Bay Horses: Coat Color Genetics

Bay is a common horse-coat colour, characterised by a reddish-brown or brown body with black points on the mane, tail, ears, and lower legs. This is caused by the interaction of two genes: the dominant Extension (E) gene, which allows for dark pigment in the coat, and the dominant Agouti (A) gene, which tells the dark black pigment where to go. Bay horses can range in colour from light copper red to mahogany bay, and dark bay.

Bay horses are reddish-brown with black points

Bay horses are characterised by their reddish-brown or brown body colour with black points on their mane, tail, ears, and lower legs. These black points are a key identifier of bay horses and without them, a horse cannot be considered a bay.

The reddish-brown body colour of bay horses can vary from a light copper red to a deep red blood bay, and even a very dark red or brown, which is sometimes called dark bay, mahogany bay, black-bay, or brown. The latter is so dark that it can appear almost black, with reddish-brown hairs visible only in certain areas of the body, such as under the eyes, around the muzzle, behind the elbow, and in front of the stifle.

The black points on a bay horse are caused by the interaction of two specific genes: the dominant (E) Extension Locus Gene, which allows for dark pigment to appear in the coat colour, and the dominant (A) Agouti Locus Gene, which tells the dark black pigment where to go.

The reddish-brown body colour of bay horses is caused by the pheomelanin pigment, while the black points are caused by the eumelanin pigment.

Bay is a dominant colour gene

The bay colour occurs when a horse carries at least one dominant Agouti gene (A) and at least one dominant Extension gene (E). The Extension gene is located on the MC1R locus and permits the expression of black pigment, while the Agouti gene is located on the ASIP locus and controls the distribution of black pigment to the points of the horse.

The bay colour is highly diverse, and there are several variations, including standard bay, dark bay or mahogany bay, blood bay, copper bay, light or golden bay, wild bay, and buckskin bay. These variations differ in the shades of reddish-brown or brown and the extent of black points.

Bay is one of the most common horse colours and is often regarded as the default horse colour. It is found in various horse breeds and is commonly seen in fields such as racing, performance, and other sports events.

Bay horses are born with lighter coats that darken with age

Bay horses are born with a more subtle shade of reddish-brown coat. As foals, they have black-tipped ears and dark manes and tails but a lighter colouring on their lower legs. They are also born with dark skin, making them look more like chestnut horses. Newborn bay horses also exhibit "foal fringes", which are light-coloured hairs outlining their tails. Once the baby sheds its foal coat, darker lower leg points become more pronounced while the fringes become more unnoticeable.

Bay horses are characterised by a reddish-brown or brown body colour with a black point coloration on the mane, tail, ear edges, and lower legs. These "black points" are their main identifiers. Without them, the horse can't be considered "bay". Bay horses have dark skin – except under white markings, where the skin is pink.

Bay horses are usually born with a lighter coat that darkens as they age. The sooty gene, which is not yet fully understood, appears to progressively darken some horses' coats as they get older.

Dark bay horses are often mistaken for seal brown horses

Bay is a common hair coat colour for horses, characterised by a reddish-brown or brown body colour with black points—black coloration on the mane, tail, ear edges, and lower legs. Dark bay horses have the darkest shade of bay colouring, with a deep brown, reddish body that can appear black or a very dark shade of brown.

Seal brown is a hair coat colour characterised by a near-black body colour with black points, but also reddish or tan areas around the eyes, muzzle, behind the elbow, and in front of the stifle. The genetics behind seal brown are not yet known, but it is believed to be caused by an allele of the agouti gene called At.

Another similar coat colour is liver chestnut, which has an all-over dark brown coat, including the mane and tail, but lacks the black points of bay horses and seal brown horses.

Bay horses are one of the most popular colours

The bay colour is caused by the interaction of two specific genes: the (E) Extension Locus Gene and the (A) Agouti Locus Gene. The (E) Extension Gene is dominant, allowing for dark pigment to appear in the coat colour. The (A) Agouti Gene tells the dark black pigment where to go, resulting in distinctive 'black points' on the mane, tail, ears, and lower legs.

Bay horses are characterised by a reddish-brown or brown body colour, with these black points. The black areas are sometimes referred to as 'black point coloration' or simply 'black points'. Without these, a horse cannot be considered a bay horse.

The bay colour is incredibly diverse, with numerous breeds of horses exhibiting various shades of bay. These range from copper and sand to a deeper red and mahogany bay dark colour. The standard bay colour is the most common, consisting of a reddish or brown coat with black points.

Some of the other colour variations include:

• Dark Bay Horse or Mahogany Bay Horse: The darkest shade of bay colouring. Often mistaken for seal brown horses, but genetically different.
• Blood Bay Horse: The second darkest colour of bay horses, marked by a deep blood-red coat.
• Copper Bay Horse: A shade brighter than the standard bay, with a rich, orange-red coat.
• Light or Golden Bay Horse: The lightest bay colour variation and the least common. The coat colour can range from a light shade of red to a golden yellow.
• Wild Bay Horse: Almost identical to the standard bay horse, but the black points only extend to the pastern or fetlock of the horse's leg.

Bay horses are commonly seen representing many breeds, although only one breed, the Cleveland Bay, are exclusively this colour. Bay is the most prevalent colour because it is usually the base colour in many horses. This pigment on their hair shaft appears rich, lustrous, and fully saturated, especially when exposed to the sun.

Frequently asked questions