New Zealand seeks to curb livestock's gas emissions - Los Angeles Times

http://www.latimes.com/news/nationworld/world/la-fg-burp8-2008jun08,0,6244547.story --- Livestock produce an estimated 20% of the world's methane output, which also comes from landfill sites, coal mining, rice paddies and other sources. Methane and the even more potent nitrous oxide make up about half the greenhouse gases that New Zealand adds to Earth's air. Most of it rises from bucolic pastures where the country's iconic sheep and cattle graze, chewing, regurgitating and chewing again, and pumping out methane -- the bulk of it in their belches.

Would it be better to stop drinking milk ?

Cud-chewing farm animals produce a lot of methane because their food passes through a first stomach, called the rumen, where it ferments in a soup of saliva, bacteria and other microbes. Those bugs break down the food for digestion.New Zealand researchers are looking for ways to inhibit or eliminate a group of microbes called methanogens, which transform rumen gases into methane. They're also studying the animals' diet to see whether low-fiber, high-sugar substitutes will help the climate.