>>FDA mandate wrt antibiotics for livestock and animal feed applies only to those used in human health
FDA has been under pressure for years by agricultural interests (and the GOP) to do nothing at all in this area. So I'm guessing they did what they could.
I know an expert (perhaps the expert on this issue) who tried to testify about this a few years back to a House Committee. It was a horror story - the GOP members basically wouldn't let him speak on the issue.