Base Color Every horse has a base color, which can be black, bay, or red.
This is controlled by the Extension (Red/Black Factor) and Agouti genes.
The Extension gene controls the production of black or red pigment through out the coat.
The allele for black color (E) is dominant over the red allele (e),
so a horse only needs one copy of the black allele to appear black-based.
The Agouti gene can then modify black pigment by pushing it the the points of the horse, creating a bay.
The Agouti gene is dominant,
so a black pigmented horse only needs one copy of the Agouti gene (A) to appear bay.
Agouti does not have any effect on red pigment.
There may be some variation in the intensity of the base colors,
for example, dark bays compared to light bays, or liver chestnuts to sorrels.
This could be caused by a variation in the expression of the genes or interaction of other genetic factors.
This is controlled by the Extension (Red/Black Factor) and Agouti genes.
The Extension gene controls the production of black or red pigment through out the coat.
The allele for black color (E) is dominant over the red allele (e),
so a horse only needs one copy of the black allele to appear black-based.
The Agouti gene can then modify black pigment by pushing it the the points of the horse, creating a bay.
The Agouti gene is dominant,
so a black pigmented horse only needs one copy of the Agouti gene (A) to appear bay.
Agouti does not have any effect on red pigment.
There may be some variation in the intensity of the base colors,
for example, dark bays compared to light bays, or liver chestnuts to sorrels.
This could be caused by a variation in the expression of the genes or interaction of other genetic factors.
Horse Base Coat Red/Black Factor Agouti
Solid Black EE or Ee aa
Bay or Brown EE or Ee AA or Aa
Red (Chestnut/Sorrel) ee AA, Aa, or aa
Dilutions:
The rest of the color genes act as modifiers on the base coat of the horse.
There are several genes that dilute the color of the horse, including Cream, Pearl, Champagne, Silver, and Dun. While these genes all function to dilute pigment, they are not all expressed in the same manner. The Dun and Champagne genes are dominant, as is Silver, although Silver does not affected red pigment. The Cream gene is incompletely dominant, meaning you will see different effects with the number of Cream genes present, and the Pearl Gene is recessive.
The Cream and Pearl genes do have additive effects, so color testing can be an important tool to determine the correct color of a horse and what it may be able to pass on.
The Grey gene causes a horse to 'grey out' over time, and is dominant, although homozygous horses tend to grey out faster. It is thought that there are other color modifiers, such as Flaxen or Sooty, but the genetic basis to these colors have not yet been determined.
Dilution Gene Mode of Inheritance
Champagne Dominant
Cream Incomplete Dominant
Dun Dominant
Pearl Recessive *Additive Effect with Cream
Silver Dominant *No effect on red pigment
Pattern Gene Mode of Inheritance
Grey Dominant
Equine Base Coat Red/Black Factor
Description: Equine coat color is built on one of two possible base pigments: red or black.
The extension gene controls the production of this base pigment (red or black).
All of the coat colors we see today, from white to black, sorrel to grey - every single one of them begins with either a red or black base pigment.
All horses will have the genetics for black or red pigment, regardless of their physical appearance.
There are a number of dilutions patterns and modifiers which a horse can carry that affect the base pigment of a horse.
Horses that are bay, black, grullo, buckskin, black/blue roan, etc. are black pigmented horses that carry at least one copy of the Black Factor (E) allele.
The black (E) allele of the extension gene is dominant and causes a black pigmented base both in the heterozygous (Ee) and homozygous (EE) state. (the skin is black.)
A horse that is heterozygous for Red/Black Factor means that it carries one copy of the black allele (E) and one copy of the red allele (e).
A horse that is heterozygous for red/black factor can pass on either red or black pigment to its foals. and only one, not bouth.
A homozygous black (EE) horse means that it carries two copies of the black allele (EE). A homozygous black horse will always produce black based foals regardless of its mate.
Horses that are chestnut or sorrel, palomino, red dun, red roan, etc. are red pigmented horses and must carry two copies of the Red Factor (e) allele.
The red (e) allele of the Extension gene is recessive and will only cause red pigmentation when the horse carries two copies of this allele; this is referred to as Homozygous red (ee). (red horses)
Therefore, a red based foal results when both parenst have passed on a copy of the red (e) allele.
Test Results: Animal Genetics offers DNA testing for the extention gene effecting the Red / Black base coat color of a horse. The genetic test verifies the base coat color and presents results as one of the following.
E/E
BlackOnly the black factor detected. The horse tested homozygous for black pigment. It cannot have red foals regardless of the color of the mate. The basic color of the horse will be black, bay or brown unless modified by other color modifying genes.
E/e
BlackBoth black and red factors detected. The horse tested heterozygous for the red factor. It can transmit either E or e to its offspring. The basic color of the horse will be black, bay or brown unless modified by other color modifying genes.
e/e
RedOnly the red factor detected. The horse tested homozygous for red pigment. The basic color is chestnut or sorrel unless modified by other color modifying genes.
