Gray or Nay?

June 22, 2022

By Judy Stouffer, MSc
Introduction by Maribeth Kalinich

There are two questions many racing fans, both casual and avid, ask on a regular basis: 1) Why are gray horses so popular? And 2) What makes them gray? 

The latter question will be answered by Judy Stouffer in the proceeding essay. But first, let’s take a look at how the grey Thoroughbred has fared through its history.

The great horse breeder Federico Tesio studied color genetics and traced them back to the Alcock’s Arabian and the Brownlow Turk. Not a fan of grays, Tesio described a gray coat as “not itself a coat, but a pathological discoloration of the only two basic coats which are the bay and chestnut. It is a strange disease of the pigmentation.”

The color was all but bred out of the Thoroughbred in the 19th century due to superstitions that the gray horse was unlucky. This is thought to have originated from the color’s propensity to skin issues from lack of pigment and exposure to the sun. 

The color was rejuvenated through the sire line of Le Sancy (1884), a French stallion said to be the link to all modern Thoroughbreds.

For an image of Le Sancy click here.

Le Sancy‘s influence on the gray color cannot be understated. A multiple stakes winner and leading broodmare sire, Le Sancy sired Le Samaritan (1895) who in turn sired Roi Herode (1904). One of Roi Herode’s sons would end up being the biggest influence on modern gray racehorses.

That son’s name was The Tetrarch (1911). A gangly gray, he got his distinctive white body spots from maternal great-grandsire, Bend Or (a chestnut blotched with black and white spots). Years and years later, we can still see these spots on some of his descendants. 

The Tetrarch & jockey Steve Donoghue 1913 (Wikipedia Commons)

The Tetrarch was a champion racehorse and retired after injuries with a record of seven wins in seven starts. His most important contributions to the breed rest with his champion daughter, Mumtaz Mahal (1921), often referred to as “The Flying Filly.” Two of her daughters gave birth to colts that later became great sires – Mah Mahal (1928) was the dam of Mahmoud (1933) and Mumtaz Begum (1932) was the dam of Nasrullah (1940), a bay stallion and one of the founders of of the greatest sireline today.1

Modern superstitions consider the gray good luck especially a single gray running in a race. Bet the gray they say! 

In the mid-20th Century, the gray horse was the most popular horse in America. And the most popular athlete was named Native Dancer, the Grey Ghost. 

Native Dancer got his gray coat through his dam, Geisha’s line originating from Roi Herode (FR) in his fifth generation and passed down through all mares. 

Native Dancer romps in Withers Stakes at Belmont Park May 16, 1953. (The Morgan Collection – Keeneland Library A83403)

Writer John Eisenberg explains in his beautifully written book “Native Dancer: The Grey Ghose, Hero of a Golden Age.” The “Golden Age” it was the time after WWII when America was blooming with innovation and technology. And more and more families owned a television set. Albeit black and white.

Horse racing was the most popular sport in the country in the 1950s, just behind baseball. And it was televised. While most horses were bay, chestnut, brown or black and all looked dark and indistinguishable on a black and white TV a grey horse jumped out of the pack and off the screen. Viewers were riveted. Along came a horse everyone could cheer for. 

From the Introduction to “Native Dancer: The Grey Ghose, Hero of a Golden Age.” The “Golden Age””

[The 1950s] was the last decade without cynicism, the lives slower, choices fewer, and joys less complicated than what lay ahead. Racing was the playground of the thrill seekers. The sport was in a gritty golden age, perched atop the nation’s sports scene.

Native Dancer was the perfect horse for the moment. Before the din and anarch of the sixties, symbols of power were still beloved and embraced; institutions were to be admired, not challenged. The sports world was brimming with them. … Calumet Farm, racing’s dominant stable, had won the Kentucky Derby five times since. 1941. It was an age of winners, and America itself was the b

He was racing’s original pop star, the equine Elvis Presley, an iconic marker of an easier but unsettled time and place. When America was at its best in the early 1950s, its best was an indelibly charismatic horse knows as the Grey Ghost. “When Native Dancer came along, he was more than just a horse. He was a happening,” said Joe Hirsch, the longtime Daily Racing Form columnist. 

