We all read about the beneficial effects of omega-3 fatty acids, found most commonly in fish oils in our diets. They buffer against cancer, reduce the risk of cardiac disease and may also improve brain and immune function. But in a presentation at the meeting of the Society for General Microbiology in Harrogate, UK today, Lorraine Lillis of University College Dublin and colleagues report a potential side effect in cows: Feeding them fish oil seems to reduce the amount of methane in their burps and farts.
Most people snicker at the statistic, but it’s true. According to a 2007 EPA estimate, at least 24 percent of methane emissions in the U.S. come from livestock flatulence. Livestock such as cows, goats, sheep and other ruminants – animals that have several stomachs and regurgitate food to chew it as cud – digest food in part by fermentation, which produces the greenhouse gas methane.
Lillis found that a diet that included 2 percent fish oil reduced the number of methane-producing bacteria in the cows’ guts. This isn’t a direct measure of methane levels in the cows’ “emissions,” but fewer methanogens should produce less methane.
The caveat here is that the experiment was done in only three cows. So if you have an organic farm, don’t run out and buy a truckload of expensive fish oil to feed to your free-range goats. Still, the idea holds promise and should be the subject of more study.