As of this January (2017) any use of antibiotics in food or water WITHOUT a veterinarian is NOT allowed. This is called the veterinary feed directive. Now, yes this is associated with what we have heard for years, about feeding antibiotics to food animals for growth, increased body mass etc. However, this blankets ALL ANIMALS even BEES! Your pig, chicken, or pet rat is INCLUDED! So, anyone that self treats their pets, can be effected by this.
There are 2 parts to this. One is a list of drugs commonly placed in food. Regardless of commercial feed or not, you can't do it without a veterinarians ok.
This second list is for water. So any drugs bought OTC at a feed store that is on this list you can no longer add to water without a veterinarian.
Written by Dr. Kerri Cooper-Bailey, DVM