Ok, sorry for the confusion, we may be talking about two different things. Maybe you can post some articles supporting your theory of why low dosage antibiotics increase growth rates in farm animals. I'm only pointing out that there is research-a-plenty that supports what I'm talking about - those three (although I provided 6 links total) are there because I'm lazy and didn't want to spend more time gathering others. Like you pointed out, there is a very limited number of antibiotics that are given to animals (I don't know that it's only 3, but I may be getting confused with de-wormers), but in humans there are many types. From personal experience, they can affect your gut bacteria to the extend that all sorts of things can occur, things that are hard to trace back to the antibiotics.