Thoroughbred horses come in many colors, but the question of whether a Thoroughbred can be grey often comes up. Grey is an unusual color in Thoroughbreds, but it does naturally occur. In this article, we’ll take a deep dive into Thoroughbred coat colors, genetics, and look at some famous gray Thoroughbred racehorses.
What Makes a Horse a Thoroughbred?
Thoroughbreds are a specific breed of horse that originated in 17th and 18th century England for racing. They are known for their speed, agility, spirit, and athleticism. To be considered a Thoroughbred, a horse must be conceived by a registered Thoroughbred stallion and out of a registered Thoroughbred mare. Thoroughbreds must also be able to trace their lineage to one of three foundation stallions – the Byerley Turk, Darley Arabian, and Godolphin Arabian. These stallions were brought to England from the Middle East in the late 17th and early 18th centuries and bred to native English mares. Their offspring became the first Thoroughbreds.
Common Thoroughbred Coat Colors
Most Thoroughbreds are bay, dark bay, brown, or chestnut in color. Here are some of the most common coat colors seen in Thoroughbreds:
- Bay – Varying shades of reddish-brown body color with a black mane, tail, and lower legs. Bays can range from bright copper penny red to a deep mahogany color.
- Dark Bay – Very dark shades of reddish-brown approaching black as the body color. The mane, tail, and legs are solid black.
- Brown – Varying shades of brown body hair with black legs, mane, and tail. Brown is a very common Thoroughbred color.
- Chestnut – A reddish body coat ranging from light red to dark liver chestnut. The mane and tail are usually the same shade as the body coat but may be flaxen (lighter). Legs are usually unmarked.
These colors – bay, brown, dark bay, and chestnut – likely make up at least 90% of all Thoroughbred coat colors. However, Thoroughbreds can also come in other unusual and striking colors such as gray, roan, palomino, buckskin, cremello, and perlino on rare occasions.
The Gray Gene in Thoroughbreds
Gray is an extremely rare color for Thoroughbreds to have. So how does it happen? The answer lies in genetics.
For a horse to be gray, it must inherit one copy of the dominant Gray gene (G) from one of its parents. The Gray gene causes progressive depigmentation of the hair, turning a horse’s coat progressively whiter as they age. Horses that inherit the Gray gene are usually born bay, chestnut, or black and then their colored hairs are gradually replaced with white hairs over time. Eventually they become almost completely white.
Since the Gray gene is dominant, a horse only needs one copy to express graying. However, the gene is relatively rare in Thoroughbreds. Most gray Thoroughbreds trace back to a small handful of horses born in the late 18th and early 19th centuries that carried the gene. Breeders have selectively avoided producing gray Thoroughbreds for the most part, so there are very few Gray gene carriers in the general Thoroughbred population today.
Famous Gray Thoroughbred Horses
While rare, there have been some exceptional gray Thoroughbred racehorses throughout history. Here are a few of the most famous:
| Horse | Years Active | Notable Achievements |
|---|---|---|
| Native Dancer | 1952-1954 | – Won 21 of 22 career starts – Champion 2-year-old in 1952 – Champion 3-year-old in 1953 |
| Gun Runner | 2015-2018 | – 2017 Horse of the Year – Won $15.988 million in career earnings – Won Pegasus World Cup, Whitney Handicap, Woodward Stakes |
| Roar | 2013-2016 | – Won the Grade 1 Matriarch Stakes in 2013 – Earned over $1.7 million in career earnings |
Some other champion gray Thoroughbreds include Striking Bird, Roseben, How Now, Snow Knight, and Disco Lucky.
Famous Gray Thoroughbred Sires
In addition to outstanding racehorses, a few famous gray Thoroughbred stallions have stood at stud and passed on the Gray gene, allowing it to continue to crop up in the breed on occasion:
- Sir Ivor – Won Epsom Derby and 2,000 Guineas in 1968. As a stallion he sired 16-time Grade/Group 1 winner Solford.
- Clear Mandate – Champion sire in 1949, his gray offspring included Native Dancer.
- Dunmovin – Sired 2009 Kentucky Derby winner Mine That Bird.
- Ecton Park – Sired stakes winners Fastness and Smokey Glade.