If not for a horse ironically named Dark Star and several alleged bumps during the race Native Dancer would have won the Kentucky Derby, the Triple Crown and ended his career with a perfect record of 22 starts, 22 wins. Alas, eclipsed by fate this was not to be. 

But this one disappointment did not deter fans from rooting for their rock star. And America’s love with the gray Thoroughbred racehorse was born. 

Now for a trip through the science of the gray Thoroughbred.

Naive Dancer became almost white in his older days as a stallion at Sagamore Farm. The Grey Ghost also became a sire of great sires and dams. This was taken outside of the stallion barn, date and photographer unknown. (Courtesy of Sagamore Farm.)

Gray or Nay?

The most common coat colors for Thoroughbreds are bay, brown and chestnut, followed by that pesky color, gray/roan. When is a gray Thoroughbred a gray, and when is it a roan?

The Jockey Club rules distinguish grays from roans as follows.

Gray: The majority of the coat of the horse is a mixture of black and white hairs. The mane, tail and legs may be either black or gray, unless white markings are present.

Roan: The majority of the coat of the horse is a mixture of red and white hairs or brown and white hairs. The mane, tail and legs may be black, chestnut or roan, unless white markings are present.

The tell-tale “eye-goggles” of a future gray, Electric Lettuce. (photo courtesy of Jaime Roth/LNJ Foxwoods)

This is a distinction based on how a horse’s coat color appears, its phenotype, and is the official definition of those colors as recognized by the Jockey Club. 

Under the hood, however, when DNA is examined, the genotype of all gray/roan Thoroughbreds (with one recent line that is a notable exception) comes from one or two inherited copies of a coat color gene geneticists identify as Gray, or G.

A Thoroughbred that is correctly registered under the Jockey Club rules as a roan reflects the phenotype of the horse: how it looks, with a mixture of red and white hairs in the majority of its coat. Its genotype, however, will be Gray.

Born a chestnut, Tapwater, is a 6-year-old filly by Tapit out of Fiji Moon by Indian Charlie. As you can see, the filly does not get her gray from her dam but from the very strong grey gene possessed by the formidable sire Tapit. (Foal photo courtesy of Jaime Roth/LNJ Foxwoods. Racing photo courtesy of Benoit Photo)

Researchers believe that a mutation occurred thousands of years ago in one horse ancestral to all modern breeds of horses that are gray. This mutation occurred when a segment of a gene in intron 6 of STX17, a gene which is found on the horse chromosome 25, was spontaneously triplicated when that horse was conceived.

All modern gray Thoroughbreds trace back to one gray stallion born in the 1700s, the Alcock Arabian. His line gradually disappeared, winnowing down to one gray broodmare born in 1787: Bab. Bab had ten gray foals, and through Bab and her offspring the gray color continued down through the centuries. All modern gray Thoroughbreds trace directly back to Bab and through her to the Alcock Arabian.

English Painting of early Thoroughbred sire the Alcock Arabian. c1720. Painter unknown.(Public Domain/Wikipedia Commons

The genotype for Roan, in contrast, is caused by a mutation in a completely different gene, called KIT, that is located on the horse chromosome 3. While Roan may have existed in early Thoroughbreds, it disappeared and was not found in any modern Thoroughbred until recently. 

Roan may have reappeared via a new spontaneous mutation (in the same place that it occurred originally in the KIT gene) in the New Zealand 1982 stallion Catch A Bird (Noble Bijou x Showy Countess). Catch A Bird sired four offspring that are phenotypically classic Roan: Odd Colours (1992 mare), Slip Catch (1993 mare), Goldhill Park (1994 horse), and Red Noble (1996 gelding). Slip Catch (Catch A Bird x Golden Belt (AUS)), the only one bred, produced two roans, Lavender Fields (2005 mare) and Lilac Hill (2000 mare). Lilac Hill produced a 2017 roan colt, Mathemagician (Holy Roman Emperor (IRE).

