The birth of a white foal is a uncommon event. White horses make up less than 8% of the horse population and of those, most are actually grey. The grey horse is born a solid colour such as black, bay or brown with shadowy skin and some are born with rings around the eyes called “grey bulging eyes”. These bulging eyes disappear as the foal gets older and becomes increasingly white. This is caused by depigmentation due to the presence of the grey gene. Grey horses are often confused with white horses.
The white foal, on the other hand, is born with white fur, pink skin and brown or blue eyes and does not change color as it grows. In fact, the white appearance is caused by several overlapping white patterns that do not allow any of the base color of the coat to show through. A giant white patch, if you will!
Some argue that there are no true “white” horses because white is not a possible base coat color. To produce a “white” horse, a red, brown, or black base coat with additional genes for white spotting is required. Doubly diluted horses that carry two cream genes, such as cremellos, perlinos, and smokey creams, are often mistaken for white. One cream gene in a red or chestnut horse will result in a palomino, two of them will result in a cremello. A buckskin is a bay with one cream allele, while a perlino has a brown base coat with two cream alleles. A smokey black has a black base coat with one cream allele, while smokey cream has two. Cremellos, perlinos, and smokey creams are not classified as white, and may themselves have distinguishable white markings such as socks and blazes.
“Albino” is another term incorrectly applied to white horses with pink skin and blue eyes. Albinism is a condition in mammals characterized by a total lack of pigmentation, resulting in white fur, pink skin, and red-colored eyes. There is a uncommon breed called the American Albino, whose skin and coat lack pigmentation and have blue-colored eyes (never red eyes), which excludes them from being categorized as a true albino. Experts claim that there is currently no albinism in horses, as they have not found a horse that meets the criteria to be considered an albino.
Deadly white foal
One particular type of white horse strikes fear into everyone's heart: the dreaded Overo-Lethal-White Syndrome (OLWS) or Lethal White (LW), in which a completely white foal is either stillborn or dies shortly after birth because its intestines are not fully developed.
It is essential to note that not all white foals are fatally white. Fatally white foals result when each parent contributes a frame overo gene. Pigment is necessary for nerve function in the digestive system and the frame gene inhibits this. If only one frame gene is present (from one parent), there is no need to worry as the other non-frame gene is capable of maintaining normal digestive function on its own. On the other hand, if two frame alleles are present (homozygous, one from each parent), the digestive system is nonfunctional and death results.
Although a LW foal may be born alive and appear vigorous on the outside, it will inevitably die a painful death within a brief period of time or will need to be humanely euthanized to relieve its suffering. There is no medical cure for foals with this condition.
The frame coat pattern features white patches that do not extend beyond the back when viewed from the side, with the shadowy color “framing” the horse. Not all horses carrying the frame overo gene exhibit this coat pattern. Solid colored horses can also carry this allele, so it is essential to DNA color test mares and stallions from breeds that commonly carry this gene to prevent a fatal white foal. Quarter Horses, Paints, Appaloosas, Tennessee Walkers, American Saddlebreds, and Miniature Horses are some of the breeds known to carry the frame overo gene.
There is another white gene pattern that can lead to unwanted birth defects. The gene responsible for the “splash pattern” plays a role in the pigmentation and nerve function of the ears. The cochlea requires melanocytes (cells that produce pigment) to perceive sound. In splash mutations, these cells may be missing and the horse may therefore be deaf.
Puchilingui is one of the founding fathers of the Sabino thoroughbreds in North America.
Ancestral roots
My colored Thoroughbred mare American Iris recently gave birth to a white colt we named Jack Frost. She has a brown base coat with a dominant white spotting pattern due to the W5 KIT gene mutation. This instinctive white gene mutation began with the colored Thoroughbred sire Puchilingui and is only found in horses whose ancestors can be traced back to him. This pattern is also found in Anglo-Arabians or other crosses directly related to a Thoroughbred from this particular breeding line.
The foal's father is a warmblood. He is a solid bay with a blaze and socks. In order for him to produce a maximum white foal when mated to my mare, he must carry one of the white color markers, such as W20, which is common in warmbloods. A maximum white foal can result from any combination of white pattern genes that produce a pure white horse.
To avoid this mare having a maximum white foal, she would have to be mated with a “white killer” stallion that has had no white in itself or in its relatives for at least five generations. Her first foal was the result of mating with such a stallion. Pixie was born a palomino with a lot of white chrome.
One problem with white foals is that the skin around their eyes and nose is pink, making them vulnerable to sunburn. Solutions include applying zinc oxide to these areas or using a UV-resistant fly mask with a long nose. As a last resort, the eyelids can be tattooed. And finally, a white horse needs lots and lots of baths to keep him spotless and looking stunning!
