Fed Seaweed, Grazing Cattle Produce 40 Percent Less Methane

Grazing cattle fed a seaweed supplement produced close to 40 percent less methane than those fed grass alone, a new study found.

The microbes inside cows and sheep produce enormous volumes of methane, a potent heat-trapping gas released in burps and farts. By one estimate, livestock account for close to a third of our methane emissions. And grazing cattle produce more methane than either dairy cattle or feedlot cattle, owing to the fiber found in grass.

Scientists have previously shown that seaweed inhibits an enzyme that contributes to the production of methane, but the new study is the first to test the impact on grazing cattle.

For the research, researchers supplied seaweed pellets to a dozen beef steers on a ranch in Montana. Compared to cattle not given pellets, these steers produced 38 percent less methane, on average, with no impact on their size or health. The findings were published in the Proceedings of the National Academy of Sciences.

Research has found seaweed supplements cut emissions from dairy cattle by more than 50 percent and feedlot cattle by more than 80 percent, but those studies took place in controlled settings where cows were fed seaweed daily. In the new study, cattle ate seaweed voluntarily. Researchers say their method could be a model for ranchers.

“This method paves the way to make a seaweed supplement easily available to grazing animals,” said study coauthor Ermias Kebreab, of UC Davis. “Ranchers could even introduce the seaweed through a lick block for their cattle.”