Bay (horse)
Bay | |
---|---|
agouti gene (A) | |
Description | reddish-brown body coat with black point coloration |
Phenotype | |
Body | Reddish-Brown |
Head and Legs | Black |
Mane and tail | Black |
Skin | Black |
Eyes | Brown, unless modified by another gene |
Other notes | Black ear edges |
Bay is a
The black areas of a bay horse's hair coat are called "black points", and without them, a horse is not a bay horse. Black points may sometimes be covered by white
The addition of dilution genes or various spotting pattern genes create many additional coat colors, although the underlying bay coat color genetics usually manifest by a warm-toned red, tan, or brownish body color and the appearance of black points.
Color variations and terminology
Bay horses range in color from a light copper red, to a rich red blood bay (the best-known variety of bay horse) to a very dark red or brown called dark bay, mahogany bay, black-bay, or brown (or "seal brown"). The dark brown shades of bay are referred to in other languages by words meaning "black-and-tan." Dark bays/browns may be so dark as to have nearly black coats, with brownish-red hairs visible only under the eyes, around the muzzle, behind the elbow, and in front of the stifle. Dark bay should not be confused with
Bay horses have black skin and dark eyes, except for the skin under markings, which is pink. Skin color can help an observer distinguish between a bay horse with white markings and a horse which resembles bay but is not.
The pigment in a bay horse's coat, regardless of shade, is rich and fully saturated. This makes bays particularly lustrous in the sun if properly cared for. Some bay horses exhibit dappling, which is caused by textured, concentric rings within the coat. Dapples on a bay horse suggest good condition and care, though many well-cared for horses never dapple. The tendency to dapple may also be, to some extent, genetic.
The red areas of a bay coat usually have a two-toned hair shaft, which, if shaved closely (such as when body-clipping for a
There are many terms that are used to describe particular shades and qualities of a bay coat. Some shade variations can be related to nutrition and grooming, but most appear to be caused by inherited factors not yet fully understood.
The shades with the least amount of point coloration are called wild bays. Wild bays are true bays with fully pigmented reddish coat color and black manes and tails, but the black points only extend up to the
Some breed registries use the term "brown" to describe darker bays, though modern genetics have resulted in some terminology revisions such as the use of "bay or brown." However, "liver"
To further complicate matters, there apparently exists more than one genetic mechanism that darkens coat colors. One is a theorized
Effect of gray gene
Some
Colors confused with bay
- Chestnuts, sometimes called "Sorrels", have a reddish body coat similar to a bay, but no black points. Their legs and ear edges are the same color as the rest of their body (unless they have white markings) and their manes and tails are the same shade as their body color or even a few shades lighter.
- Blackis occasionally confused with dark bays and liver chestnuts because some black horses "sunburn", that is, when kept out in the sun, they develop a bleached-out coat that looks brownish, particularly in the fine-haired areas around the flanks. However, a true black can be recognized by looking at the fine hairs around the muzzle and eyes. These hairs are always black on a black horse, but are reddish, brownish, or even a light gold on a bay or chestnut.
Genetics
The bay color is created with two colors of
At agouti, the dominant, ancestral A allele limits the location of black pigment to the points, seen in the bay color. The recessive a allele allows black pigment to cover the whole body, resulting in a fully black horse.[4]
At extension, horses with the dominant,
The extent to which a bay passes on its color varies. Two bay horses heterozygous for E (Ee x Ee) have a 25% statistical probability to produce a chestnut. Similarly, bay horses heterozygous for A (Aa x Aa) may produce a black foal.
Because chestnut's e at extension is recessive to bay's E, two chestnut horses can never have a bay foal. Likewise, because black's a at agouti is recessive, two black horses cannot have a bay foal either. However, it is possible for a chestnut horse and a black horse to produce a bay foal, if the chestnut horse is AA or Aa at agouti. The foal can inherit the A allele from its chestnut parent and the E allele from its black parent, resulting in a bay color.
