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Splashed White Overo
(SW-1, SW-2, SW-3)


Many splashed white horses are characterized by a large blaze, extended white markings in legs, variable white spotting in belly, pink skin, and often blue eyes. In other cases the unpigmented areas are quite small and can not be distinguish from horses with other more subtle depigmentation phenotypes. Typically though most splashed white horses look as though they where dipped in white paint feet first. The head, legs and belly may be white, sometimes connected to a patch running up either side of the thorax. The margins of the white markings are crisp, and well-defined.

Occasional congenital deafness is associated with white or white patterned, blue-eyed animals, including dogs and cats. It is important to note that most splashed white horses are not deaf. Hearing loss is due to the death of the necessary hair cells, caused by the absence of melanocytes in the inner ear. Although the majority of splash horses have pigment around the outside of the ear, the pigment must occur in the inner ear to prevent hearing loss.

Why test for splashed white?

Research suggests that the SW-1 allele arose several hundred years ago before the foundation of the modern horse breeds. Breed distribution of SW-1 includes Quarter Horse, Paint, Trakehner, Miniature Horse, Shetland Pony and Icelandic Horse and may be present in other breeds as well. Horses homozygous for SW-1 (SW1/SW1) have been identified, which suggests that this mutation is not homozygous lethal. Research also suggests that SW-2 and the rare SW-3 may only occur in certain lines of Quarter Horses and Paints. It is also speculated that SW-2 and SW-3 may be homozygous (two copies of the mutation) lethal and result in non nonviable embryos. It is there for not advisable to breed two horses that carry SW-2 or SW-3 as the risk of a nonviable embryo could be 25% and should be avoided.

Splash White Testing

Animal Genetics offers DNA testing for three markers resposible for splashed white (SW-1, SW-2, SW-3).


$25.00 US per sample.

Sample Collection

Collect sample by pulling (not cutting) 20-30 mane or tail hairs with roots attached. It is important that you pull the hairs and confirm that the actual root of the hair is being collected. The root contains the genetic material of your horse that is needed for DNA testing. Therefore, cut hairs do not provide an adequate sample of your horse's DNA. Place the collected hairs of each horse in separate zip-lock bags labeling the bags accordingly with the horses name or identification number. Download and complete a submission form for each sample and send along with payment to Animal Genetics for testing.


Results are given using the following symbolic notation:

Horse has two copies of the SW-1 mutation
Horse has one copy of the SW-1 mutation
No copies of SW-1 mutation

Possible homozygous lethal
Horse has one copy of the SW-2 mutation
No copies of SW-2 mutation

Possible homozygous lethal
Horse has one copy of the SW-3 mutation
No copies of SW-3 mutation

Animal Genetics, Inc.
1336 Timberlane Rd - Tallahassee, FL 32312
Toll Free: 866-922-6436

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