The issue of antibiotics in animal feed reared its head again Thursday as U.S. Sen. Elizabeth Warren (D-MA) questioned Food and Drug Administration Commissioner Margaret Hamburg about the effectiveness of Guidance 213 during a Senate Committee on Health, Education, Labor and Pensions (HELP) hearing. “Surely the removal of production uses from the market is a good first step, and I’m hopeful that this is going to lead to decreasing use of antibiotics, but the FDA’s guidance doesn’t guarantee the prudent use of antibiotics in the context of disease prevention,” Warren said. When FDA announced its final plan last December to phase out the use of antibiotics to promote growth in food animals, the agency gave industry 90 days to respond with their intentions to comply or not. That deadline passed this week, and members of the Animal Health Institute and the Generic Animal Drug Alliance have shared their written commitments to withdrawing approval relating to production uses and changing the marketing status of their products from over-the-counter to use by Veterinary Feed Directive (VFS) or prescription. “As of March 12, 2014, FDA has received responses from all of the sponsors affected by this guidance and is currently reviewing and analyzing those responses,” reads an agency statement. “We are encouraged by the positive response thus far.” But the responses haven’t put all minds at ease. “Even with every animal drug company agreeing to comply with the FDA’s most recent guidance, there could still be a lot of antibiotic use in animals that is ostensibly for disease prevention, but is still far more than necessary and will continue increasing resistance,” Warren stated during the hearing. It’s a concern echoed by many others, including Keeve Nachman, a scientist at the Johns Hopkins Center for a Livable Future. “While labels indicating use for ‘growth promotion’ will go away, there is concern that these drug products will be re-listed with new ‘disease prevention’ labels and still be used in the same way,” Nachman told Food Safety News. Such prophylactic uses involve low, subtherapeutic doses that can cover much of an animal’s lifespan, and public health advocates think it’s still a significant factor contributing to overuse and the rise of antibiotic-resistant bacteria. “We’ve heard from many of the manufacturers that they don’t expect complying with the guidance to affect their revenues, which suggests that these uses are going to continue under the name of prevention,” said Avinash Kar, an attorney for the Natural Resources Defense Council’s (NRDC) health program. “Do you really think the pharmaceutical industry is going to voluntarily walk away from such a huge chunk of their sales?” he added. “If it was actually stopping the problematic uses, I don’t think they’d be complying.” In response to Warren’s question about how the changes will ensure that the use of antibiotics in agriculture declines – and the risk of perpetuating resistance along with it – Hamburg said she believes they will make “a real and an enduring difference.” She also referenced the VFD, saying, “We’re also going to be moving the oversight of the use of these products to the supervision of a veterinarian, which isn’t the case now.” “But veterinarians are permitted to prescribe for anything that’s on-label use, so as long as they are permitted to use it effectively for preventive disease, that means that there’s the possibility of just continuing to keep these drugs out in circulation, keeping them out there all the time,” Warren countered. “We will be able to work in oversight of the prescribing practices of veterinarians,” Hamburg slipped in just as Warren’s time was cut off.