The FDA took a significant step yesterday toward restricting the routine feeding of subtherapeutic (medically unnecessary) doses of antibiotics to livestock. As Grist has detailed in previous coverage, this practice — which by some estimates consumes nearly 70% of all antibiotics administered in the U.S. —  has been linked to the rise of antibiotic resistance, both in common pathogens such as salmonella and in previously rare ones such as MRSA. (For more on MRSA listen to Grist’s Tom Philpott speak with Superbug author Marilyn McKenna.)

A recent report from the American Society of Microbiologists on the growing threat of antibiotic resistance urged an end to industrial agriculture’s indiscriminate and virtually unregulated use of antibiotics as “growth promotants” in order to maintain the drugs’ effectiveness for people. Animals in concentrated animal feeding operations, or CAFOs, are routinely given antibiotics to help them tolerate the stressful, crowded conditions they are raised in; for an unknown reason, the drugs generally help them grow bigger, faster. Industry stands by the practice and downplays any risks it may represent to public health.

With legislation to restrict the use of antibiotics in livestock bottled up in House and Senate committees, both sides have looked to the FDA to take the lead. FDA Administrator Dr. Margeret Hamburg, as well as her deputy Joshua Sharfstein, had indicated their intention to act on the issue.

And now they have, in the form of what’s called “draft guidance.” Neither a full regulatory rule nor a law, it’s meant to establish procedures the FDA would like an affected industry to follow — and is subject to an open comment period before it becomes official guidance.

In the case of administering antibiotics to farm animals, the most important statement in this new document is that the “FDA thinks that using medically important antimicrobial drugs to increase production in food-producing animals is not a judicious use.”

While this may sound like so much bureaucratese, it represents a strong statement by the FDA and suggests further action is forthcoming. In addition, the agency declared itself to be particularly concerned about antibiotics that:

• Were approved before 2003
• Are used in food-producing animals to increase production;
• Are available over-the-counter (OTC), and therefore, can be given without a veterinarian’s involvement; and
• Are given continuously through the feed or water to entire herds or flocks of animals.

This draft, though clearly preliminary and subject to industry feedback, also gives Congress a reason to move forward on legal restrictions knowing that a scientific consensus is forming — though in reality it’s unlikely a law could be passed much before November, if at all.