Because these stallions could produce offspring carrying the Gray gene, it has not completely disappeared from the Thoroughbred breed.
Prevalence of Gray in Thoroughbreds
It’s estimated that less than 1% of all Thoroughbreds are gray. In the early 2000s, grays were thought to make up less than 0.5% of the global Thoroughbred population. While still extremely rare, gray may be becoming slightly more prevalent in the modern breed through selective breeding efforts to produce them.
In the 2018 Thoroughbred foal crop born in North America, 0.68% of all foals born were registered as gray. This equates to about 1 gray foal born for every 147 non-gray foals. To put how unusual gray Thoroughbreds are into perspective, other rare colors like palomino and buckskin occur about 10-20 times more frequently in the breed than grays.
Famous Recent Gray Thoroughbreds
While the numbers are small, exceptional modern gray Thoroughbreds are still being bred. Some recent famous grays include:
- Annihilator – Won Grade 1 Hollywood Derby in 2022.
- Big Bad Leroybrown – Won Grade 1 Frizette Stakes and earned over $1.5 million.
- Fight On Lucy – Won Grade 2 Santa Ynez Stakes in 2017.
- Greyvitos – Won Grade 3 Affirmed and Grade 2 Best Pal Stakes in 2016.
The success of these recent runners indicates there is certainly still room for grays to excel in Thoroughbred racing.
Breeding Gray Thoroughbreds
For a Thoroughbred to be born gray, it must inherit one copy of the Gray gene from one of its parents. This means:
- One parent must carry and pass on the Gray gene
- The Gray parent can be either the dam or sire – the gene can be passed down from either side
- The other non-gray parent does not carry the gene at all
Two gray parents will actually not produce a gray foal, because the foal inherits two copies of the gene and becomes non-gray (homozygous). The key is breeding one gray parent to a non-gray mate.
Here is an example breeding between a gray stallion and chestnut mare that could produce a gray foal:
| Parent | Coat Color | Gray Gene Copies |
|---|---|---|
| Stallion | Gray | 1 copy |
| Mare | Chestnut | 0 copies |
Breeding a gray carrier to a non-gray mate allows the Gray gene to be passed down and produce gray offspring about 50% of the time. Any foals that do not inherit the Gray gene will be whatever base color the non-gray parent is.
Registration Rules for Gray Thoroughbreds
Grays are indicated by the code “gr” on their registration papers. All Thoroughbreds in the United States and Canada are registered through The Jockey Club. The registry has special rules for registering gray foals:
- Grays are registered as “dark gray” at birth based on their likely original foal coat color
- The registry must be notified once a registered “dark gray” foal begins to show signs of graying
- The foal’s registration is then updated to note their current state of depigmentation
- Over time, the coat description evolves on paper from “dark gray” to “gray” to “white” as the graying process progresses
This allows The Jockey Club to accurately document the progression of gray coat changes that occur over time in registered Thoroughbreds.
Famous Gray Thoroughbred Lineages
While rare, gray can run strongly in certain Thoroughbred family lines. Some famous gray lineages include:
- Descendants of Ingleside – Traces to Disco Lucky, Annulment, How Now
- Descendants of Missy Baba – Traces to Native Dancer and Apache Maid
- Descendants of Aspidistra – Source of gray in Gun Runner’s pedigree
Through selective breeding over many generations, these family lines have continued to produce exceptional gray-colored Thoroughbreds.
Value of Gray Thoroughbreds
The rarity and striking appearance of gray Thoroughbreds often makes them draw greater interest as racing and breeding prospects. However, gray has no correlation to performance ability – gray coat color alone does not make a horse any faster or more talented.
In the sales ring, the novelty of their color may increase a gray’s perceived value and demand compared to similarly bred chestnut or bay horses. However, buyers need to be careful not to get caught up bidding based on color alone. The best gray Thoroughbreds combine exceptional talent with their unusual coat color.
Conclusion
While the vast majority of Thoroughbreds will never carry the Gray gene, on very rare occasions it does crop up. Some of the most legendary racehorses throughout history just happened to be grays, showing the spectacular talent the gene can produce when combined with quality bloodlines. Moving forward, it will be exciting to see these glamorous gray athletes continue to occasionally grace the track.
