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 [email protected]).Learn more about sponsor message choices: podcastchoices.com/adchoices)NPR Privacy Policy)
