What is a Homozygous Tobiano Paint Horse?

The Tobiano (pronounced: tow be yah' no). The Tobiano coat pattern is governed by a dominant gene, meaning that there only needs to be one copy of the gene for the tobiano coat pattern to be present. Homozygous refers to having identical alleles for a single trait. Homozygous: (Ho-mo-zi-gus) means two copies of the same gene. Horses that are homozygous for the tobiano gene will have two copies of the tobiano gene, one inherited from each parent. A horse must have two tobiano parents to have inherited two tobiano genes. If the foal gets a tobiano gene from each parent this means the foal will be homozygous for tobiano. Only genetic testing will tell you more conclusively that the horse is homozygous for the Tobiano gene. Most labs only require you to collect sample by pulling (do not cut off) 20-30 mane or tail hairs with roots attached. This test is necessary because a lot of the times the value of the horse will go up if he/she is tested to be homozygous for tobiano gene. Especailly if this is a breeding stallion this test is important because many people do not want the gamble of getting a solid colored foal if they can breed to a stallion that will be a guaranteed color producer. If the sire is tested homozgyous tobiano and the dam is also tested homozygous tobiano then normally a test is not needed if you can prove that both the sire and dam have been tested.

The white on the body will generally cross the topline of the horse. Tobiano Paint Horses have the most common spotting pattern, characterized by rounded markings with white legs and white across the back between the withers and the dock of the tail, usually arranged in a somewhat vertical pattern. The head usually dark and with markings like that of a normal horse. i.e. star, snip, strip, or blaze. The body can be many different color patterns but again normally will have white legs. If the Tobiano Horse is Homozygous Tobiano (will always produce a spotted foal) the pattern may have what we call "paw prints" or lots of small black spots within the white. See photos below of a weanling homozygous tobiano paint colt and a homozygous tobiano paint stallion.

The tobiano pattern in horses and ponies appears to be inherited as a simple dominant gene. A spotted foal can be produced by a tobiano x non-tobiano mating, but never from a non-tobiano x non-tobiano mating. Tobiano foals with only one spotted parent will not breed true for tobiano because they have received a "Not-tobiano" gene from their solid parent that they will pass on, at random, to half of their progeny. The mating between two tobianos can produce true breeding (homozygous) tobiano horses. Breeders that can recognize homozygous horses may use them to breed so that "every" foal has the tobiano pattern. The tobiano coat pattern gene in the Paint or Pinto horse is a dominant gene, whereas, the "overo" coat pattern has a recessive gene. The tobiano paint horses can consist of just about any color, size and shape. Any breed of horse can be homozygous tobiano as long as you have the tobiano gene from each parent. No more worries about getting that solid colored foal with breeding homozygous tobiano horses. We need to make sure we don't sacrafice the quality when wanting to breed homozygous tobiano horses and make sure that they have the quality needed along with the color guarantee. Breeding for quality should be your top priority and the color is always a bonus.