The genetics behind the different shades of bay are still under investigation. A genome wide association study identified a region of equine chromosome 22 that appears to correlate with the extent of black pigment on bay horses. This region includes the 5' end of the agouti gene as well as another gene called RALY, both known to affect coat color in other species. Further research is needed to pinpoint the causative mutation.[6]
Origin
The oldest known horse coat color is bay dun, a tan color with a black mane, tail, dorsal stripe, and lower legs. The legs may sometimes have zebra-like black stripes; these, along with the dorsal stripe seen on all dun horses, are called primitive markings. Over 42,000 years ago, a mutation called non-dun 1 appeared, which allowed horses to be bay. Non-dun 1 replaces the tan dun color with the darker brown of bay, but keeps the primitive markings seen on dun. Later a second mutation to the dun gene, called non-dun 2, was able to remove the primitive markings altogether to create the non-striped bay color common today.[7][8]
Bay-family colors
The effects of additional equine coat color genes on a bay template alter the basic color into other shades or patterns:
- heterozygousfor the dominant creme (CCr) allele. The black pigment remains largely unchanged, but any red pigment in the coat is diluted to gold. Buckskins are seldom mistaken for bays because their coats are significantly lighter and have no hint of a red or orange tint.
- homozygousfor the dominant creme (CCr) allele. Both black and red pigment are diluted to some shade of creme, though the formerly black points often have a stronger reddish cast. The skin is a slightly pigmented pink and the eyes are blue.
- dominant dun allele. Red and black pigment at the extremities remains largely unchanged, but on the body, black pigment is diluted to slate and red pigment is diluted to a dustier shade. The effect is similar to buckskin, but the coat of a bay dun is a flatter tan rather than bronze, and all duns have some form of primitive markingsthat include a dorsal stripe along the backbone, and sometimes faint horizontal striping at the back of the front legs.
- Amber champagne refers to a bay horse with at least one dominant champagne allele. Black pigment is diluted to warm brown and red pigment to gold. The effect is similar to buckskin, but the points of an amber champagne do not remain black, and the skin is mottled. Amber champagnes also have hazel eyes rather than brown.
- Silver bays are bay horses with at least one dominant silver (Z) allele. Red pigment is unaffected, but black pigment in the short coat is diluted to dark, flat, brown-gray while the longer hairs are diluted to silver. The overall effect on a bay is that of a chocolate-colored horse with a pale mane and tail.
- Bay Roan horses are bays with at least one dominant roan (Rn) allele. The roan gene creates an effect of white hairs intermingled with the red body coat. This color was formerly lumped together with chestnut or "strawberry" roans and called "red roan."
- tricolor" is used, especially in the UK, to refer to bay pintos.
- breed registriesthat do not have a category for pinto.
- Bay Leopards are horses that carry the leopard (Lp) gene or gene complex characteristic of the Appaloosa and other breeds. This gene also produces secondary characteristics that include mottled skin, a white sclera around the eye, and striped hooves.
- A few bay horses may carry the rabicano gene, which either produces faint roaning on only some parts of the body or can cause some white or cream hairs to appear in the mane or tail, sometimes creating a "skunk" effect. Most bays with rabicano are registered as either bays or as bay roans.
See also
References
- ISBN 0-8138-0759-X.
- ^ "The Enigmatic Brown Horse - Color Genetics". Archived from the original on 2016-04-08.
- ^ Understanding Equine DNA and Agouti, at PetDNAServicesAZ; via archive.org; archived February 27, 2015
- ^ "Agouti (Bay/Black)". UC Davis Veterinary Genetics Laboratory. Retrieved Nov 20, 2021.
- ^ "Red Factor". UC Davis Veterinary Genetics Laboratory. Retrieved Nov 20, 2021.
- PMID 32486210.
- PMID 26691985.
- "A horse of a different color: Genetics of camouflage and the dun pattern". ScienceDaily (Press release). December 21, 2015.
- PMID 19390039.
- "Introduction to Coat Color Genetics" from Veterinary Genetics Laboratory, School of Veterinary Medicine, University of California, Davis. Web Site accessed January 12, 2008