A veterinarian, when caring for and treating a patient, shall conform to those minimal standards of care and treatment which are customary among veterinarians in this State. If a veterinarian professes to the public or colleagues to be a specialist in a particular area of veterinary medicine, the veterinarian, when caring for and treating a patient, shall conform to the minimum standards of care and treatment which are customary among these specialists. A veterinarian may not provide professional services while: Using any narcotic or controlled dangerous substance, as defined in Criminal Law Article, Annotated Code of Maryland; or Under the influence of alcohol or any drug that impairs that veterinarian's judgment or motor skills.