Greening the Herds: A New Diet to Cap Gas

Chewing her cud on a recent sunny morning, Libby, a 1,400-pound Holstein, paused to do her part in the battle against global warming, emitting a fragrant burp. Libby, age 6, and the 74 other dairy cows on Guy Choiniere’s farm here are at the heart of an experiment to determine whether a change in diet will help them belch less methane, a potent heat-trapping gas that has been linked to climate change. Since January, cows at 15 farms across Vermont have had their grain feed adjusted to include more plants like alfalfa and flaxseed — substances that, unlike corn or soy, mimic the spring grasses that the animals evolved long ago to eat. As of the last reading in mid-May, the methane output of Mr. Choiniere’s herd had dropped 18 percent. Meanwhile, milk production has held its own. Sweetening cow breath is a matter of some urgency, climate scientists say. Cows have digestive bacteria in their stomachs that cause them to belch methane, the second-most-significant heat-trapping emission associated with global warming after carbon dioxide. Although it is far less common in the atmosphere than carbon dioxide, it has 20 times the heat-trapping ability. Frank Mitloehner, a University of California, Davis, professor who places cows in air-tight tent enclosures and measures what he calls their “eruptions,” says the average cow expels — through burps mostly, but some flatulence — 200 to 400 pounds of methane a year. More broadly, with worldwide production of milk and beef expected to double in the next 30 years, the United Nations has called livestock one of the most serious near-term threats to the global climate...NYTimes