So, just what is a Spotted Draft horse? The simplest way of producing a Spotted Draft horse is to cross a full draft horse breed (Belgian, Percheron, Clydesdale, Shire, Suffolk Punch or American Cr�me) with a Paint horse. The resultant foal is now a 1/2 draft and hopefully exhibits the tobiano or overo color pattern with a somewhat drafty build. Note that the possibility of creating a breeding stock (solid) colt exists. From here, the newly formed Spotted 1/2 Drafts are bred back to full drafts producing a 3/4 draft. Breeding a 3/4 draft to a full draft produces a 7/8 percent draft; now considered full draft.
Color genetics plays a key role in producing Spotted Draft horses. The goal is to produce well marked, drafty, colored foals. The most recognized pinto is the tobiano. A major feature of the tobiano is that white will appear to start somewhere along the spine and descend vertically. Characteristics include four white legs with irregular edges, ink spots or paw prints with dark hooves and patches of color around the chestnuts. Face markings are the same as on normal horses. Horses that possess different alleles in any gene pair are referred to as heterozygous and those which have the same alleles are called homozygous. Breeders try to select individuals that are known tobiano producers (through a high percentage of tobiano offspring even though the horse is hetrozygous for tobiano) or those that are homozygous. Because the homozygous horse has two copies of the tobiano gene it will produce 100%
tobiano progeny to a mate of any color. This is due to simple genetic rules; it only takes one copy of the tobiano gene to exhibit characteristics of the tobiano pattern.
Since mating results in each parent contributing one half of the genetic make up of the resulting foal, a homozygous individual will always pass one copy of the tobiano gene to that foal. The modifying genes, which control the extent of the white markings in the tobiano, are probably present in all horses, but rely on the presence of the tobiano gene to express themselves.
No color pattern has been the subject of as much confusion over its identification and inheritance as the overo. In many respects the overo is the opposite (or negative) of the tobiano. Overo displays as a dominant pattern of white patches that appears to spread horizontally along the ribs, neck and body, leaving the topline and legs still colored. Usually the face has large, asymmetric white often referred to as a "bald face". Often times an overo individual will have 'blue' or 'wall' eyes. An overo must have one overo parent, even if that individual is not completely marked. A homozygous overo foal is born white and soon dies after birth from lethal defects, most commonly defective bowel formation. This is known as "lethal white or white foal syndrome". By never breeding an overo to an overo but always to solid colored stock, a good percentage of overos do occur, but without the possibility of producing a lethal white individual.