Food and Drug Administration authorities are reexamining "zero-day" withdrawal and milk discard times for drugs used in food animals.
Agency officials are seeking comments that could indicate how much time elapses between treatments and when animals are milked or slaughtered. But they noted that they have no indication current drug uses are a food safety concern.
Comments are due Oct. 8. Details are available at regulations.gov under docket number FDA-2019-N-3019.
In the request, FDA officials are asking how long it takes to transport animals from farms or other production facilities to slaughter plants, how often dairy cows are milked, and how veterinarians and others involved in raising livestock interpret drug-label language such as "zero-day withdrawal period" or "zero-day milk discard time."
In the 1980s, agency officials established the concept of "practical zero" withdrawal or discard times for some drugs after considering how long it took to transport animals to slaughter plants or how often they were milked.
"The FDA recognizes that the animal agriculture industry has undergone significant changes since the 1980s when the current assumptions about transit time to slaughter and milking frequency were formulated," the announcement states.
To apply a "zero-day" label to a new drug, studies need to show any residues in meat or milk would have depleted to safe amounts at the "practical zero" withdrawal times or milk discard times.
"Accordingly, we currently assign a zero-day withdrawal period or zero-day milk discard time to new animal drugs if data from scientific studies or other available information confirm that residue concentrations in edible tissues or milk from treated animals are safe for human consumption after 6 hours withdrawn from drug for poultry or after 12 hours withdrawn from drug for cattle, pigs, sheep, goats, and lactating dairy animals (i.e., practical zero withdrawal and practical zero-milk discard time)," the announcement states.
The agency didn't apply the same concept to egg-laying hens, aquatic animals, or bees.
One comment submitted by a dairy farmer indicates most of his cows are milked three times daily, and the time between when a dairy cow is selected for culling and it arrives at a slaughter plant could be as little as 30 minutes. He also said the Federal Register notice introduced him to the idea of a "practical" withdrawal or milk discard time.