Red Seaweed Supplement Cuts Methane Emissions by Seventy-Seven Percent in Free-Roaming Grazing Cattle

New study shows red seaweed supplements can slash methane emissions in grazing beef herds by up to 77% while improving feed efficiency.

By: AXL Media

Published: Apr 28, 2026, 6:42 AM EDT

Source: Information for this report was sourced from Earth.com

Targeting Agriculture’s Hidden Climate Driver

Livestock methane emissions represent one of the most persistent challenges in global climate policy, accounting for approximately 30% of temperature rise since the industrial revolution. While the issue is well-documented, finding a solution that works for free-roaming grazing cattle—which represent the vast majority of the beef industry—has proven difficult. Unlike cattle in controlled feedlots, grazing animals eat freely across expansive landscapes, making it nearly impossible for farmers to manage their dietary intake. However, new research suggests that a specific red seaweed variety may provide the breakthrough necessary to decarbonize traditional pasture-based farming.

The Molecular Power of Asparagopsis Seaweed

The secret to this dramatic emission reduction lies in a natural compound called bromoform, found in the red seaweed Asparagopsis. When ingested, bromoform interferes with the specific digestive enzymes in a cow's rumen that produce methane gas as a byproduct of grass fermentation. Led by PhD student Kellie Wenham and Dr. Mariana Caetano, the University of Adelaide team tested a bromoform extract oil supplement on a herd of 80 pregnant and lactating Angus cows. The results were immediate and substantial, with methane emissions falling between 49% and 77% across the treated group.

Ensuring the Health of the Next Generation

In any breeding operation, the primary concern for producers is the health and development of the offspring. The researchers tracked the calves born to the supplemented cows for 150 days to ensure that the maternal diet did not cause unintended developmental delays. Data showed that the calves grew at normal rates and maintained healthy weight gain, providing essential reassurance for the livestock industry. Dr. Caetano emphasized that for these supplements to be commercially viable, farmers must be confident that environmental benefits do not come at the expense of the herd’s future productivity.