Adelaide University researchers have demonstrated that a naturally derived seaweed compound can dramatically reduce methane emissions from beef cattle raised in extensive grazing systems, without harming calves.
The study, published in Frontiers in Animal Science, investigated the use of bromoform extract oil, derived from the red seaweed Asparagopsis, in pregnant and lactating Angus cows.
Methane is responsible for around 30 % of the rise in global temperatures since the industrial revolution, according to the International Energy Agency (IEA), and finding practical solutions for grazing systems – where animals roam freely and feed intake is less controlled – remains a significant challenge.
PhD student Kellie Wenham, from the School of Animal and Veterinary Sciences, said the results show strong potential for reducing emissions in real-world farming conditions.
“Across the eight-week trial involving 80 Angus cows, methane emissions were reduced by between 49 % and 77 % in cows receiving the supplement,” Ms Wenham said.
“This is a substantial reduction, particularly in an extensive system where delivering consistent supplementation can be difficult.”
The research found no negative effects on calf growth or development. Calves born to supplemented cows showed normal weight gain from birth through to 150 days of age, indicating no carry-over impacts from maternal supplementation.
“This is critical. In breeding systems, it’s not just about the cow – you need to be confident there are no unintended consequences for their offspring,” according to the corresponding author and supervisor, Dr Mariana Caetano.
The cows also maintained stable body weight throughout the trial, despite consuming slightly less feed with the bromoform supplement, suggesting potential cost savings for producers.
“In a commercial setting, reduced feed intake without a drop in productivity could translate into meaningful savings,” Dr Caetano said.
“That’s an important incentive for adopting bromoform, alongside the environmental benefits.”
While the results are promising, the study also identified some changes in blood chemistry in supplemented cows, leading to mild metabolic alkalosis in some animals.
“These changes were generally within acceptable ranges, but they highlight the need for further research into long-term health impacts and optimal dosing,” Dr Caetano said.
Some minor changes were also observed in calf blood markers, though these remained within normal physiological ranges.
Previous studies involving bromoform have largely focused on feedlot or intensive systems, where diet can be tightly controlled. This research is among the first to demonstrate strong methane reductions in breeding cows managed under grazing conditions.
“Our findings show that bromoform-based supplements can be effective beyond feedlots, including in pasture-based systems that dominate Australian beef production.”
The research team says further work is needed to refine delivery methods, optimize dosage, and better understand long-term impacts on animal health and productivity.
“There is real potential here, but adoption will depend on ensuring the approach is safe, practical and cost-effective for producers,” Ms Wenham said.
“If we can get that balance right, this could be a powerful tool to help the livestock industry reduce its environmental footprint.”
‘Efficacy of bromoform extract oil supplementation to mitigate methane emissions in Angus cows in an extensive system and the health impact on the cow-calf pair’ is published in Frontiers in Animal Science. DOI: 10.3389/fanim.2026.1789660