The sabino coat coloration is a recessive trait. This means that a horse requires two copies of the gene in order to produce a sabino coat. If a horse has a sabino coat, it develops spotted white patterns. If a horse has only one copy of the sabino coat pattern (S/s), the horse usually has two or more white feet or legs. The white color will often extend up the legs to the belly in irregular or fragmented patches. These jagged white patches are commonly referred to as barrel spots or belly spots. The head of a sabino horse is moderately white and commonly has a blaze or white patch that expands the length of the face. The white areas of a sabino horse lack pigment, both in the hair and skin.
While other genes that cause white tend to have more defined and uniform patterns, sabino is a term often used for smaller, unpredictable areas of white on a horse. One common defining feature of sabino markings are the 'roaning' around the edges of the white markings. This is where the borders of the white markings intermix with the horse's base color, and where white hairs start to blend with the darker surrounding coat. The roaning gene has a similar effect and is often associated with sabino. However, the roaning gene is a separate gene from the sabino gene.
Similar to frame overo, sabino seems to work in a dosage effect. Horses that carry a single inherited copy of the gene will display the broken sabino markings and possibly only a small amount of white. A horse that carries two inherited copies of the sabino gene (homozygous, or s/s) will be almost pure white in appearance. Unlike frame overo, there is no life-threatening condition attached to the pattern.
The sabino-1 test is proven to determine a gene mutation linked to the sabino-1 coat pattern. The test determines whether a horse is negative, heterozygous, or homozygous, for the sabino-1 mutation.
|Homozygous: Horse has two copies of the Sabino 1 gene and may appear as a Maximum white sabino. Horse will pass a copy of the gene on to all offspring.
|Heterozygous: Horse has one copy of the Sabino1 gene. Horse will exhibit varying degrees of Sabino1.
|Negative: Horse is negative for the Sabino 1 gene.