The amount of antibiotics fed to health livestock dwarfs the amount used to treat people. As shown in Figure 2, our estimates suggest that eight times more antibiotics are used for non-therapeutic purposes in the three major livestock sectors than in human medicine. "Our estimates of 24.6 million pounds in animal agriculture and 3 million pounds in human medicine suggests that 8 times more antimicrobials are used for nontherapeutic purposes in the three major livestock sectors than in human medicine. By contrast, industry's estimates suggest that two pounds of antimicrobials are used in treating human disease for every pound used in livestock."
Source: Mellon, Margaret, Charles Benbrook and Karen Lutz Benbrook. "Hogging It!: Estimates of Antimicrobial Abuse in Livestock." Union of Concerned Scientists, 2001. http://www.ucsusa.org/food_and_agriculture/our-failing-food-system/indus... (Verified 04/18/14).