WASHINGTON – On June 28, guidance was issued on the use of antibiotics in livestock and poultry production by the U.S. Food and Drug Administration. The National Pork Producers Council (N.P.P.C.) says the proposal could lead to the elimination or costly review of previously approved animal-health products. The organization said there appears to be no science on which F.D.A. based the guidance.

NPPC stated the F.D.A. guidance calls for antibiotics that are “medically important” to humans to be used in animals only when necessary to assure their health. It also says those antibiotics should be administered with veterinary oversight or “consultation.” F.D.A. said the guidance would be used to develop public policy on animal antibiotic use.

“This guidance could eliminate certain antibiotics that are extremely important to the health of animals,” said Sam Carney, N.P.P.C. president and a pork producer from Adair, Iowa. “F.D.A. didn’t present any science on which to base this, yet it could have a tremendous negative impact on animal health and, ultimately, the safety of food. As we know, healthy animals produce safe food, and we need every available tool to protect animal health.”

Antibiotics that currently are not labeled for preventing, treating or controlling diseases could continue to be used if after undergoing a second rigorous F.D.A. approval process one of those label claims is proved. The process typically takes seven to 10 years and can cost antibiotics manufacturers millions of dollars.

N.P.P.C., which supports veterinary supervision, said regarding F.D.A.’s call for animal antibiotics to be used under the “oversight” of, or in “consultation” with, a veterinarian, it is concerned with the possible direction of the guidance. The association pointed out a requirement that all antibiotics be accompanied by feed directives, for example, could be problematic given the country’s severe shortage of large-animal veterinarians.

“Producers work with their veterinarians to develop animal health plans that include the judicious use of antibiotics,” Mr. Carney said. “The industry also has programs, including the F.D.A.-reviewed Pork Quality Assurance Plus program, that educate producers about the responsible use of antibiotics.”

The guidance, which does not have the force of law but may be treated as such by F.D.A., is a move to address an increase in antibiotic-resistant illnesses in humans, which opponents of modern animal agriculture blame on the use of antibiotics in livestock and poultry production.

Top scientists with the Centers for Disease Control and Prevention and the National Institutes of Health, however, recently told a U.S. House committee that there is no scientific study linking antibiotic use in food-animal production with antibiotic resistance.