By Jayna Pellett
We are celebrating Splash of Color throughout the month of February on YourDressage! Whether your horse is a registered breed of color, sports a painted or spotted coat, or wears lots of chrome, this month is for you!
Did you know that dressage riders who choose a colorful horse as their dressage mount are eligible for special awards through the Adequan®/USDF All-Breeds Awards program, as the American Paint Horse Association (APHA), Barock Pinto Association USA, and many others are participating organizations?
Who Painted Those Ponies?
A pinto or paint describes a horse whose coat features large patches of white, displayed as a result of various unique genetic combinations. These larger, patch-type patterns appeared shortly after humans domesticated horses (4000-2000 BC), evidenced by the genetic analysis of two 5,000-year-old horses with tobiano and sabino genes and human depictions of them in artwork and pottery.
Though many different breeds can have patterned coats, some breeds are much more likely to carry pattern-producing genes due to consistent selective breeding over time. One of the most notoriously colorful breeds is the American Paint Horse, an extremely versatile and flashy breed with one of the most popular breed organizations in the United States, the American Paint Horse Association (APHA). Since APHA is also a registry based on lineage, solid-colored horses can be registered if both of their parents are also registered.
On the contrary, some organizations require visible patterns to be eligible for registration, even sometimes on a particular base color. One such breed is the Barock Pinto, developed from Friesians and pinto-colored warmbloods to restore the diversity of patterns that used to exist in historical Friesian populations. According to the Barock Pinto Horse Association USA breed standard, these horses must have at least two white spots on the body with a diameter of at least 10 centimeters or be a proven tobiano carrier through genetic testing.
So, what are “tobiano” and “sabino” anyway?
The Patterns
Each pinto horse has a unique coat, but these patterns are not exactly random. Specific genes passed down from the horse’s parents contribute to these markings and produce a pattern with the same general characteristics every time. Currently, equine scientists have identified four main pattern-producing genes: frame overo, tobiano, sabino, and splashed white.
1. Frame Overo
Frame overo is a pattern characterized by irregular white patches, usually in a horizontal orientation, “framed” by any base color. These markings are often jagged in shape rather than smooth and rarely cross the back. Additionally, horses with this pattern usually have bold white face markings.
Frame overo is considered somewhat controversial due to its direct link to lethal white syndrome (LWS). LWS is a fatal disease affecting foals that are homozygous for frame overo, meaning the foal received a copy of the gene from both of its parents. However, with modern genetic testing, breeders can avoid crossing horses who both carry the gene.
2. Tobiano
Tobiano horses exhibit large, rounded white splotches spread vertically across their bodies, over their backs, and past the hocks and knees. However, white markings are often absent down the neck and chest in the appearance of a shield. These horses also feature facial markings that are more similar to those of traditionally solid-colored horses (star, strip, snip, blaze).
Bolder facial markings usually suggest the presence of other pattern-producing genes in addition to the tobiano gene. For example, horses carrying both tobiano and frame overo genes will display a combination of the two patterns, often referred to as “tovero.”
3. Sabino
Sabino-patterned horses have white markings that extend in varying degrees from the face and legs, often but not exclusively with speckling and roaning. At a minimum, sabinos usually feature white faces and stockings extending past the knees. Two copies of the sabino gene can nearly cover these horses in white markings/roaning.
Before widespread genetic testing, patterns were assigned based on appearance rather than lineage. As a result, several other genes can reproduce the sabino pattern, and a horse may be referred to as sabino without actually carrying the sabino gene. According to University of Kentucky researchers (Samantha A. Brooks and Ernest Bailey) who discovered the gene in 2005, sabino is found in the American Paint Horse, American Quarter Horse, Azteca, Miniature Horse, Missouri Fox Trotter, Mustang, Shetland Pony, and Tennessee Walker, while notably absent from the Arabian, Clydesdale, Shire, Standardbred, and Thoroughbred.
4. Splashed White
Horses with the splashed white pattern look like they have been dipped or “splashed” with white paint, feet first. Like the sabino, the head and legs are white, but these markings finish with a well-defined, blocky edge and rarely meet the top line. Bald faces with blue eyes are frequent, though not universal.
Six identified genes in several different breeds can create the splashed white pattern, with the most prevalent being found in the American Paint Horse, American Quarter Horse, Finnhorse, Icelandic Horse, Miniature Horse, Morgan, Shetland Pony, and Trakehner.
Dominant White
In addition to the four main pattern-producing genes, horses can have patterned coats if they carry one of several dominant white genes. Although dominant white horses are usually near- or all-white, they generally have dark eyes, and some can display sabino-like patterning. Thoroughbreds are known to carry several different dominant white genes, and the unique color has even swayed some in their breeding efforts. Since 2005, Megson Farms in Lexington, Kentucky, has made it their specialty to breed white and other uniquely colored Thoroughbreds.
Geneticists have uncovered many pattern-producing genes, but some coat colors and breed-specific genes remain relatively unknown, and their identification is a work in progress. For example, rabicano (limited roaning in a specific pattern, also called “white ticking”) is popular among color breed fanatics. Still, the responsible gene is one of many that have not yet been identified or formally investigated. Equine color genetics remains a study open to many discoveries, and we look forward to reporting on them in the future!
Stay tuned for the next installment of The Color Corner, which will explore another facet of Splash of Color Month – the spotted and dotted breeds!
