22 Tex. Admin. Code § 573.32
A veterinarian holding a current certificate of special competence in a particular field of veterinary medicine issued by the respective specialty boards in veterinary medicine, recognized by the American Veterinary Medical Association, may state in reputable veterinary directories, advertising or notices mailed to veterinarians, clients, former clients, personal friends, and relatives; the yellow pages of telephone directories distributed in the geographical area or areas in which the veterinarian resides or maintains offices or had his/her primary practice; and on professional cards or letterhead that he/she is certified in a particular field in the following words: "Board Certified (e.g., Veterinary Radiology)." A veterinarian must indicate his or her specialty whenever the veterinarian indicates that he or she is a specialist.
22 Tex. Admin. Code § 573.32