Radiation and radioactive materials aren’t just used for human medical purposes. Animals that are sick or hurt benefit as well, in methods similar to those used by medical doctors.
By far, the most common use of radiation in a veterinary practice is from x-ray machines. An x-ray machine uses electricity to produce low-energy radiation that passes through soft substances such as skin and muscle, but not through hard substances like bone or metal. So when a veterinarian suspects your dog has a broken leg, he uses an x-ray machine to obtain a picture, called a radiograph.
Radiographs can also spot objects that animals have swallowed by mistake, such as lead sinkers lost in a pond or stream by a fisherman.
While x-ray machines are regulated by state agencies, not the NRC, other activities performed by veterinarians do require an NRC license. One common radioactive material, technetium-99m or tech-99m as it’s often called, is used to diagnose bone damage too small to be seen by x-rays. This type of diagnosis, called a “bone scan,” is performed often in horses used for racing or jumping.
The horse is injected with a tech-99m-labelled compound that acts like calcium and concentrates in the bones. The compound emits low-energy gamma rays that can be detected by a “gamma camera.” Because most of the gamma radiation will come from the bony areas of the horse, a picture of the bone can be seen. Damaged areas will have high concentrations of the tech-99m, allowing the veterinarian to see what areas are causing pain. The radioactive material decays away in a few days. The horse can then go home and be treated for the problems identified in the bone scan.
Vets commonly use another isotope, iodine-131, to treat feline hyperthyroidism. This disease is caused by an overactive thyroid, 
and cats with this disease become very thin and sick. One possible treatment involves surgery to remove part of the thyroid, so that the cat’s thyroid activities are reduced to normal levels.
Or a veterinarian can use radioactive iodine-131, known as I-131, to reduce thyroid activity. In this type of treatment, a cat is injected with I-131, which will concentrate in the cat’s thyroid and emit gamma radiation that will damage some of the thyroid tissue and reduce thyroid activities to a more normal level. I-131 has an eight-day half-life, so cats treated with it must remain at the vet hospital for several days. Then owners must follow special handling precautions when they return home.
While technetium-99m and iodine-131 are the most commonly used radioisotopes for treating animals, some large veterinary hospitals may also use lasers, computed tomography scans, positron-emission tomography scans, and magnetic resonance imaging. And animals of all sizes, from hamsters to horses, from owls to elephants, may need x-rays – thus benefitting from the careful medical use of radiation.
U.S. NRC Blog 
The NRC and the EPA put out a document in 1980 titled, “Investigations of Reported Plant and Animal Health Effects in the Three Mile Island Area.” It is not available through the NRC’s web site (it exists only in the legacy library), but you can find it online here:
http://nepis.epa.gov/Exe/ZyNET.exe/91008J97.TXT?ZyActionD=ZyDocument&Client=EPA&Index=1976+Thru+1980&Docs=&Query=&Time=&EndTime=&SearchMethod=1&TocRestrict=n&Toc=&TocEntry=&QField=&QFieldYear=&QFieldMonth=&QFieldDay=&IntQFieldOp=0&ExtQFieldOp=0&XmlQuery=&File=D%3A%5Czyfiles%5CIndex%20Data%5C76thru80%5CTxt%5C00000011%5C91008J97.txt&User=ANONYMOUS&Password=anonymous&SortMethod=h%7C-&MaximumDocuments=1&FuzzyDegree=0&ImageQuality=r75g8/r75g8/x150y150g16/i425&Display=p%7Cf&DefSeekPage=x&SearchBack=ZyActionL&Back=ZyActionS&BackDesc=Results%20page&MaximumPages=1&ZyEntry=1&SeekPage=x&ZyPURL
The International Atomic Energy Agency’s Fukushima page has many links to various reports, some of which discuss impacts of the accident on animals and agriculture: http://www.iaea.org/newscenter/focus/fukushima/
Moderator
Speaking about Fido and Fluffy: How many pets and domestic livestock died or suffered cellular mutations as a result of Three Mile Island accident and the Fukushima-Daiichi accident?
It s wonderfull like I am a veterinarian:)
It’s certainly possible that small animals would be closer to any ground contamination and, therefore, would have different radiation exposure and contamination issues than people. Animals that groom themselves, like dogs and cats, would ingest some small amounts of radioactive materials. This may be different for larger animals. The Center for Disease Control provides some recommendations for your pets during a radiological emergency at http://www.bt.cdc.gov/radiation/selfdecon_pets.asp
Betsy Ullrich
Is it true that in the aftermath of nuclear power accidents, pets often suffer the first, as they are closer to the ground, their hair acts as an air filter picking up dust, and they lick themselves?