Published October 30, 2008 10:06 AM

Less grass means less gas, cattle researcher says

WINNIPEG - A University of Manitoba scientist says he's figured out how to cut the amount of greenhouse gas belching from cows by as much as 200 litres a day - feed them grain instead of grass.

For the past four years, Prof. Ermias Kebreab has been analyzing cow burps at the National Centre for Livestock and the Environment south of Winnipeg to measure the amount of methane dairy cows produce when they are fed different types of food.

About 98 per cent of the methane from a cow is emitted through its mouth - "only two per cent comes out the other way," said Kebreab.


Traditional wisdom holds that grass is less of a contributor to global warming than more energy-intensive crops like grain.

However, Kebreab's report, published in the Journal of Animal Science, shows that may not be the case.

On Wednesday, in a dairy barn, Kebreab recruited a gentle old Jersey steer named George to demonstrated how the study worked.

The bovine guinea pig was guided into a Plexiglas feeding compartment with a hooded collar around his neck to trap the gases.

A hose sucked the stinking gas out of the feeding area and into a machine that measured the methane.

Holstein dairy cows were fed grasses alternating every other week with grains.

The amount of methane they produced was measured.

The grass-fed cows produced 600 to 700 litres of methane per day compared to about 500 litres per day per grain-fed cow, said Kebreab.

That information could help Canada reduce its greenhouse gas and more accurately predict its methane emissions from cattle.

It's estimated that 8.3 per cent of Canada's emissions are caused by farming, and 32 per cent of that total comes from methane-producing cows.

Kebreab says the grasses cows eat are harder to digest than grains, so they produce more gas. Grain-fed cattle, meanwhile, produce more milk.

For now, Kebreab's findings are being used in the United States, not Canada, he said.

"We've developed the model here and the Americans use it," said Kebreab.

The U.S. Environmental Protection Agency has adopted the research to assess its cattle-methane emissions. So far, Canada has not, said Kebreab, whose research is partly funded by the Dairy Farmers of Canada.

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