“Pet shop” means any lot, building, structure, enclosure or premises whereon or wherein is carried on a business of buying and selling or bartering birds, animals or fowl; but this definition shall not be construed as applying to the buying or selling of livestock, nor to the business or activities of a duly licensed veterinary hospital, nor to the business or activities of the San Luis Obispo County Humane Society. (Prior code § 4003.2)