The tobiano coat pattern is a highly desirable trait seen across a variety of horse breeds and types. The dominant tobiano gene causes loss of pigment leading to large white markings in certain defined areas of the horse. Tobiano horses are often referred to as 'colored' and are bred for this disirable trait.
Tobiano has the same effect on any base color. The following terminology defines the various types of tobiano specimens:
Piebald: A black & white tobiano horse.
Skewbald: Any other base color modified by tobiano, such as chestnut tobiano.
Tri-colored: Bay-based tobiano horse, 'tri-colored' refers to the three obvious colors on the horses body -white (from the tobiano) brown (bay) and often black patches are present also.
Since tobiano is a dominant gene, only one inherited copy is required for a horse to display tobiano markings.
Animal Genetics offers DNA testing for the tobiano gene. The genetic test verifies the presence of the tobiano mutation and presents results as one of the following:
|T/T||Homozygous||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.|
|n/T||Heterozygous||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.|
Since tobiano is only responsible for the white markings of a 'colored' horse, the test does not determine the horse's base-color. This is determined using the red/black factor 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.