Cows produce less methane when they eat easily digested grains

WINNIPEG, Manitoba -- Cows would belch a lot less greenhouse gas if producers simply would change their feed to grain from grass, researchers say.

Ermias Kebreab recently analyzed cow burps at the National Centre for Livestock and the Environment near Winnipeg, Manitoba, to measure the amount of methane dairy cows produce.

The University of Manitoba scientist says his research shows that changing the feed reduced cow burps by 52 gallons of greenhouse gas per cow, per day.

"We focused on what's happening within the cow," Kebreab says.

Global warming report

About 98 percent of the methane from a cow comes out of its mouth, the rest from the other end of the animal.

Conventional wisdom holds that grass is less of a contributor to global warming than more energy-intensive crops like grain. Kebreab's report, published in the Journal of Animal Science, shows that may not be the case.

His research found grass-fed cows produced about 150 to 180 gallons of methane per day, compared with about 130 gallons per day per grain-fed cows.

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

It's estimated that 8.3 percent of Canada's emissions are caused by farming, and 32 percent of that is from cows.

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

Using the findings

For now, Kebreab's findings are being used in by the U.S. Environmental Protection Agency to assess its cattle-methane emissions. So far, Canada has not, says Kebreab, whose research is partly funded by the Dairy Farmers of Canada.

In Canada, national estimates of methane emissions rely on mathematical models such as the one recommended by the Intergovernmental Panel for Climate Change, Kebreab says.

"They don't take into account the kind of feed," he says. "Their predictions are not very accurate."

Kebreab says his study did not look at which resulted in more greenhouse gases overall -- cattle fed perennial grasses like hay or alfalfa, or animals who eat grain and all the energy consumed and pollution produced to harvest that grain.