Breeding For High Milk Production Created Less-Fertile Cows
More Milk, Fewer Of These Guys Maryland Department of Agriculture After generations of careful breeding, dairy cows around the world produce more milk than ever. At the same time, they've actually become less fertile, a phenomenon farmers and researchers have worried about for years.* Now, a team of European biologists has uncovered one reason behind the decline, at least for several types of Danish cattle. The same genes that make cows produce more milk also kill off cow embryos, they found. The European researchers found that up to a third of Nordic Red Cattle are missing one copy of each of the same four genes. (Like humans, cows are supposed to have two copies of all of their genes, one from their moms, and one from their dads.) Having no copies of those four genes is deadly, but at the same...