Some critics of modern agriculture made a big deal of a study conducted by Michigan State University and USDA's Agricultural Research Service that found antibiotics in pig feed increased the number of antibiotic-resistant genes in pigs.
Scientists have known for quite some time that use of antimicrobials will select for resistant bacteria. But peer-reviewed risk assessments have shown that the risk to public health from antibiotic use in agriculture is negligible.
The MSU-ARS researchers did not look at the effects of antibiotic use in animals on public health outcomes but on animal health and production. The most interesting findings of the study were some clues on how antibiotics may actually help improve growth. It also showed how complex the connection between antibiotic use and resistance is.
Of course, while they were spinning the MSU-ARS findings, the critics ignored a recent study conducted by Dr. Scott Hurd, an associate professor at Iowa State University's College of Veterinary Medicine and a former USDA deputy undersecretary for food safety, that found greater amounts of salmonella bacteria on the carcasses of pigs that were sick during their lifetimes -- meaning they weren't given antibiotics that could have prevented their illnesses. It also found there was more sickness and salmonella contamination among pigs that came from antibiotic-free hog operations.