Veterinarians diagnose and treat sick and injured animals, including pets, farm animals, native wildlife, sporting animals and more exotic animals, such as those kept in zoos or aquariums. They examine tissue, blood, urine and other samples to assist in diagnosing the cause of disease and decide on the appropriate treatment. Treatments may include prescribing drugs, surgical procedures and nursing care. In some cases they may also have to humanely kill an animal to end pain and suffering, or to prevent the spread of disease. Veterinarians also educate animal owners and breeders on techniques to maintain or improve an animal's health and/or welfare.