Project at UC ANR center in Yuba County probes additive effectiveness on rangelands.

Previous studies have shown that adding red seaweed (Asparagopsis taxiformis) to beef cattle rations could reduce methane – a potent greenhouse gas – produced by the animals by up to 90%.

But those results were in controlled settings – not wide-open rangelands.

“The challenge now is finding a reliable method of delivering the seaweed product to cattle grazing on pasture,” said Andrea Warner, a University of California Cooperative Extension livestock and natural resources advisor for Sutter, Yuba, Placer and Nevada counties. 

“Cattle in feedlots or dairies are being fed a total mixed ration every day and they’re in a more controlled environment,” Warner explained, “whereas out here [on rangelands] we could have cattle grazing on several hundred acres of pasture.”

Scientists added red seaweed to a salt-based mineral supplement mix, which they put in “free choice” feeders – covered metal troughs – in the pasture. When they tried to measure results, they discovered two things. One, actual consumption of the supplement was inconsistent, with seemingly less efficacy in decreasing methane output. And two, their conclusions were limited by significant shortcomings in their data.

“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 is the first author of a study published last year, funded by the Russell L. Rustici Rangeland and Cattle Research Endowment, UC Davis. The authors concluded that additional research – with improved equipment and methods – was needed to better understand how seaweed additives could realistically be incorporated into grazing systems.

That’s why Barry, Warner and their collaborators are back with a new project at UC ANR’s Sierra Foothill Research and Extension Center in Browns Valley, Yuba County. This study is funded by the California Department of Food and Agriculture’s Livestock Enteric Methane Emission Reduction Research Program. 

The first phase of the project is running “palatability trials,” to gauge whether the addition of seaweed affects the cows’ consumption of the mineral. That will help the scientists determine optimal mineral mixtures. Subsequent phases will assess consistency of the cows’ consumption, verify any reductions in methane and measure impacts on livestock performance (i.e., weight change and body condition).

Research probes practicality of seaweed additives in grazing system

While methane produced by ruminants (cattle, sheep, goats, etc.) comprises only 6% of global human-related greenhouse gas emissions, curbing that methane is regarded as the “single most effective target for near-term climate change mitigation strategies.”

“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.

Livestock grazing, primarily by beef cattle, occurs across 34 million acres in California – about 33% of the state’s total land area. But those rangelands, which provide 70% to 80% of forage for the state’s grazing beef cattle, lack essential nutrients such as selenium, copper and zinc.

Thus, those minerals – usually in the form of a salty, sand-like product – are regularly provided to grazing cattle by ranchers. And that mineral supplement is a promising way to incorporate red seaweed (as well as bromoform, the active ingredient that reduces methane production) into the cattle diet.

But the first study of this approach conducted at Sierra Foothill REC ran into several problems. The amount of seaweed and bromoform consumed by the animals appeared to be highly variable.

Furthermore, the “laser methane detector” – a device that emits a laser beam and measures how much light is absorbed by methane – had its drawbacks. It required each animal to be confined to a chute for at least four minutes so their breath and burps could be measured, and this limited the number of cattle that actually produced usable readings.

Importantly, the study also didn’t track or account for individual consumption patterns – instead producing only averages. The “supplement consumed by each animal” was calculated by dividing the total amount of supplement consumed by the number of days in the feeding period and the number of heads in the test group.

“We didn’t have any way to measure individual intake or control individual intake,” Barry said.

The solution? Give the cattle electronic IDs.