It is allowed. I would consider that preventing disease in a particular herd for which it's known there's a disease pattern, as well as treating a disease, is important. Preventing disease, and the snowball effect of many more animals becoming much more sick, and having to use more antimicrobials, and maybe second line and third line treatments, is a reasonable practice. Yes, prophylactic drugs are approved for use in food animals in both prevention and treatment. They are permitted and considered reasonable.
