"Everybody knows that it is possible to have too much of a good thing -- and that is true also of antibiotic drugs, the great lifesavers of modern medicine. But the worst threat of their unrestrained use is not about doctors writing scrips for their human patients. It is about their regular use in treating farm animals who are not sick.
Farmers use drugs pre-emptively to keep livestock healthy, to promote growth and to compensate for the unsanitary conditions of industrial-style farms. It is estimated that 70 percent of the antibiotics used in the United States are fed to farm animals for nontherapeutic purposes.
One of the consequences of this profligate usage is the rise of 'superbugs' that have grown resistant to antibiotics and thus are less effective in treating humans. The most notorious example is MRSA, a type of staph infection, which kills about 18,000 American annually. Yet as some farmers have demonstrated both here and overseas, filling animals full of drugs is not necessary to make a living."