Chad Dechow, a geneticist at Penn State University who studies dairy cows, is explaining how all of America's cows ended up so similar to each other. He brings up a website on his computer. "This is ...

There are more than 9 million dairy cows in the United States, and the vast majority of them are Holsteins, large bovines with distinctive black-and-white (sometimes red-and-white) markings. The ...

The drive to make more milk has had an unsavory side effect: Cows have become more genetically similar and less fertile. Scientists are trying to... Most U.S. Dairy Cows Are Descended From Just 2 ...