A research team at the University of California Agriculture and Natural Resources (UC ANR) is examining whether red seaweed can be a practical additive to reduce methane emissions from cattle grazing on California rangelands. Previous studies have shown that including red seaweed (Asparagopsis taxiformis) in cattle diets can cut methane production by up to 90%, but these results were obtained in controlled environments rather than open pastures.
“The challenge now is finding a reliable method of delivering the seaweed product to cattle grazing on pasture,” said Andrea Warner, University of California Cooperative Extension livestock and natural resources advisor for Sutter, Yuba, Placer, and Nevada counties.
Warner explained that unlike feedlots or dairies where animals are fed daily in controlled settings, cattle on rangelands may graze across hundreds of acres. In an earlier attempt to address this challenge, researchers mixed red seaweed into salt-based mineral supplements placed in “free choice” feeders. However, they found inconsistent supplement consumption among the cattle and limited ability to measure actual methane reductions.
“Our results really said that we needed better capabilities to make measurements,” said Sheila Barry, UCCE livestock and natural resources advisor for the San Francisco Bay Area.
Barry was lead author of a study funded by the Russell L. Rustici Rangeland and Cattle Research Endowment at UC Davis. The study concluded that more research with improved methods was necessary to determine how seaweed additives could be effectively used on rangelands.
The new project, located at UC ANR’s Sierra Foothill Research and Extension Center in Browns Valley, Yuba County, aims to address these limitations. It is funded by the California Department of Food and Agriculture’s Livestock Enteric Methane Emission Reduction Research Program. The initial phase involves palatability trials to see if adding seaweed affects cows’ intake of mineral supplements. Later phases will evaluate consistency in consumption, confirm any methane reductions, and assess impacts on animal performance such as weight changes.
Methane from ruminant livestock represents about 6% of global human-related greenhouse gas emissions. Reducing methane from cattle is considered a key strategy for near-term climate change mitigation because methane is a short-lived greenhouse gas.
“Given that it’s a short-lived greenhouse gas, there’s an opportunity – if we can reduce the amount of methane that’s coming from ruminants – to contribute more quickly to reducing greenhouse gases in the atmosphere,” Barry said.
California’s 34 million acres of rangeland support most of its beef cattle but often lack essential minerals like selenium and zinc. Ranchers typically provide these nutrients through mineral supplements—a possible vehicle for adding red seaweed or its active ingredient bromoform to cattle diets.
In previous studies at Sierra Foothill REC, both seaweed intake and bromoform consumption varied widely among animals. The measurement equipment also posed challenges; laser methane detectors required confining each animal individually for several minutes, limiting sample sizes. Additionally, researchers could not track individual supplement intake—data were averaged across groups rather than attributed to specific animals.
“We didn’t have any way to measure individual intake or control individual intake,” Barry said.
To overcome these issues, the current study uses two technologies: a “Smart Feeder” system that dispenses mineral supplements only when it detects an animal’s RFID ear tag—measuring exactly how much each cow consumes—and a “Green Feeder” device that attracts cows with alfalfa pellets while sensors continuously monitor their breath for methane emissions.
“The Smart Feeder records exactly how much mineral each individual animal is consuming, which will also allow us to calculate how much red seaweed they are ingesting,” Warner explained.
The Green Feeder acts as a vending machine for cows: it dispenses treats when animals place their heads inside so sensors can record gas concentrations over several minutes.
“The Green Feeders measure methane but, in order to do that, the animals have to use these feeders for about three to five minutes,” Barry said.
Researchers encountered several obstacles using these systems in remote terrain—such as unreliable solar power during rainy weather—which required backup generators and installation of solar-powered satellite internet connections. Delays pushed some activities into calving season when many cows had newborn calves present.
“Using this technology on rangeland is proving to be very challenging, so we have had to go through a lot of troubleshooting,” Warner said.
Team members credited colleagues at Sierra Foothill REC—including Jordan Munson who manages the cow herd—for supporting day-to-day operations despite technical difficulties related to equipment maintenance and weather conditions. Chloe LeMaire handled mixing supplements while maintenance staff adapted facilities for solar panels and weatherproofing.
“We have the machinery, we have the brain power, we have the passion, and we have the employees with the stick-to-it-iveness – so we’re able to have a full-service research center here in Browns Valley,” said Nikolai Schweitzer, Sierra Foothill REC agricultural operations manager.
Barry emphasized that having access to livestock herds and dedicated staff at Sierra Foothill REC was essential: “The fact that we have livestock there – and people who can manage the livestock – that’s just instrumental… You couldn’t do this elsewhere; we wouldn’t have been successful in getting funding to do a project like this without the research center.”
The study will continue through 2027 under Barry’s leadership with collaborators including Warner; Josh Davy (UCCE advisor for Tehama, Glenn and Colusa counties); and Gaby Maier (UCCE specialist at UC Davis School of Veterinary Medicine).
UC Agriculture and Natural Resources shares science-based practices statewide through research centers like Sierra Foothill REC as part of its mission to enhance lives across California. It operates nine Research and Extension Centers serving as living laboratories across diverse ecosystems and maintains offices throughout all 58 counties. As part of the University of California, UC ANR applies university expertise via outreach initiatives to benefit communities statewide.
