Seal brown (horse)

Last updated
Seal Brown
Vesuvio Bien Vee - Paso Fino Bellas Formas National Champion 3 Year Old Gelding in 2001; photo taken in May of 2006.JPG
A seal brown gelding
VariantsDark bay, brown
Descriptiondark brown body coat with black point coloration and tan coloration around muzzle, eyes, flanks and other "soft" areas. Lacks reddish tint seen in most bay horses
Phenotype
Bodydark brown with lighter tan coloration at soft points of body
Head and LegsBlack
Mane and tailBlack
SkinBlack
EyesBrown
Other notesNot to be confused with pangare

Seal brown is a hair coat color of horses characterized by a near-black body color; with black points, the mane, tail and legs; but also reddish or tan areas around the eyes, muzzle, behind the elbow and in front of the stifle. The term is not to be confused with "brown", which is used by some breed registries to refer to either a seal brown horse or to a dark bay without the additional characteristics of seal brown.

Contents

Like bay, the seal brown color lacks the non-agouti mutation that would create a fully black horse. [1] The genetics behind seal brown are not known, but some think it is caused by an allele of agouti called At. [2] A DNA test said to detect the seal brown (At) allele was developed, but the test was never subjected to peer review and due to unreliable results was subsequently pulled from the market. [3] [4]

The similar dark bay coat color, which also features black points and a dark body, differs from seal brown by the absence of tan markings. Another mimic is the liver chestnut, an all-over dark brown coat including mane and tail, that is sometimes confused with seal brown. However, true seal browns have black points characteristic of all bay horses, while liver chestnuts do not.

Identification

The tan hair around the eyes and muzzle with a very dark body color is typical of seal brown. Kevin Tornado Zlosyn 2005.jpg
The tan hair around the eyes and muzzle with a very dark body color is typical of seal brown.

Opinions vary on what constitutes a true seal brown as distinct from dark bay. In Equine Color Genetics, Dan Phillip Sponenberg wrote "In general, all dark colors with black points that are lighter than black but darker than bay are called brown." [5] In this text, he classifies black-pointed, clear reddish coats of any shade as bay, and black-pointed coats of any shade with black countershading as brown. [6]

Seal brown is best described as a black or nearly-black coat with reddish or tan hairs on the "soft parts": the muzzle, eyes, inner ears, underbelly, behind the elbow, and in front of the stifle. [7] [8] [9] [10] Like other coat colors, seal browns can range in shade. The very darkest are just about black except for their tan areas. Lighter examples are easily confused with dark bays. The mane, tail, and legs are always black. [7]

Terminology

Non-horse people often refer to many horse coat colors as "brown," in particular the bay color. Among horse aficionados, a common assessment is that "...[the term] is only used by people with one horse or with two hundred." [5] The implication is that lay observers will refer to a horse's coat color to be "brown" due to a lack of vocabulary, and those discussing large populations of horses will use "brown" out of a need for a more specific vocabulary. The term "seal brown" is unlikely to be part of a novice's repertoire and is therefore preferable when discussing this specific coat color. This coat color is, illuminatingly, called "black and tan" in some languages. [8]

This horse looks "brown", but the non-black lower legs give him away as a dark liver chestnut. Klacz masci brazowej.JPG
This horse looks "brown", but the non-black lower legs give him away as a dark liver chestnut.

"Brown" but not seal brown

In the most simple terms, the vast majority of horses are indeed some shade of brown, but not "seal brown." Such coat colors include:

Seal browns on paper

Not all breed registries or studbooks recognize seal brown as a distinct coat color. The American Quarter Horse Association and American Paint Horse Association both recognize "brown" as a separate category, while the Arabian Horse Association labels all non-black, black-pointed shades "bay." [11] [12] [13]

Still other registries, such as The Jockey Club which registers Thoroughbreds and Appaloosa Horse Club, offer the designation "dark bay or brown" to cope with the ambiguity in terminology and identification. [9] Among historically German breeds and registries, the term rappe indicates a black horse, braun is bay, while dunkelbraun indicates dark bay and schwarzbraun indicates seal brown (literally black-brown). [14] In France, seal brown horses are recognized among the "black coat family". [15]

The presence of other coat color genes can modify a seal brown coat. The seal brown family includes:

Genetics of seal brown

In rabbits and other species, the black and tan color comes from an allele of the agouti gene called a. State fair 06 029.jpg
In rabbits and other species, the black and tan color comes from an allele of the agouti gene called a.

