Antimicrobials used to plump up production animals like pigs and cows while reducing overall food consumption are being phased out by a new FDA ruling released today, Reuters reported.

They aren't directly dangerous to animals or the food supply; rather, they are almost too safe. Antimicrobials are also used as medicine -- a sort of antibiotic -- to protect against infection in both animals and humans. As usage increases, the chances that bacteria will develop an immunity also increases, potentially rendering some medicines ineffective.

"Because antimicrobial drug use in both humans and animals can contribute to the development of antimicrobial resistance, it is important to use these drugs only when medically necessary," the FDA said in a release.

According to its plan, the FDA isn't banning production farms directly from using antimicrobial medication for their animals; rather, the government agency is asking pharmaceutical companies to voluntarily revise medication containing the microbe-fighting agent to current regulations. Once that process is complete -- it could take up to three years -- it would be illegal to use the drugs for production purposes. Farms wishing to use it as medication to treat sick animals could still do so, but would need veterinary oversight, according to the FDA.

"Implementing this strategy is an important step forward in addressing antimicrobial resistance. The FDA is leveraging the cooperation of the pharmaceutical industry to voluntarily make these changes because we believe this approach is the fastest way to achieve our goal," said FDA Deputy Commissioner for Foods and Veterinary Medicine Michael Taylor. "Based on our outreach, we have every reason to believe that animal pharmaceutical companies will support us in this effort."

Not everyone believes the FDA's open strategy is the "fastest way to achieve" its goal. Some critics wonder if companies will decide to ignore the plan as much as possible or use the drugs for the same overall purpose but write it off as disease prevention, Reuters reported.

"Our fear ... is that there will be no reduction in antibiotic use as companies will either ignore the plan altogether or simply switch from using antibiotics for routine growth promotion to using the same antibiotics for routine disease prevention," said Steven Roach, senior analyst with advocacy group Keep Antibiotics Working.

Still, several companies have already announced their intent to comply with FDA demands, according to Reuters. The FDA also has the right to take action against companies not following the rules.