The belching inside Penn State University’s research dairy barn is constant.

“They burp gas all the time,” says animal science professor Alex Hristov, of his herd of 60 black and white Holstein cows.

For a place with so much burping, though, it’s eerily quiet, with just an occasional deep moo from a resident or two. The cows are happily corralled in two long rows of stalls, each animal with a yellow tag on her ear. More than a few are munching on feed.

“They milk about 100 pounds of milk a day,” says Hristov, proudly, with a Bulgarian accent. “They eat a lot, so they’re good cows.”

All that eating, of course, is responsible for the round-the-clock burping. And even though cow belches, or eructations, are silent, that doesn’t mean they go unnoticed here. Because the breaths contain methane, the scientists are keenly interested in finding a way to prevent them.

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