Tobiano
White patches that often cross the back
Tobiano produces white patches, often crossing the back. A horse can carry one or two copies of the associated DNA variant, and the amount of white does not reliably distinguish them.
Explanations and diagrams reviewed on 3 November 2026
Compare four ways color and white can be arranged
This example has large white patches crossing the back and extending toward the legs.
White patches appear on the sides, with colored areas framing them along the back.
The drawing shows colored spots on a mainly white coat. The leopard complex includes other appearances too.
White hairs mix with colored body hairs. Here, the head and lower legs retain more color.
What it looks like
Look for fairly rounded white patches, often crossing the back, together with white lower legs. The head usually keeps its base color apart from ordinary facial markings, and the skin beneath white areas is generally pink. Some horses show the pattern only subtly, with little more than white leg markings. These clues help you compare appearances, but a photograph cannot resolve every case.
Sources for this explanation [1]
What happens biologically
Tobiano is associated with an inversion on chromosome 3, one of the structures that package DNA in the cell. In an inversion, a stretch of DNA has been turned around. This rearrangement lies near KIT, a gene involved in the development of the cells that make pigment, and is thought to change how that gene is controlled. White patches reflect where pigmentation is absent; they are different from a dilution that lightens pigmented hairs.
Sources for this explanation [2]
Inheritance and DNA testing
The test uses TO for the tobiano-associated variant and N when that variant is not detected on a chromosome. The horse inherits one copy from each parent. N does not mean that the KIT gene is missing, and it says nothing about white variants tested separately. Tobiano is dominant: one TO copy is enough for the pattern to be expressed, although it may be subtle.
The three results read as follows: N/N means no TO copy; TO/N means one TO copy; TO/TO means two TO copies. A TO/N horse passes TO to about half its offspring, while a TO/TO horse passes it to all. For example, a DNA-confirmed TO/N × N/N mating has a 50% chance of a TO/N foal and a 50% chance of an N/N foal at each conception. Four foals are not guaranteed to include exactly two of each. The test establishes copy number; patch size does not.
Sources for this explanation [1]
Confusions, limits and health
Tobiano can occur with frame, splashed white or other white variants. The combined appearance is sometimes called tovero, but that name does not identify a single genotype. Tobiano does not tell you whether a horse also carries the EDNRB frame variant. Use the specific frame test when that risk matters for a mating. The outline of a parent’s patches does not predict the foal’s exact pattern.
An example: what could this foal inherit?
Region near the geneKIT
Both demonstration horses have the exact pair shown. These examples explain inheritance; they do not use the mare and stallion entered in the calculator.
MareN/TO
StallionN/TO
All possible pairs at each conception
- N/N25%
Two copies of N
- N/TO50%
One N and one TO
- TO/TO25%
Two copies of TO
Where the explanations come from
Laboratory resources explain which variants are tested and how to read their results. Research papers describe the evidence, discoveries and remaining uncertainties. Each article links its explanations to the relevant sources. Published titles stay in their original language so you can find the exact work.
1 · Laboratory explanation
UC Davis VGL — Tobiano2 · Research paper
Brooks et al. (2007) — A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses3 · Research paper
Santschi et al. (2001) — Incidence of the endothelin receptor B mutation that causes lethal white foal syndrome in white-patterned horses