Cutting cattle's methane emissions.

• Position: Atmosphere - Brief Article

A peacefully grazing herd of cattle doesn't tend to conjure up visions of global warming, but the environment, the producers' bottom line, and the animals all could benefit if cattle produced less methane, the second-most abundant greenhouse gas. The world's agricultural livestock account for about 17% of the methane in the atmosphere. Cattle and other ruminant animals produce methane, a by-product of digestion, when organisms in their stomachs called methanogens break down fiber in grasses and grains they eat.

It is a waste of feed and energy, says biochemist Steve Ragsdale, University of Nebraska Institute of Agriculture and Natural Resources, Lincoln. "From five to 15% of the digestible energy in feed is lost as methane gas. Animal scientists have thought for 50 years that, if we could reduce the amount of methane produced by cattle, we could significantly reduce the amount of feed they need."

Ragsdale, animal scientist Jess Miner, and chemist James Takacs think they have found a way to do just that--cut the amount of methane cattle produce during digestion while boosting the amount of acetate, a compound the animal uses for energy. The result would be less atmospheric methane, less feed required, and more dollars in producers' pockets.

The team has designed chemical compounds that inhibit a key enzyme in methane production. When the enzyme is stopped, so is methane production. Takacs' lab has synthesized about 100 compounds that are potential inhibitors. Ragsdale tests them in methanogen cultures in his lab to see whether they block methane production. They have found four classes of compounds that inhibit the enzyme, but will they work in a cow?

"It's one thing to block methane in a monoculture in the lab, but it's a difficult challenge to block methane in a complex ecosystem like the rumen," Miner points out. The rumen is the first...