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Cow Stomachs

June 26, 2007

A listener asks: Why do cows have four stomachs?


Why four stomachs are better than one. I’m Bob Hirshon and this is Science Update.

Listener Andrew Rains of Old Town, Florida, emailed to ask why cows have four stomachs. We turned to physiologist Hannah Carey, president of the American Physiological Society. She says cows need all the help they can get to extract energy and nutrients from the low-quality food that they eat. So the first and second stomachs house loads of bacteria and other microbes that break down grass and hay into something the fourth stomach can digest.

HANNAH CAREY (American Physiological Association and
University of Wisconsin-Madison):
The fourth stomach is the one that’s most like yours and mine. It’s the true stomach and it does many of the things that our stomach does.

As for the third stomach, Carey says it mainly just connects the second to the fourth. And if you can stomach more science, call us with your question at 1-800-why-isit. You could win a Science Update mug. I’m Bob Hirshon, for AAAS, the science society.