Antibiotics have various residence times with the human body. Some are designed be highly soluble and pass through quickly whilst others have a longer residence time. This is related to the chemical structure of the anti biotic. The risk of addition to of anti biotics to two fold. Firstly continual unnecessary addition of antibiotics only serves to increase the chance of mutation for anti biotic resistant bacteria which can only serve to increase chance of a strain which effects humans and is difficult to treat with current antibiotics. Secondly as shown The New England Journal of Medicine (10/18/01) residence of these chemicals within the meat (which is then consumed) and other chemicals with unknown synergistic effects. This may (unproven) have the potential to accumulate in human muscle with unknown effects.