In December last year, the U.S. Food and Drug Administration introduced a set of voluntary guidelines touted as a "crack down" on non-medical use of antibiotics. The move was meant to address concerns about rising antibiotic resistance in bacteria that poses a health threat to people.

Legitimate Use

Livestock on conventional farms are often given low doses of antibiotics that, as a side effect, add extra pounds to animals before slaughter. The practice has been banned in the European Union.

The FDA's new rules, known as GFI #213, ask drug makers to advise against growth promotion on their label instructions, effectively barring the use of those antibiotics for fattening. The rules will be rolled out over the next three years, and drug companies have already expressed their willingness to comply.

To take something that's important for human medicine and use it just to make animals grow faster. That's a particularly bad use of antibiotics."

Critics say there's nothing to prevent farmers from using the same doses of antibiotics as a preventative "non-therapeutic" measure. Food and Water Watch took a close look at the labels for antibiotics used to promote growth, and found that 89 percent could still be given to healthy animals for other reasons.

According to Sarah Borron, a researcher with the group who led the project, only 23 out of 217 growth-promoting drugs have been completely removed for purposes other than treating sick animals.

"It's so egregious. I mean, to take something that's important for human medicine and use it just to make animals grow faster. That's a particularly bad use of antibiotics."

She said while farmers might argue for the legitimate use of drugs to head off disease, constant use of antibiotics isn't workable.

"If the system is essentially set up for the animals to get sick, and the only way to keep them from getting sick is to give them a low dose of antibiotics-always-that's a problem."

FDA Grilled

During a Senate hearing on Thursday, Massachusetts Senator Elizabeth Warren told FDA Commissioner Margaret Hamburg that the new guidelines were a good step, but failed to guarantee that farmers wouldn't keep using the drugs for the wrong reasons.

"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," she said.

In response, Hamburg said the addition of veterinary oversight under the new rules would help to curb misuse.

"There is a role for prevention," she said. "But we want to make sure that it's appropriate and adequately supervised, and especially when they are antibiotics of importance for human medical needs as well."

Warren said since veterinarians would be allowed to prescribe the same growth-promoting drugs for preventative use, the antibiotics could remain in circulation and continue to threaten human health.

"If we continue to use 30 million pounds of antibiotics in food animals every year, which is about four times as much as we use in people, we're likely to have a lot more resistant infections, and fewer antibiotics that work when we need them," she said.

Read More:

• FDA's Strategy on Antimicrobial Resistance (FDA)
• The Public Comment Period on an FDA Farm-Antibiotics Rule Closes Tonight (Wired)
• Warren Questions FDA Commissioner About Antibiotics Guidance (Food Safety News)
• Meat Industry Won't Fight Antibiotics Rule (Wall Street Journal)