Tenn. Code Ann. § 63-12-142

Any licensed veterinarian or ancillary veterinary personnel employed by and working under the direct supervision of a licensed veterinarian who, in good faith, at such person's own initiative, renders emergency treatment to an ill or injured animal gratuitously and without making charge for such treatment is not liable to the owner of the animal for any civil damages arising from the treatment provided to the animal except in cases of gross negligence. If the licensed veterinarian or ancillary veterinary personnel acting under the direct supervision of a licensed veterinarian performs euthanasia on an animal, it is presumed that it was a humane act necessary to relieve pain and suffering.