No person other than California-licensed veterinarians who have obtained a license from the Board shall administer to any horse within the inclosure any veterinary treatment or any medicine, medication, or other substance recognized as a medication, except for recognized feed supplements or oral tonics or substances approved by the official veterinarian, or except under the direction or prescription of a veterinarian licensed by the Board.
Cal. Code Regs. Tit. 4, § 1840