Mad Cow Disease

The reason why Mad Cow Disease started to spread and became a problem a few years ago was that the beef industry used to grind up some of the cattle parts that were not used for human consumption and put it back into the food supply of the living cattle, including brains and spinal cord. Since then they have determined that these parts, in particular, have more potential to be infectious and so they now only feed sheep to cows and vice versa.