I watched the movie "King Corn" which is about how in america everthing is either fed corn or made with corn. Anyway they interviewed a guy who ran a feed lot for the cattle... he said that 80% of the anti-biotics used in the united states are given to cattle. And that the reason they use the anti-biotics is because the cattle go into acidosis from eating all that corn, which brings out legions and sores. However the cattle have to be slaughtered before 6 months of being on corn, otherwise they have worse health complications.