FDA Plans Voluntary Campaign To Limit Animal Antibiotic Use

All Things Considered:

Today, the FDA unveiled a plan aimed at ending the use of antibiotics for growth promotion. It's the formal and more detailed version of draft guidelines issued in 2010, which lays out a roadmap for making it happen.
Rather than banning that use, the agency aims to collaborate with drug companies, veterinarians, and livestock producers.
  Update at 5:32 PM ET: That collaboration will be voluntary. Michael Taylor, the FDA's Deputy Commissioner for Food, says this will be a more effective approach, because any attempt to ban specific uses of more than a hundred separate drugs — and then defend each one in court — would be a hugely cumbersome undertaking: "Decades of effort, and millions and millions of dollars of resources."
Scott Hurd, a veterinary scientist at Iowa State University, says that the voluntary approach will have a real effect on farmers' practices. "Even though it's called guidance, people take it as the gospel and the law, so growth promotion usages will go away," he says.

I'll believe that when I see it.  I haven't run into too many farmers who took voluntary suggestions that go against labor-saving or bottom line enhancing practices.  Time will tell, but if the farmers don't, the voluntary will end up going away.