Mia's Painted Dream, owned by Janet & Cliff Tipton
Tobiano spotting is a pattern of white hair with underlying pink skin which can occur with any other coat color, and can occur in combination with other patterns. The pattern is present at birth and stable throughout life.
Tobiano is a coat pattern that is single gene dominant - in other words - a horse needs only to inherit a single Tobiano gene from one parent in order to show the pattern. If the horse carries the gene, it will show it.
Whether the horse carries one (heterozygous) or two (homozygous) Tobiano genes, the pattern will manifest itself.
Tobianos who carry two Tobiano genes (homozygous) may show visual clues, which include "cat track" spotting, "ink spots" etc., but if you want to know for sure, get the horse tested. Homozygous breeding stock is desirable to breeders, as their offspring will always be Tobiano.
The Tobiano gene is not related to Overo Lethal White, and will never produce a Lethal White. Qualification: The Tobiano Gene will not produce Lethal WHite. Tobiano Horses, if they also carry Frame (the gene that causes Lethal White when doubled up on) can and do. But it's the doublihg up on the FRAME gene that does the damage.
This is not to say that horses who show the Tobiano pattern are necessarily free of the OLWS gene, however. Tobiano and Frame Overo are separate genes, and it is both possible and not uncommon for a horse to carry both. The only safe route to avoiding the tragedy of Overo Lethal White syndrome is to have your breeding horses tested!
COLOR GENE TESTING
Both The University of California at Davis and Animal Genetics, Inc. of Florida can test for the presence of Tobiano, Red, Frame, Creme, Silver, Sabino1, and Agouti (Bay). The test for Tobiano can determine whether or not a horse is homozygous of heterozygous (good to know if you are trying to breed for Tobiano).
You can download forms for these tests from their website-- follow
OR, from the Animal Genetics website