Bay, a classic and enduring equine coat color, has captivated horse enthusiasts for centuries. From the fiery chestnut points that contrast sharply against the diverse shades of the body coat, bay horses exhibit a stunning range of variations.
This guide delves into the fascinating world of bay color genetics, exploring the intricate interplay of genes that produces this iconic coat. We’ll journey through the rich history of bay horses, highlighting famous individuals that have left their mark on the world of equestrian sport and culture.
Finally, we’ll examine the various horse breeds that proudly display the bay coat, showcasing the diversity and versatility of this timeless color.
Color Features of Bay
- Base Color: Bay (A_ / E_)
- Genetics: Created by at least ONE copy of DOMINANT Extension (E) and at least ONE copy of DOMINANT Agouti (A)
- Ideal Coat Color: There is no ‘ideal’ bay coat color per se but we all have our favorite shade of bay!
- Coat Shade Range: Light reddish brown to very dark brown/black
- Mane and Tail Color: Black
- Points (Legs, Ears): Black unless there are white markings present
- Eyes: Normally hazel, dark brown, or black unless there is a coat pattern gene present, in which case they may be multi-colored, or blue (wall eyes).
- Skin Pigmentation: Normally dark with pink skin under white markings
- Markings: Usually standard – may have white on the legs and face. However, bays with coat pattern genes i.e. frame overo, tobiano, Lp, etc. Often display white markings consistent with that gene.
- Common Coat Variations: Low point (previously called wild type bay): has minimal black on the legs, often restricted to the fetlocks and below
- Standard: can range from orange red to blood red Dark: the darkest shades of bay and can appear almost black.
- Common Breeds: As the ancestral color of domestic horses, bay occurs in almost all breeds. The Cleveland Bay is exclusively bay and a few other breeds have a very high predominance of bays – Clydesdales, Standardbreds, and several of the Warmblood breeds.
Genetics of the Bay Horse Color
Fun but important facts about bay horse color genetics:
- Horses, and mammals in general, can produce only 2 pigments – black and red.
- Horse melanocytes produce red pigment by default but more on that a bit later.
- Horses also have just 3 base colors – bay, black, and red (chestnut).
- Each of the 3 base colors is produced by a particular combination of alleles at 2 genes – the MC1R or Extension gene (E), and the ASIP or Agouti gene (A).
- These combinations act as switches to turn black pigment production on or off.
- When black pigment production is switched off, the equine melanocyte (pigment producing cell) produces red pigment.
- Bay predates black and as mentioned previously, is the ancestral color of all modern domestic horses.
- Bay does NOT derive from black, and black does NOT derive from bay. Nor is bay ‘black-based’ (a common misconception). They are 2 different base colors.
Or to put it another way:
- A bay horse can produce BOTH black and red pigment.
- A black horse only can produce black pigment.
- A red or chestnut horse can only produce red pigment.
Bay Horse Color Genetics
All bay horses, regardless of shade, carry at least one copy of the dominant Extension allele (E) and one copy of the dominant Agouti allele (A).
Between them, these 2 alleles switch black pigment production on but at the same time restrict it to the points so melanocytes on the body produce red pigment instead. This produces the classic red body and black points of the bay horse.
Bay Horse Color Variants
It’s very easy to get carried away with bay horse color variants and try to name every single variation in shade. However, for the purposes of identification, most breed and performance registers prefer to simplify things, which is why you’ll find only a handful of universally recognized shades of bay.
It’s also important to note that things like nutrition and sun bleaching also modify coat shades independently of genetics. A ‘light’ bay for example could just be lacking essential minerals, like copper and zinc.
Copper is a core ingredient in the manufacture of red pigment. A dietary deficiency will divert whatever copper there is to life-sustaining organs – brain, lung, liver, kidneys etc – at the expense of red pigment production. Low levels of red pigment = light red, faded looking coat!
Here is an overview of bay horse color variants:
- Low Point Bay (ex Wild Type Bay): Coat color varies but is usually similar to standard bay. The defining feature is the restriction of black on the legs to the pastern or fetlock and below (hence the name ‘low point’).
