed units. The authors say these reliably detect relative differences, but the absolute values may be less accurate.
  • Dry matter intake was predicted rather than measured, and the authors flag a potential risk of a Type II error because of limited sample size and variability in those intake estimates. Bromoform intake fell later in the trial, which the authors attribute to palatability.
  • One author is a scientific adviser to Blue Ocean Barns, and the research was partly supported by Matador Ranch. The control and treatment pellets also differed in ingredients.

Technology profiles

Sources

  1. peer reviewed paper
    Mitigating methane emissions in grazing beef cattle with a seaweed-based feed additive: Implications for climate-smart agriculture
    Paulo Meo-Filho, John F Ramirez-Agudelo, Ermias Kebreab. Proceedings of the National Academy of Sciences of the United States of America, 2 Dec 2024. DOI: 10.1073/pnas.2410863121.

Last reviewed 21 Oct 2026.