The genetics behind seal brown are not known.

Since 1951, it has been proposed that seal brown was caused by an allele of the agouti gene, given the name at. [20] This is based on the many other species where similar black-and-tan patterns are caused by alleles at the agouti locus. [2] One genetics lab offered a test for seal brown in 2009, [21] but the underlying studies were not peer-reviewed and the test was pulled from the market due to inconsistent results. [3]

Former theories about the genetics of seal brown

An early version of the currently-accepted equine Agouti gene theory was first presented in 1951 by Miguel Odriozola in A los colores del caballo, subsequently reviewed by William Ernest Castle in Genetics . [22] This theory prevailed until the 1990s, when discoveries of similar conditions in other species provided alternate explanations.

Black and pangaré

For a period, the seal brown phenotype - black or near-black coat with tan or red hairs on the soft areas - was described as a true black coat affected by pangaré , or mealy-factor. [23] Pangaré is a quality common to the Przewalski's horse and so-called primitive horse breeds such as the Exmoor Pony. The trait is characterized by pale hairs, typically off-white to light tan, around the eyes, muzzle, and underside of the body. [24]

These Exmoor ponies may be dark bay or seal brown, but exhibit pangare, which is pale in comparison to the reddish areas on a seal brown. Exmoor Family.jpg
These Exmoor ponies may be dark bay or seal brown, but exhibit pangaré, which is pale in comparison to the reddish areas on a seal brown.

This theory was discarded when the equine Agouti gene (ASIP) was sequenced in 2001, finding that horses fitting the seal brown phenotype did not possess the homozygous recessive a/a Agouti genotype. [1]

Tyrosinase-brown

Tyrosinase-related protein 1 (TYRP1) is a protein involved in melanin synthesis, and is encoded by the TYRP1 gene, also called the brown (b) locus. In humans, mutations in the TYRP1 gene account for variations in "normal" skin, hair and eye coloration, as well as types of clinical Albinism. Mutations in the TYRP1 gene of other mammals result in various reddish-brown coat color phenotypes: Brown in mice, Chocolate in cats, Chocolate in dogs, and Dun in cattle. [25]

The phenotypes associated with TYRP1 mutations are typically rufous or chocolate rather than the black-dominated coats of seal brown horses, and usually result in pinkish-brown skin and light eyes. This is not the case for seal brown horses, and the role of TYRP1 in seal brown was ruled out after it was sequenced in 2001. [1]

Extension-brown and dominant black

The allure of a pure black coat on a horse has struck horse breeders for centuries, resulting in all-black breeds like the Friesian horse. The breeding of pure black horses is attended by two problems: some black coats fade with exposure to light and sweat, and breeding two "black" horses together would sometimes produce non-black horses. In some cases, faded true black horses have lighter coats than the darkest near-black horses. [7]

Faded black horses (a/a), may be mistaken for seal brown or dark bay. Pict2634ka.jpg
Faded black horses (a/a), may be mistaken for seal brown or dark bay.

To account for this, W.E. Castle postulated that there was a third allele at the Extension locus: ED or "dominant black". Based on the existence of such conditions in other animals, Castle suggested that the dominant black gene (ED) would override the "points" pattern of dominant Agouti (A) and produce black or near-black horses, which could then go on to have bay offspring. The implication was that the seal brown coat color, which is often quite nearly black, could be produced by this allele. [26]

Similarly, Sponenberg once hypothesized an Extension-brown (EB) allele, dominant over the wildtype E. He described an allele responsible for black countershading, or sootiness, which would distinguish all shades of brown from all shades of bay.