Another prime example is Dogtag. You can see her large white blaze still present through her transitional gray coat. A daughter of War Front out of the mare Diamond Necklace she gets her gray gene from her damsire Unbridled’s Song. (Foal photo courtesy of Jaime Roth/LNJ Foxwoods. Racing photo courtesy of Benoit Photo)

Gray is a “modifier” gene. It modifies the original pigment production that a horse has from the genes that determine its base color. All horses, no matter what coat color we see, are actually one of three basic colors: bay, chestnut or black. All other colors, like gray, come about through genes a horse inherits that modify the base color, dilute it or completely erase it so that no pigment is produced.

The Gray gene acts to gradually depigment a horse’s hair, until the coat color becomes all or mostly white. The Gray gene may also depigment the horse’s skin in a vitiligo-like pattern.

Gray can’t “hide” or seem to skip generations as Gray is a dominant gene that will always show in a horse’s phenotype.  Every foal that inherits Gray from either one or both of its parents will turn gray. While gray foals aren’t born gray, many but not all foals who inherit the Gray gene will have telltale gray hair “goggles” around their eyes, and gray eyelashes that are visible as soon as they have dried off after birth.

The tell-tale gray goggles are prominent on Electric Lettuce as a newborn foal. The daughter of Staight Fire born a bay, she gets her gray through her dam Propositioned from Tapit. (Foal photo courtesy of Jaime Roth/LNJ Foxwoods. Racing photo courtesy of Benoit Photo)

The Gray gene does not cause any known health problems in horses, with one important exception. A specific form of skin cancer is a very real concern for gray horses. Seventy to eighty percent of gray horses as they age will develop benign melanomas in the tail root, anal, perianal and genital regions, the perineum, the lips or eyelids. While they are not themselves dangerous, these melanomas can metastasize to internal organs, so watchful awareness for them and prompt treatment via removal is important for the health and longevity of a gray Thoroughbred.

The speed of graying, the amount of speckling, the incidence of melanomas and vitiligo-like depigmentation varies widely among gray Thoroughbreds. However, horses that inherit Gray from both their sire and dam in general turn gray more rapidly and are more evenly all white when they are elderly. There is some evidence that they also have a higher incidence of melanomas.

If owners are concerned that their gray Thoroughbred might have a copy of the Gray gene from both parents, equine genetic testing laboratories like the University of California-Davis Veterinary Genetics Laboratory can use a hair sample to cheaply test for the presence of one or two copies of the Gray gene (current price in 2022: $25).

Special thank you to Jaime Roth/LNJ Foxwoods, Kelly Coffman at Keeneland Library and Benoit Photo for assistance in obtaining photos.


A cis-acting regulatory mutation causes premature hair graying and susceptibility to Melanoma in the horse. Gerli Rosengren Pielberg, Anna Golovko, Elisabeth Sundstro, Ino Curik, Johan Lennartsson, Monika H Seltenhammer, Thomas Druml, Matthew Binns, Carolyn Fitzsimmons, Gabriella Lindgren, Kaj Sandberg, Roswitha Baumung, Monika Vetterlein, Sara Stromberg, Manfred Grabherr, Claire Wade, Kerstin Lindblad-Toh, Fredrik Ponte, Carl-Henrik Heldin, Johann Solkner & Leif Andersson. Nature Genetics July 20, 2008.

Pleiotropic effects of pigmentation genes in horses. R. R. Bellone. Animal Genetics 2010 #41 (Suppl. 2): 100-110.

Evaluating the potential roles of the Gray and Extension loci in the coat coloration of Thoroughbred racing horses. Takahiro Sakamoto, Jeffrey A. Fawcett and Hideki Innan. Journal of Equine Science Vol. 28 No. 2, 2017: 61-65

The equine graying with age mutation of the STX17 gene: A copy number study using droplet digital PCR reveals a new pattern. J. Nowacka-Woszuk, M. Mackowski, M. Stefaniuk-Szmukier, J. Cieslak. Animal Genetics 52 #2 April 2021: 223-227.

1: Horse Sense: 50 Shades of Grey (Thoroughbreds)

UPDATED 6/23/2022 3:20 AM

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