"The American meat industry is addicted to antibiotics. This dates to the late 1940s, when farmers discovered that antibiotics could do more than just cure disease. Antibiotics regularly mixed into feed could help animals avoid common illnesses -- and thus grow faster as well as better withstand the crowded and sometimes unsanitary conditions on factory farms.
Surveys over the last decade by the U.S. Department of Agriculture show that antibiotic usage has become routine: 84 percent of swine farms, 83 percent of cattle feedlots and 84 percent of sheep farms report that they add antibiotics or similar drugs to feed or water to promote animal growth. Some 70 percent of all antibiotics consumed by humans and animals in the U.S. are used by farmers for purposes other than treating animal diseases.The U.S. leads the world in this aggressive use of antibiotics. Frank M. Aarestrup, director of the National Food Institute at the Technical University of Denmark, reported in 2007 that American farmers used 250 to 300 milligrams of antibiotics per kilogram of meat produced. That was tops among the 20 countries Aarestrup compared."