Cattle: Mother Nature’s worst nightmare, apparently. Studies show that through their burps, cows emit between 200 and 400 pounds of methane gases each year, one of the most dangerous heat-trapping emission with ties to global warming, second only to carbon dioxide. In an effort on behalf of the cows to go green, farmers in Vermont are altering cattle feed to reduce methane emissions as part of an experiment conducted by yogurt company Stonyfield Farms. In mid-May, when results were last recorded, one herd showed an 18-percent drop in methane output. Milk production has stayed the same, and the cows’ coats are reportedly shinier and their breaths sweeter to boot. But since cows in the United States produce more milk than ever and fewer cows are needed to fill those milk jug quotas, the country’s methane emissions compared with those of less industrialized countries are low to begin with.