- Light Bay: Light red coat – may be caused by a copper deficiency rather than genetics.
- Standard Bay: Clear medium red/brown coat with standard black points. Some bays in this shade range have a more golden hue to their coat and may be called ‘copper bays’.
- Blood Bay: Deep blood red coat, often with a purplish hue.
- Mahogany Bay: Dark red/brown coat with a lot of black hairs throughout.
- Dark Bay (ex Brown): Dark brown, near black coat and can be confused with black. Some very dark bays are only identified as bay via DNA testing.
- Seal Bay: Dark brown, near black coat with reddish brown, tan, or mealy coloring on the muzzle, around the eyes, and through the stifle and girth areas.
Common Bay Horse Breeds
There is only one exclusively bay horse breed – the Cleveland Bay.
As the ancestral color of the domestic horse, bay is reasonably common in almost every breed bar a small handful in which it has been purposely bred out. There are several breeds in which it is also quite uncommon and some in which it is by far the most common coat color. This latter group includes breeds like the:
- Clydesdale
- Standardbred
- Hanoverian (dark bay and seal bay are common)
- Holsteiner
- Oldenburg
- Australian Stock Horse
- Thoroughbred
8 Famous Bay Horses
There are many famous bay horses around the world, past and present, but here are a few of our favorites:
Figure (Justin Morgan’s Horse)
Known as the founding sire of the Morgan horse breed, Figure was a small yet immensely strong bay stallion. His compact build, versatility, and exceptional stamina made him legendary in 18th-century America.
Figure was celebrated for his ability to outpull larger draft horses, outpace Thoroughbreds, and excel in various equestrian tasks. His legacy lives on in the Morgan breed, renowned for its elegance and adaptability.
Copenhagen
Included in our list fo the most famous horses in history, Copenhagen was a distinguished bay Anglo-Arabian stallion that served as the Duke of Wellington’s horse during the Napoleonic Wars. Known for his bravery and stamina, he became a symbol of loyalty and strength, earning a place in equestrian and military history.
The Byerley Turk
The Byerley Turk, captured during the Siege of Buda in 1686, became one of the three foundation sires of the Thoroughbred breed. This dark bay stallion, often mistaken for black, served as Captain Robert Byerley’s war horse before becoming a breeding legend. His bloodline contributed to the development of one of the most successful racing breeds in the world.
The Darley Arabian
An attractive oriental bay stallion and the second of the 3 Thoroughbred founding sires courtesy of his chestnut great great grandson, the mighty Eclipse. He was purchased specifically for breeding purposes and today some 95% of male Thoroughbreds trace back to him in direct sire line descent through Eclipse, making him the most successful and enduring of the ‘Famous 3’.
Godolphin Arabian
This dark bay stallion, the youngest of the Thoroughbred foundation sires, was originally a gift to King Louis XV of France before being brought to England.
Known for his companionship with a stable cat, the Godolphin Arabian’s legacy continues through his grandson, Matchem, a cornerstone of modern Thoroughbred bloodlines. His story is a mix of charm and historical importance.
War Admiral
Despite his small stature, War Admiral was a powerhouse on the racetrack. This dark bay Thoroughbred won the Triple Crown in 1937 and went on to become one of the most famous American racehorses.
As the son of Man o’ War, War Admiral carried on his sire’s legacy, earning fame and admiration for his speed and tenacity.
Cardigan Bay
The first Standardbred to win $1 million dollars in prize money, the plucky little bay gelding was born in New Zealand and raced in Australasia until he was 8 before heading to North America where he eventually made his million at the age of 12.
Nasrullah
Nasrullah, a dark bay Thoroughbred, is celebrated as one of the most influential sires in racing history. His descendants include legends like Bold Ruler and Secretariat. Known for his fiery temperament and exceptional speed, Nasrullah’s legacy dominates Thoroughbred bloodlines to this day.
