Cows break wind a lot, and their flatulence fills the air with methane, a potent greenhouse gas.
In fact, the EPA estimates that roughly 28 percent of all methane emissions related to human activity come from methane-producing bacteria in the rumens of domestic cattle, sheep and goats and other livestock known as ruminants, which eat plants that are mostly indigestible by other creatures.
By volume, methane is more powerful than carbon dioxide at trapping solar energy and making the atmosphere behave like a greenhouse.
Fish oil could cut down on the boom-booms, a new study suggests.
Specifically, including 2 percent fish oil in the diet of cattle reduces flatulence, apparently due to the omega 3 fatty acids in the oil. The study was a small one, however.
The technique cut methane output of three cows by 21 percent, said Lorraine Lillis of the University College Dublin.
"The fish oil affects the methane-producing bacteria in the rumen part of the cow's gut, leading to reduced emissions," Lillis said. "Understanding which microbial species are particularly influenced by changes in diet and relating them to methane production could bring about a more targeted approach to reducing methane emissions in animals."
Asked about the overall potential benefits fish-oil, Lillis told LiveScience she didn't know yet what effect it might have on a larger group of cattle.
She also acknowledged a possible shortcoming of the scheme: "There may be some trade-off as fish oil is expensive and difficult to get," she said.
Also not considered yet, she said, is whether it would put undue pressure on fish populations.
The findings are being presented today at a UK meeting of the Society for General Microbiology.
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