That's because sheep (and cattle) produce methane gas, the second-most important greenhouse gas after carbon dioxide.
The Kyoto Protocol -- the 1997 addition to the United Nations climate change treaty -- commits signatories, among them New Zealand and France, to limiting their greenhouse-gas emissions. So, in New Zealand and France, two groups of scientists have been finding out how to reduce the methane that sheep and cattle produce.
In New Zealand, an estimated 43 percent of New Zealand's greenhouse gases are methane and almost all of that comes from the country's 40 million sheep and 10 million cows. In France, 15 percent of that country's methane emissions come from the country's ruminant stock.
It isn't actually the sheep that produce the gas, but rather microbes in the animals' rumen, their first stomach. Those microbes make the gas after feeding off the hydrogen produced by other bugs.
http://www.wired.com/news/technology/0,1282,39654,00.html"
The Big Sheep Belch Squelch
In New Zealand, scientists have been measuring the levels of methane coming out of grazing sheep. They use halters around the mouth (the end most of the gas comes out of) to measure the amount of methane the animal is expelling. About 5 percent of grazing sheep produce up to 40 percent less methane than expected. "We don't know why that is," Joblin said.
By understanding the role of the microbes in both sheep reared indoors and outdoors, the scientists hope to find a solution to the methane problem. Whatever solution they arrive at, it's important that the right microbes -- the ones that digest the sheep's food -- are kept in place. "That understanding could lead to natural methods for controlling it," Joblin said.
http://www.scoop.co.nz/mason/stories/HL0102/S00127.htm"
Burping Cows Will Be A Political Issue!
The typical cow belches 280 litres of methane gas a day, which is 20 times more potent than carbon dioxide in greenhouse gas emissions, according to an Australian CSIRO study. A cow-burp tax might help solve the problem
