Last updated: October 9, 2026
Have you ever seen a horse with stripes running down its coat and wondered what you were looking at? Brindle horses have an unusual pattern that raises a natural question: how does a horse end up with stripes like that?
Here’s what brindle looks like, what actually causes it, which breeds have shown it, and whether you can breed for it.
Table of Contents
What Is a Brindle Horse?
A brindle horse has stripes running through its coat, a bit like a brindle dog, but usually less regular. Researchers describe the pattern as irregular vertical stripes in the hair coat texture along the neck, back, hindquarters, and upper legs. The stripes are often darker than the base coat, but on some horses they show up as lighter streaks or roan-looking bands instead.
Texture is part of it, too. In BR1 brindles, UC Davis notes that the hair in the stripes is less straight and unrulier than the rest of the coat, so the pattern can involve how the coat feels as well as how it looks. Because brindle sits on top of a base color, you’ll see bay brindles, chestnut brindles, dun brindles, and so on. It helps to know the common horse colors and patterns underneath it.
Don’t confuse brindle with the primitive markings on a dun. A dun can have a dorsal stripe down its back and zebra-like barring on its legs, but those markings follow a set pattern. Brindle stripes are irregular and can run across the whole body.
What Causes the Brindle Pattern in Horses?
Brindle isn’t caused by just one thing. Researchers have identified a specific gene variant in one line of horses, while other brindles turn out to be chimeras. Without testing, you can’t tell the cause from the stripes alone.
The inherited BR1 pattern
In 2016, researchers published a study in G3: Genes, Genomes, Genetics identifying a variant in the MBTPS2 gene in a family of Quarter Horses with brindle coats. The pattern was named brindle 1, or BR1. According to the UC Davis Veterinary Genetics Laboratory, BR1 is X-linked and semi-dominant. That means it’s carried on the X chromosome, and it doesn’t show up the same way in every horse that carries it:
| Result | Horse | What you’ll see |
|---|---|---|
| N/N | Female | No BR1 variant; doesn’t rule out brindling from another cause |
| N/BR1 | Female | BR1 coat-texture pattern expected; visible striping varies from horse to horse |
| BR1/BR1 | Female | Sparse mane and tail; no BR1 striped coat pattern |
| N | Male | No BR1 variant; doesn’t rule out brindling from another cause |
| BR1 | Male | May have a sparse mane and tail; no BR1 striped coat pattern |
That’s the surprising part: a stallion carrying BR1 doesn’t show the typical striped coat-texture pattern, but he can pass the variant to his daughters.
Chimerism
A chimera is a horse that carries two different sets of cells in its body. One way this can happen is when two nonidentical embryos fuse early in pregnancy, leaving the horse with cells from two separate genetic sources.
TheHorse.com described one well-known example, Dunbars Gold, a 1996 brindle Quarter Horse stallion that tested as a chimera with two DNA types. Chimerism happens by chance, so it isn’t inherited the way BR1 is, and it can show up in any breed.
Brindle Horse Breeds
There’s no such thing as a brindle breed. Brindle is a pattern that can show up in horses of different backgrounds, and the cause isn’t always known. Here’s what the available evidence tells us about the breeds and types of horses associated with it:
- Quarter Horses: The BR1 variant was identified in a Quarter Horse family, and the chimera Dunbars Gold was a registered Quarter Horse.
- Paint Horses: UC Davis lists Paints, along with Quarter Horses, as breeds the BR1 test is appropriate for. That doesn’t mean every Paint with a brindle-looking coat carries the variant.
- Warmbloods: The OMIA database lists the BR1 variant in warmbloods as well as Quarter Horses, though that shouldn’t be taken to mean the pattern is common in them.
- Thoroughbreds: Brindle Thoroughbreds have been reported, but the cause of an individual horse’s pattern may not have been confirmed (more on that below).
Since chimerism can happen to any horse, a brindle can turn up in just about any breed. For other unusual coats, see my guide to the rarest horse colors.
Are There Brindle Thoroughbreds?
Yes. One reported example is Catch A Bird, a Thoroughbred stallion in Australia that a brindle horse enthusiast site describes as having a brindle coat. The cited account doesn’t establish the genetic cause of his pattern, so it’s best to treat him as a reported example rather than proof of any particular genetic explanation. A striped appearance doesn’t tell you whether the cause is BR1, chimerism, or something else entirely.
Brindle isn’t a separate color category in The Jockey Club’s registration system. The American Stud Book rule book recognizes Thoroughbreds as bay, black, chestnut, dark bay/brown, gray/roan, palomino, or white, so a brindle Thoroughbred would still be registered under one of the official Thoroughbred colors.
How Rare Are Brindle Horses?
Brindle horses are exceptionally rare. Nobody keeps a reliable count across all breeds, but one historical figure gives you an idea of just how unusual the pattern is. TheHorse.com reported in 2010 that out of more than 4.7 million Quarter Horses registered with the AQHA, the registration department listed only 15 that had shown some form of brindle pattern. That number is old and it isn’t a current population estimate, but it shows how unusual the pattern was in the breed’s records at the time.
Can You Breed for a Brindle Horse?
Sometimes, if you know the cause. A brindle that’s a chimera won’t reliably pass the pattern on, because the stripes come from fused cell lines rather than an inherited gene. BR1 is different, since it follows predictable X-linked inheritance:
- A striped N/BR1 mare bred to a non-carrier stallion: Each foal has a 50% chance of inheriting BR1. Daughters that inherit it are expected to show the brindle coat-texture pattern, although the amount of visible striping varies. Sons that inherit it won’t show the typical BR1 stripes.
- A BR1 stallion bred to a non-carrier mare: All of his daughters inherit BR1 and are expected to show the coat-texture pattern. His sons don’t inherit BR1 from him because they receive their X chromosome from their dam.
If you have a brindle horse or breeding stock you’re curious about, UC Davis offers a brindle 1 test for Quarter Horses and Paints. A negative result doesn’t mean the horse isn’t brindle. It may just mean the pattern has a different cause, like chimerism, that the BR1 test doesn’t detect.
If you’re shopping for a brindle horse, be cautious about paying extra for a stallion advertised as a rare breeding prospect. Ask what evidence supports the claimed cause of his coat pattern. A BR1 test can identify that variant, but it won’t establish whether a horse with a different brindle-like pattern is a chimera. And even a BR1-carrying stallion won’t show the typical BR1 stripes himself.
A brindle is still worth a second look whenever you see one. Whether it’s a BR1 mare, a chimera, or something nobody’s tested yet, you may not run into another for a long time.
About Miles Henry
Racehorse Owner & Author | 30+ Years in Thoroughbred Racing
Miles Henry (legal name: William Bradley) is a professional horseman based in Folsom, Louisiana. He holds Louisiana Racing License #67012 and has spent over three decades managing Thoroughbreds at premier tracks including Fair Grounds, Delta Downs, and Evangeline Downs.
Expertise & Hands-On Experience: Beyond the track, Miles has decades of experience in specialized equine care, covering everything from hoof health and nutrition to training protocols for Quarter Horses, Friesians, and Paints. Every guide on Horse Racing Sense is rooted in this “boots-on-the-ground” perspective.
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