Flatulent cows are not a laughing matter. (Pause.) OK, they are a laughing matter. And flatulent sheep and goats are almost as funny — though not to the chickens and pigs in the pen next door. But pull-my-hoof livestock are a problem too.

The emissions produced by nature’s woodwind section contain a nasty mix of many gasses, among them methane. Though carbon dioxide is the first gas that comes to mind when we think of greenhouse emissions, pound for pound, methane is more than 20 times more powerful in terms of its global warming potential. Methane doesn’t linger in the atmosphere quite as long as CO2, and it’s not produced industrially in anywhere near the same quantity, but it does its damage all the same — and livestock toots out a surprisingly large share of it.

According to one Danish study, the average cow produces enough methane per year to do the same greenhouse damage as four tons of CO2. The average car, by contrast, produces just 2.7 tons. Multiply that by the planet’s 1.5 billion cattle and buffalo and 1.8 billion smaller ruminants and you have the methane equivalent of two billion tons of CO2 per year. According to the U.K. Department for Environment, Food and Rural Affairs (DEFRA), livestock account for about 4.5% of all of the country’s annual greenhouse gas emissions. Globally the figure is thought to be higher — about six percent.

Since nobody is going to re-engineer the ruminant digestive tract anytime soon, the solutions are limited: stop eating meat or at least eat other kinds. (A 2010 study from the Science and Environment section of the Library of the U.K.’s House of Commons reported that a pair of Australian biologists have recommended eating marsupials instead of livestock, since kangaroos and their kin produce almost no methane when they digest.) But there’s one more answer too: reformulate the diet of the animals themselves. If you change what goes in, you should be able to change what comes out.

That’s the conclusion reached by a just-released DEFRA study, which not only argues that traditional animal feeds must be replaced, but suggests what the new mealtime fare should be. The big three additions to the livestock lunch-line, according to the DEFRA scientists, should be maize silage, naked oats and grasses higher in sugars.

Maize silage, which, as its name suggests, is produced by fermenting corn shuckings in a silo or in covered heaps, can reduce tailpipe emissions by as much as 6%. Higher-sugar grasses can mean a 20% reduction, and naked oats—or oats without husks—reduce methane by a whopping 33 percent.

Changing the diets of farm animals around the globe will not be easy. U.K. animals already do eat some of the low-gas fare, but it makes up only about 25% of their diet. This would have to be tripled to 75% to make the advertised difference in subsequent wind. That’s an increase that, in the U.K. at least, the government seems willing to push.

“We are committed to supporting the farming industry as it faces the challenge of reducing its greenhouse gas emissions,” said Minister of Agriculture Jim Paice. “It is very exciting that…simply by changing the way we feed farm animals we have the potential to make a big difference to the environment.”

Farmers who blanch at the expense and inconvenience of such barnyard menu reform might think differently when they consider the alternative — and that alternative is not just a steadily warming world. In 2010, the U.N. proposed a global levy on livestock’s methane emissions, a measure that was promptly — and unavoidably — dubbed a fart tax in the press. A similar surcharge was proposed in the U.K. three years earlier, and farmers howled — though it’s arguable that this is one case in which the tax collector would dread an audit even more than the taxpayer. Still, when the U.N. proposal was first announced, Jonathan Surlock of the U.K.’s National Farmer’s Union did send an open letter to the Financial Times conceding that changing the animals’ diet was definitely preferable to taxing the consequences of not changing it.

The farm animals, of course, are aware of none of this, though they may one day wonder — if wondering is something they do — why their favorite foods have been replaced with something else. A cooler — if slightly less comical world — will thank them for their sacrifice.