Both theories were laid to rest after the characterization of the equine MC1R or Extension, which showed no such alleles. [1] However, it remains likely that a genetic control for sootiness does exist.

Dark bay vs. seal brown

Both Dark Bay horses, which have a black mane, tail, and legs with a dark reddish brown or sooty coat, and seal brown horses, which have very dark brown coats in addition to black "points", with reddish or tan hairs around their muzzle, eyes, elbows, and flanks have one of two genotypes at the Agouti locus: A/A or A/a. [27] Both coat colors exhibit a broad range of potential shades due to a variety of factors including the bleaching or fading of black hair, nutrition, and the presence of sooty or countershading factors.

Many black horses fade, sunbleach, or otherwise undergo a lightening of their coat color with exposure to sunlight and sweat. These horses are often mistaken for seal browns or dark bays. Horses which do not undergo such fading are now usually called “non-fading” black, though other terms were used in the past. [28] However, though hypothesized, there does not appear to be a separate “non-fading” allele for black, either. [27] Mineral and vitamin deficiencies can also contribute to a lighter coat, similar to sunbleaching.

Rich red tones, top-down sootiness with dappling, and relatively restricted black points identify this dark bay. Traken.jpg
Rich red tones, top-down sootiness with dappling, and relatively restricted black points identify this dark bay.

Black-pointed horses that are not uniformly black often exhibit a trait called sootiness. A sooty coat exhibits a mixing of black or darker hairs more concentrated on the dorsal aspect (top) of the animal, and less prevalent on the underparts. Sootiness is thought to be a form of countershading. Horses without any sootiness are termed "clear-coated". Sootiness can be minor or quite extensive, and often includes dappling. Dark bay horses are typically sooty. The difference between the top-down distribution of the sooty trait and the lighter soft areas of a seal brown can also be difficult to distinguish from one another. The team of French researchers who developed the DNA test for the recessive a allele also discussed the possibility that Extension might be dosage-dependent. They found a statistically significant tendency for lighter bays to be heterozygous for the dominant, wildtype Extension allele (E/e, also written E+/Ee) while darker bays were more often homozygous (E/E). The authors acknowledged that other factors could play a role, and that the claim needed to be studied on a greater scale. [29] This type of dosage-dependent behavior was not observed with Agouti. [30]

Related Research Articles

<span class="mw-page-title-main">Palomino</span> Genetic color in horses

Palomino is a genetic color in horses, consisting of a gold coat and white mane and tail; the degree of whiteness can vary from bright white to yellow. Genetically, the palomino color is created by a single allele of a dilution gene called the cream gene working on a "red" (chestnut) base coat. Palomino is created by a genetic mechanism of incomplete dominance, hence it is not considered true-breeding. However, most color breed registries that record palomino horses were founded before equine coat color genetics were understood as well as they are today, therefore the standard definition of a palomino is based on the visible coat color, not heritability nor the underlying presence of the dilution gene.

<span class="mw-page-title-main">Dilution gene</span> Gene that lightens the coat colour of certain animals

A dilution gene is any one of a number of genes that act to create a lighter coat color in living creatures. There are many examples of such genes:

<span class="mw-page-title-main">Bay (horse)</span> Hair coat color of horses

Bay is a hair coat color of horses, characterized by a reddish-brown or brown body color with a black point coloration on the mane, tail, ear edges, and lower legs. Bay is one of the most common coat colors in many horse breeds.

