Contrary to urban legend, only 3 percent of a cow's methane come from its tail-end. The other 97 percent rises as a belch. Either way, livestock play a little-known role in global warming. Andre-Denis Wright, the new chair of Animal Science, has a bovine emissions plan. (Photo: Sally McCay)

Cows belch. This might not seem like a big deal unless you're writing Emily Post Visits the Farm. But within those belches lurks methane, a potent greenhouse gas.

An average U.S. beef cow burps up more than a hundred pounds of methane each year, thanks to bacteria in its gut. Multiply this by 99 million cows — and about 2 percent of the U.S.'s contribution to global warming comes out of the mouths of livestock.

"In America, agriculture alone produces more greenhouse gases than all the industries, transportation and animals in Australia — combined," says Andre-Denis Wright, who arrived from Australia's national science laboratory at the beginning of September to take a new post as the chair of UVM's department of Animal Science.

Wright aims to improve these statistics — and help farmers at the same time.

A tough emission

At UVM, he will continue his decade-long quest to develop a vaccine that targets the methane-producing bacteria in the front stomach, or rumen, of livestock. "The big goal is to increase their efficiency of digestion and reduce their environmental footprint at the same time," he says, pointing to a photo of a protozoan taken through an electron microscope. "This free-living guy is about 20 microns." It looks like a gigantic gray sack with a tail.

"Now, look at these little guys here," he says pointing to what look like rice grains stuck to the outside of the sack. "These are the bugs that produce methane."

A large population of these bugs, or methanogens, is not only a problem for global warming, it also signals that an unnecessarily large portion of the cow's food isn't feeding the cow.

Some methane production is inevitable if cows are going to discharge the hydrogen that would otherwise build up in their anaerobic guts. But Wright believes it's possible to develop a vaccine that both cuts emissions and also increases milk and meat production. "If you can reduce methane production, you're returning some of that energy back to the animal," he says. "That 2 percent to 15 percent of the gross energy intake (used by the bacteria) is lost energy for the animal and lost profit for the farmer."

Wright projects that a successful vaccine in dairy cows could increase milk production by 5 percent or more.

Ruminants, including cows, need bacteria in their gut to survive — they break down plants, making protein and nutrients available. But some bacteria are better than others.

"You have good bacteria breaking down the cellulose and the lignen," in grass and other plants, says Wright, which, combined with cud-chewing, makes the plant digestible. "And you've got the bad ones that are producing the methane. We want to develop something that will target the bad guys and leave the good ones there."

In a previous experiment, highlighted in the journal Nature, Wright and his former colleagues in Australia were able to do that: in 30 sheep, they demonstrated that a vaccine could reduce methane output by almost 8 percent.

"But in subsequent experiments, we got different results," Wright says, "the vaccine was too specific. For various regions and diets it wasn't as effective," because a different assortment of bacteria are present in different places and seasons.

The vaccine takes an organism already in the animal's gut — either a methanogen itself or a related protozoan — and presents them to the animal's immune system so that the animal generates antibodies against it, Wright says. Then, the antibodies go into the saliva and the saliva inoculates the animal's rumen.

"The trick is getting something that covers all the methanogens from A to Z," he says. "If we're going to design strategies and protocols for reducing methane-producing bugs we need to know about the bugs were trying to get rid of," he says. And that opens a big can of bacteria.

Life's distribution

"I'm interested in the origin and distribution of all eukaryotic life," Wright says. Born and raised in Nova Scotia, he received a doctorate at the University at Guelph in evolutionary biology. "My key question now," he says, "what's the diversity and distribution of these methane-causing bugs?"

To answer that, Wright has traveled the world, collecting gut bacteria from South American birds, Norwegian reindeer, dromedary camels and Australian wallabies. He's also exploring the new science of metagenomics that uses computers to help sort the DNA from the great swamp of microorganisms living in an animal's gut — only 15 percent of which can be cultured and grown in a lab.

"Kangaroos produce undetectable amounts of methane, a thousand times less than cattle," Wright says. Since they evolved in Australian isolation, their gut bacteria are very different than what lives in a ruminant.

"I wonder," he says, "could you put those into cows?"