07/06/2009 05:12 am ET Updated May 25, 2011

Change In Diet Could Curb Cows' Carbon Emissions

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.