<span class="mw-page-title-main">Buckskin (horse)</span> Equine coat color

Buckskin is a hair coat color of horses, referring to a color that resembles certain shades of tanned deerskin. Similar colors in some breeds of dogs are also called buckskin. The horse has a tan or gold colored coat with black points. Buckskin occurs as a result of the cream dilution gene acting on a bay horse. Therefore, a buckskin has the Extension, or "black base coat" (E) gene, the agouti gene (A) gene, which restricts the black base coat to the points, and one copy of the cream gene (CCr), which lightens the red/brown color of the bay coat to a tan/gold.

At right is displayed the color traditionally called liver.

<span class="mw-page-title-main">Point coloration</span> Coloration of animal coat/fur

Point coloration is animal coat coloration with a pale body and relatively darker extremities, i.e. the face, ears, feet, tail, and scrotum. It is most recognized as the coloration of Siamese and related breeds of cat, but can be found in dogs, rabbits, rats, sheep, guinea pigs and horses as well.

<span class="mw-page-title-main">Gray horse</span> Coat color characterized by progressive depigmentation of the colored hairs of the coat

A gray horse has a coat color characterized by progressive depigmentation of the colored hairs of the coat. Most gray horses have black skin and dark eyes; unlike some equine dilution genes and some other genes that lead to depigmentation, gray does not affect skin or eye color. Gray horses may be born any base color, depending on other color genes present. White hairs begin to appear at or shortly after birth and become progressively more prevalent as the horse ages as white hairs become intermingled with hairs of other colors. Graying can occur at different rates—very quickly on one horse and very slowly on another. As adults, most gray horses eventually become completely white, though some retain intermixed light and dark hairs.

<span class="mw-page-title-main">Cream gene</span> Gene responsible for a number of horse coat colors

The cream gene is responsible for a number of horse coat colors. Horses that have the cream gene in addition to a base coat color that is chestnut will become palomino if they are heterozygous, having one copy of the cream gene, or cremello, if they are homozygous. Similarly, horses with a bay base coat and the cream gene will be buckskin or perlino. A black base coat with the cream gene becomes the not-always-recognized smoky black or a smoky cream. Cream horses, even those with blue eyes, are not white horses. Dilution coloring is also not related to any of the white spotting patterns.

<span class="mw-page-title-main">Champagne gene</span> Simple dominant allele responsible for a number of rare horse coat colors

The champagne gene is a simple dominant allele responsible for a number of rare horse coat colors. The most distinctive traits of horses with the champagne gene are the hazel eyes and pinkish, freckled skin, which are bright blue and bright pink at birth, respectively. The coat color is also affected: any hairs that would have been red are gold, and any hairs that would have been black are chocolate brown. If a horse inherits the champagne gene from either or both parents, a coat that would otherwise be chestnut is instead gold champagne, with bay corresponding to amber champagne, seal brown to sable champagne, and black to classic champagne. A horse must have at least one champagne parent to inherit the champagne gene, for which there is now a DNA test.

<span class="mw-page-title-main">Silver dapple gene</span>

The silver or silver dapple (Z) gene is a dilution gene that affects the black base coat color and is associated with Multiple Congenital Ocular Abnormalities. It will typically dilute a black mane and tail to a silvery gray or flaxen color, and a black body to a chocolaty brown, sometimes with dapples. It is responsible for a group of coat colors in horses called "silver dapple" in the west, or "taffy" in Australia. The most common colors in this category are black silver and bay silver, referring to the respective underlying coat color.

<span class="mw-page-title-main">Equine coat color genetics</span> Genetics behind the equine coat color

Equine coat color genetics determine a horse's coat color. Many colors are possible, but all variations are produced by changes in only a few genes.

<span class="mw-page-title-main">Dun gene</span> Dilution gene

The dun gene is a dilution gene that affects both red and black pigments in the coat color of a horse. The dun gene lightens most of the body while leaving the mane, tail, legs, and primitive markings the shade of the undiluted base coat color. A dun horse always has a dark dorsal stripe down the middle of its back, usually has a darker face and legs, and may have transverse striping across the shoulders or horizontal striping on the back of the forelegs. Body color depends on the underlying coat color genetics. A classic "bay dun" is a gray-gold or tan, characterized by a body color ranging from sandy yellow to reddish brown. Duns with a chestnut base may appear a light tan shade, and those with black base coloration are a smoky gray. Manes, tails, primitive markings, and other dark areas are usually the shade of the undiluted base coat color. The dun gene may interact with all other coat color alleles.

