Sample

• 30 to 40 - hair roots - envelope

• 5 mL - blood - K3 EDTA tube

Turnaround time

• 2 to 5  working days

Why test?

• This genetic test can confirm is the horse is heterozygous (To/N) or homozygous (To/) for the Tobiano gene. For breeding purposes, homozygous Tobiano horses are highly desirable as they are guaranteed to produce Tobiano foals regardless of their mate.
• Since Tobiano is only responsible for the white markings of a so called “colored” horse, the test does not determine the horse’s base-color. This is determined using the extension test. The two tests in conjunction not only verify the likelihood of Tobiano being passed to foals, but also the likelihood the foals will be piebald or skewbald.

Results description

The DNA test verifies the presence of the chromosomal inversion and presents results as one of the following:

• N/ – Non-tobiano horse.
• To/N – Positive for the dominant Tobiano gene mutation, carrier of a single inherited copy of Tobiano. Horse’s base color may be modified to varying degrees by the Tobiano markings.
• To/ – Positive for dominant Tobiano gene mutation, carrying two inherited copies of Tobiano. Will always pass Tobiano to foals. For breeding purposes, homozygous Tobiano horses are highly desirable as they are guaranteed to produce Tobiano foals regardless of their mate.

Additional information

The Tobiano coat pattern usually involves some white on all four legs and rounded white spots on the body with sharp, clean edges.

The head of the horse is usually colored and will not have white caused by the Tobiano gene. The white on the body will generally cross the top-line of the horse.

Although white often incorrectly referred to as adding color it is actually a deletion of color. Tobiano is the result of a chromosomal inversion, affecting regulatory regions of the KIT gene. The Tobiano coat pattern is governed by the dominant KIT gene.

Only one copy of Tobiano gene (To/N) is required to express Tobiano coat pattern.

Homozygosity of the Tobiano gene (To/) may show visual clues (“ink spots” or “paw prints”) but only genetic testing will tell you more conclusively that the horse is homozygous for the Tobiano gene.

When there is no presence of the Tobiano gene (N), the Tobiano coat pattern is not possible.