Although a deadline is looming for significant changes in how livestock antibiotics are administered, farmers, veterinarians and feed mill owners still have plenty of questions.

That was the message last week during a session in Ames on the new Veterinary Feed Directive (VFD) rule issued by the Food and Drug Administration (FDA).

The VFD rule, which is a part of a plan to combat antimicrobial re­­sistance, requires a written statement issued by a veterinarian for the use of certain medicines in or on an animal feed.

Under the rule, which is effective at the beginning of October, avitamycin, florfenicol and tilmicosin will require a VFD for use in animal feed on the farm.

However, by Jan. 1, 2017, all medically-important antimicrobials for use in or on feed will require a VFD. That means drugs like neomycin, sulfamethoxine, chlortetracycline and others will be added to the list for ...