US Dairy Cows Are Very Genetically Similar. That's Not Good NPR science correspondent Dan Charles explains why most of the dairy cows in America are descended from just two bulls, creating a lack of genetic diversity that can lead to health problems. He also visits a lab at Penn State University where scientists are trying to change that. Follow reporter/host Emily Kwong on Twitter @emilykwong1234. Email the show at shortwave@npr.org.
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Most U.S. Dairy Cows Are Descended From Just 2 Bulls. That's Not Good.

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Most U.S. Dairy Cows Are Descended From Just 2 Bulls. That's Not Good.

Most U.S. Dairy Cows Are Descended From Just 2 Bulls. That's Not Good.

Most U.S. Dairy Cows Are Descended From Just 2 Bulls. That's Not Good.

  • Download
  • <iframe src="https://www.npr.org/player/embed/777498494/778305554" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

Unlike most dairy cows in America, which are descended from just two bulls, this cow at Pennsylvania State University has a different ancestor: She is the daughter of a bull that lived decades ago, called University of Minnesota Cuthbert. The bull's frozen semen was preserved by the U.S. Agriculture Department. Dan Charles/NPR hide caption

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Dan Charles/NPR

Unlike most dairy cows in America, which are descended from just two bulls, this cow at Pennsylvania State University has a different ancestor: She is the daughter of a bull that lived decades ago, called University of Minnesota Cuthbert. The bull's frozen semen was preserved by the U.S. Agriculture Department.

Dan Charles/NPR

NPR science correspondent Dan Charles explains why most of the dairy cows in America are descended from just two bulls, creating a lack of genetic diversity that can lead to health problems. He also visits a lab at Penn State University where scientists are trying to change that.

Dan's original reporting on the genetic lineage of US dairy cows is here.

This episode was produced by Brent Baughman and edited by Viet Le.