The launch of the Food and Drug Administration’s pilot testing program for tetracycline of one of every 15 milk tankers July 1 means dairy farmers and their hoof trimmers will need to religiously follow treatment protocols established by the farm’s veterinarian.

A further wrinkle is that hoof trimmers no longer are be able to supply tetracycline. The practice of using tetracycline to treat digital dermatitis, or hairy heel warts, falls under the new Veterinary Feed Directive. That means the dairy farmer must have a valid veterinary-client-patient relationship with a licensed veterinarian that is familiar with the farm and its practices. The veterinarian must first establish a protocol for the treatment of digital dermatitis. Then the farmer is empowered to buy the antibiotic prescribed by that protocol, and can give the antibiotic to the farm’s hoof trimmer for use.

Gerard Cramer, a veterinarian and hoof care specialist with the University of Minnesota, says that applying 2 grams or less of tetracycline per lesion for a maximum of two lesions per cow will not cause a violative residue in individual cows. But two grams is a very limited amount, and hoof trimmers who are used to shaking on  unmeasured doses of antibiotic need to be aware of dosage size.

And there’s a complicating factor. The tolerance level for tetracycline is 300 parts per billion, and some of the tests being used can detect tetracycline at lower levels. “I’m a bit concerned that some samples from smaller herds will turn up positive but not be violative,” says Cramer. “Farmers should talk to their veterinarian and their veterinarians should consult with FARAD (Food Animal Drug Residue Avoidance & Databank) and other sources” for milk withholding concerns.

“In some cases, your veterinarian might be uncomfortable with the risk of potentially contaminating the milk supply and include a milk withdrawal period,” says Cramer.

Another problem is that are no proven treatment alternatives. “But we do know a lot on the prevention of digital dermatitis and prevention should be the focus,” says Cramer. “When we make prevention the focus, what we use for treatment becomes less important as clinical disease can become sporadic.”