<span class="mw-page-title-main">Chestnut (horse color)</span> Horse coat color

Chestnut is a hair coat color of horses consisting of a reddish-to-brown coat with a mane and tail the same or lighter in color than the coat. Chestnut is characterized by the absolute absence of true black hairs. It is one of the most common horse coat colors, seen in almost every breed of horse.

<span class="mw-page-title-main">Equine coat color</span> Horse coat colors and markings

Horses exhibit a diverse array of coat colors and distinctive markings. A specialized vocabulary has evolved to describe them.

<span class="mw-page-title-main">Black horse</span> Horse coat color

Black is a hair coat color of horses in which the entire hair coat is black. Black is a relatively uncommon coat color, and it is not uncommon to mistake dark chestnuts or bays for black.

<span class="mw-page-title-main">Smoky black</span>

Smoky black or just smoky is a hair coat color of horses which appears dark brown to black in color. Smoky black is produced by the action of a heterozygous cream gene on an underlying black coat color. Therefore, smoky black is a member of the cream family of coat color dilutions, and found in horse populations that have other cream-based colors such as palomino, buckskin, perlino, cremello and smoky cream. All smoky blacks must have at least one parent with the cream gene, and a smoky black can only be verified through DNA testing or parentage. Smoky black has been mistaken for faded black, dark bay or brown, grullo or even liver chestnut.

<span class="mw-page-title-main">Sooty (gene)</span> Trait characterized by black or darker hairs mixed into a horses coat

A horse coat color that has the sooty trait is characterized by black or darker hairs mixed into a horse's coat, typically concentrated along the topline of the horse and less prevalent on the underparts. Sootiness is presumed to be an inherited trait, though the precise genetic mechanism, or series of mechanisms, is not well understood.

<span class="mw-page-title-main">Pangaré</span> Coat trait found in some horses

Pangaré is a coat trait found in some horses that features pale hair around the eyes and muzzle and underside of the body. These pale areas can extend up to the flanks, throat and chest, behind the elbows, in front of the stifle, and up the buttock. Animals with the pangaré trait are sometimes called "mealy" or "light-pointed". The color of these lighter areas depends on the underlying color and ranges from off-white to light tan. This type of coloration is most often found in breeds such as the Fjord horse, Exmoor Pony, and Haflinger. Wild equids like the Przewalski's Horse, Onager, African Wild Ass, Kiang as well as the domestic Donkey exhibit pangaré as a rule. Pangaré is thought to be a type of protective countershading. Horse foals are often born with "foal pangaré" or light points, especially over black haired areas, which they lose when they shed their foal coats.

<span class="mw-page-title-main">Flaxen gene</span> Flaxen is a genetic trait that causes a lighter mane and tail than body color of chestnut horses.

Flaxen is a genetic trait in which the mane and tail of chestnut-colored horses are noticeably lighter than the body coat color, often a golden blonde shade. Manes and tails can also be a mixture of darker and lighter hairs. Certain horse breeds such as the Haflinger carry flaxen chestnut coloration as a breed trait. It is seen in chestnut-colored animals of other horse breeds that may not be exclusively chestnut.

The agouti gene, the Agouti-signaling protein (ASIP) is responsible for variations in color in many species. Agouti works with extension to regulate the color of melanin which is produced in hairs. The agouti protein causes red to yellow pheomelanin to be produced, while the competing molecule α-MSH signals production of brown to black eumelanin. In wildtype mice, alternating cycles of agouti and α-MSH production cause agouti coloration. Each hair has bands of yellow which grew during agouti production, and black which grew during α-MSH production. Wildtype mice also have light-colored bellies. The hairs there are a creamy color the whole length because the agouti protein was produced the whole time the hairs were growing.

