An article was published on yahoo today, indicating that research has shown that the dairy industry's largest contribution to greenhouse gas emissions is produced by the cows themselves, but if they change the cow's feed to alfalfa, flaxseed and grass instead of corn and soy beans, the cows' enteric emissions can be reduced. Plus, they suffer from fewer stomach ailments. Here's a link to the article:
Feed a cow its natural diet instead of corn, and it is healthier for the cow and the planet. What a concept!