Tenn. Code Ann. § 67-6-350

Veterinarians shall be considered the users and consumers of all drugs purchased by them for use or resale in the practice of veterinary medicine. The drugs shall be subject to sales or use tax on the purchase price to the veterinarian; provided, however, that drugs used in the treatment of livestock and instruments used for the administration of drugs used in the treatment of livestock shall be exempt from tax. Veterinarians seeking to make exempt purchases of drugs, and instruments for the administration of the drugs, used in treatment of livestock or resold in the practice of veterinary medicine for treatment of livestock shall provide a fully completed Streamlined Sales Tax certificate of exemption to each dealer from which it intends to make the exempt purchases. Veterinarians shall be liable for tax on the drugs or instruments at the full rate provided by § 67-6-203 if the drugs or instruments purchased exempt were not used in the treatment of livestock or resold in the practice of veterinary medicine for treatment of livestock.