References

  1. 1 2 3 4 Rieder, Stefan; Sead Taourit; Denis Mariat; Bertrand Langlois; Gérard Guérin (2001). "Mutations in the agouti (ASIP), the extension (MC1R), and the brown (TYRP1) loci and their association to coat color phenotypes in horses (Equus caballus)". Mammalian Genome. Springer-Verlag. 12 (6): 450–455. doi:10.1007/s003350020017. PMID   11353392. S2CID   2012676.
  2. 1 2 Sponenberg, D. Phillip; Bellone, Rebecca (2017). Equine Color Genetics Fourth Edition. Wiley Blackwell. pp. 32, 34. Control for the difference between wild bay and bay most likely resides at the Agouti locus. ... Seal brown is thought to be caused by an Agouti locus allele which is symbolized At for black and tan because alleles with similar action occur in many species, and lead to minor tan areas in the same locations as the seal brown color of horses.
  3. 1 2 "The Enigmatic Brown Horse | Color Genetics".
  4. ↑ "Understanding Equine DNA and Agouti". Archived from the original on August 23, 2014.
  5. 1 2 Sponenberg, Dan Phillip (2003). Equine Color Genetics (2 ed.). Blackwell. ISBN   0-8138-0759-X.
  6. ↑ Sponenberg 2003. pg 25. "As a general rule, better accuracy is achieved by distinguishing brown from bay by the presence of sooty countershading."
  7. 1 2 3 Evans, James Warren; Warren J. Evans; Anthony Borton (1990). The Horse (2 ed.). Macmillan. ISBN   0-7167-1811-1.
  8. 1 2 B. Kostelnik. "Brown". Hippo-Logistics. Archived from the original on November 20, 2021. Retrieved Nov 19, 2021.
  9. 1 2 "Color Guide". The American Stud Book Principal Rules and Requirements. The Jockey Club. Retrieved 2009-03-01. Dark Bay/Brown: The entire coat of the horse will vary from a brown, with areas of tan on the shoulders, head and flanks, to a dark brown, with tan areas seen only in the flanks and/or muzzle. The mane, tail and lower portion of the legs are always black, unless white markings are present.
  10. ↑ "Colors & Markings" (PDF). Tennessee Walking Horse Breeders and Exhibitors Association. Retrieved 2009-03-01. BROWN: The Brown horse's body color is black except for lighter brown areas around the muzzle, eyes, flanks, and insides of the legs.
  11. ↑ "Coat Color Genetics" (PDF). American Quarter Horse Association. Archived from the original (PDF) on 2009-02-06. Retrieved 2009-03-01.
  12. ↑ "Coat Colors". American Paint Horse Association. Archived from the original on 2009-01-22. Retrieved 2009-03-01.
  13. ↑ "What Color Is My Horse?". Arabian Horse Association. Archived from the original on 2008-05-14. Retrieved 2009-03-14.
  14. ↑ "Glossary". Gatewood Farms LLC. Archived from the original on 2008-09-30. Retrieved 2009-03-14.
  15. ↑ "La famille du noir". Archived from the original on August 27, 2012.
  16. ↑ "Buckskin". Morgan Colors. Retrieved 2009-03-15.
  17. ↑ "Sable". Champagne Colors. International Champagne Horse Registry. Retrieved 2009-03-15.
  18. ↑ "Brown/Bay Dun Colors & Markings". Dun Central Station. Archived from the original on March 5, 2009. Retrieved 2009-03-15.
  19. ↑ Letko, A.; Ammann, B.; Jagannathan, V.; Henkel, J.; Leuthard, F.; Schelling, C.; Carneiro, M.; Drögemüller, C.; Leeb, T. (2020). "A deletion spanning the promoter and first exon of the hair cycle-specific ASIP transcript isoform in black and tan rabbits". Animal Genetics. 51 (1): 137–140. doi:10.1111/age.12881. PMID   31729778. S2CID   208034608.
  20. ↑ Castle, W.E.; W.R. Singleton (September 1961). "The Palomino Horse" (PDF). Genetics. 46 (9): 1143–1150. doi:10.1093/genetics/46.9.1143. PMC   1210264 . PMID   13877241. Archived (PDF) from the original on 2008-09-05. Retrieved 2008-03-04.
