You are right, they are born alive, but the digestive tract doesn't fully develop, so when they eat, they can't digest the food, and soon get colicky and die. It's best to put them down rather then let them suffer a painful death. Some people have tried to do surgery and connect the intestine through to the rectum, I'm not sure if it's ever been successful or not. They are born pure white and thus the name lethal white.
