In the mid 1990s We have the history of 160 deaths in Europe from mad cow disease being transmitted to humans. Have we learned anything? Feeding animals back to animals communicated this disease. Today 1/3 to Â½ of dairy cattle suffer from mastitis. Others suffer from leukemia and lymphoma. High protein diets containing meat scraps, antibiotics, chicken manure, along with hormone injections into milk-producing cattle cause this unfortunate condition. Is our milk safe today?