  21. ↑ "Equine Testing Services". Pet DNA Services of AZ. Archived from the original on 2009-05-22. Retrieved 2009-05-26.
  22. ↑ Castle, WE (1954). "Coat color inheritance in horses and in other mammals" (PDF). Genetics. 39 (1): 35–44. doi:10.1093/genetics/39.1.35. PMC   1209634 . PMID   17247465.
  23. ↑ Sponenberg 2003. pg. 29. "Some horses referred to as brown are essentially black but have the mealy effect superimposed. Such horses are called seal brown. Seal browns and very darkly countershaded browns can look almost identical and illustrate that occasionally it is difficult to assess a horse's genotype accurately by visual inspection of phenotype alone."
  24. ↑ Sponenberg 2003, pg 123. Fig. 9.10. "The mealy effect generally is lighter and more yellow than residual nonblack areas (which tend to be redder) on very sooty horses."
  25. ↑ "*115501 TYROSINASE-RELATED PROTEIN 1; TYRP1". Online Mendelian Inheritance in Man. Johns Hopkins University. 2008-09-05. Retrieved 2009-03-16.
  26. ↑ "Castle postulated that another allele, ED, extends the dark pigment so much that it actually masks the effect of the bay pattern gene, A. He called this the gene for dominant black and described the color as jet black, which does not fade in sunlight as the ordinary black may do. The foal coat is also thought to be black, whereas the first coat of the recessive black is often more of a mouse gray color. The existence of a similar gene in other mammals helped lead him to this conclusion. Thus, ED is thought to extend the dark color even if A or at is present (that is, ED is epistatic to A and at). A jet black could be ED_aa or ED_A_ or ED_atat or ED_ata, where the blank indicates that the paired gene has no effect. There is no direct evidence that the gene ED exists in the horse."
  27. 1 2 Rieder, Stefan (December 2009). "Molecular tests for coat colours in horses". Journal of Animal Breeding and Genetics. 126 (6): 415–424. doi:10.1111/j.1439-0388.2009.00832.x. PMID   19912415.
  28. ↑ Sponenberg 2003, pg 24. "Some black horses never seem to fade in the sunlight and are called jet black or raven black. Others tend to get a rusty tinge during certain times of the year and are then a flatter color, but are still black. In Austria these are called summer black (sommer rappe), which reflects the fact that many black horses fade at least somewhat in the heat and sunlight of summer."
  29. ↑ Rieder et al. 2001, pg 454: A statistically significant tendency (X249.1; p < 0.01) of lighter bay shades carrying the EE/Ee genotype (35 of 42 bay horses) and darker bay shades carrying the EE/EE genotype (9 of 16 dark bay horses) was found in our panel. Thus, lighter bay shades would be at least partially explained by a dosage effect of an average 50% less working melanocortin-1-receptor function due to the Ee-allele (Table 2). However, this result might be biased by the structure of our horse panel and presently unknown genetic variation.
  30. ↑ Rieder et al. 2001, pg 454: We could not find any association between the agouti Aa-allele status (A/Aa versus A/A) and "dark" shaded horses (Table 2). From the 120 horses typed, 34 were heterozygote carriers of the Aaallele. From those, 9 were considered normal bay and 7 dark bay, as well as 7 normal chestnut and 2 dark chestnut. One normal chestnut was found homozygous for the Aa-allele.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.