Champagne Dilution
The Champagne dilution gene lightens a horse's coat color by diluting the pigment.
The specific color produced will depend on the horse's base color --
black coats can lighten to a dark brown,
chestnut coats to an apricot or gold,'
and bay coats to a golden brown.
A horse can carry more than one dilution gene which can further affect coat color.
Although similar to the cream, pearl and dun dilutions, the Champagne gene has certain characteristics that distinguish it from other dilutions.
Common characteristics of a Champagne horse include pinkish freckled or mottled skin, a shiny coat that is often slightly darker in the winter, and a hazel (light brown) or amber (green/yellow)eye color.
Champagne horses are typically born with a blue eye color that evolves to a hazel or an amber color and pink skin that becomes darker and more freckled over time, especially around the eyes and muzzle.
Champagne has been documented in the Quarter Horse, Andalusien (PRE), Lusitano (PSL), Tennessee Walker, American Saddlebred, Missouri Fox Trotter, Miniature Horses and several other breeds.
Base color Interaction of Champagne Dilution:
Classic champagnes would be homozygous for the recessive allele Aa, for which a test has recently been developed.
Classic champagne: Uniform black horses (excluding bay) are diluted to classic champagne.
This involves the lightening of all body pigmentation to a pale-black color. Classic champagne horses are champagne horses with a black base color (the color is sometimes also called champagne black). The coat is diluted to a very attractive lilac tan or pale smokey brown color, with the points being a darker version of the same color.
The eyes are blue at birth but change to hazel or amber by about 3 months if the horse has 2 champange genes, if the horse have only 1 champange gene, the horses eye color will change slow or only 50%, so the horse looks like it has blue eyes whit yellow og grenish reflections, it will still get frinkles but not in the big therme. Classic champagne horses are sometimes mistaken for buckskins or grullas (black dun).
They are also sometimes called "lilac dun".
They are, however genetically distinct from these, and the cream (CCr) and dun(DD) genes are not present. There are no primitive marks (such as dorsal stripes and leg barrings) as there are on dun horses. The pink skin and amber or hazel eyes also distinguish classic champagnes from these other dilute colors.
It seems likely that the suggested existence of a separate chocolate brown color was due to the observation of classic champagne, rather than to the existence of allele Bb at the brown locus.
Gold champagne: chestnut/sorrel based horses are diluted to gold. Full coat modification occurs leading to uniform dilution of the body. Additionally, the gold horse will often have a flaxen mane and tail.
(OBS: Gold champagne horses are visually similar to chestnut-based horses modified by the cream gene (Palominos). Champagne horses with a chestnut base color are called gold champagne. Gold champagne horses resemble palominos, having a golden color coat. They may have a white mane & tail, or these may be gold colored too. Probably this depends on whether the flaxen gene is also present, but I don’t think this has been properly tested yet.
Gold champagnes are often referred to as pink, pumpkin or wheaten skinned palominos and usually registered as palomino. Sometimes their coat has a pinkish hue not normally seen in palominos. However the resemblance to palomino is purely in the phenotype (external appearance) as they do not have the cream dilution allele (CCr).
Ivory Champange: In combination with palomino champagne makes gold cream, "Ivory" champagne was the name originally used for the combination of chestnut, champagne and cream (gold champagne with a cream gene, or you could say a palomino with a champagne gene!). so insted the name was used for dobbelt delution cream genes in champange, so Such horses have an ivory-colored body with a white mane & tail, resembling cremellos but with amber eyes. Thise are born loking like cremello´s, then change in to Palomino whit blue eyes and turns back to ivory collored horses. The eye collor in horses whit only one champange gene, can change all out to fully green or only some of the way.
Sabel Champange: Sable champagne horses are champagne horses with a brown base color. The coat color is between amber champagne and classic champagne, but resembling classic more than amber, and often with more shading than either.
If it is not clear from the phenotype and pedigree sable champagne could be distinguished from classic champagne by genetic testing at the agouti locus. Classic champagnes would be homozygous for the recessive allele Aa, for which a test has recently been developed.
Sable champagne horses are sometimes mistaken for buckskins or duns. They are, however genetically and phenotypically distinct from both of these, and the cream (CCr) and dun(DD) genes are not present. There are no primitive marks (such as dorsal stripes and leg barrings) as there are on dun horses. The pink skin and amber or hazel eyes also distinguish sable champagnes from these other dilute colors. They also have pink skin with freckles. Their eyes are blue or whitish at birth and turn to amber or hazel after about three months. Sable champagne used to be called buckskin champagne, but this name does rather encourage confusion with true buckskins, which sable champagnes are not.
Amber champagne: Bay horses carrying champagne dilution are designated amber.
Unlike coat dilutions that only work upon black pigment, the champagne will dilute the whole coat of the bay horse.
(OBS:Amber champagnes are sometimes referred to as amber buckskins.)Horses with a bay base coat are amber champagne, and those with a brown base coat are sable champagne.
Dun Champange: Like Cream and champange kan inflickt on one an other, the Dun gen and the champange gene can do the same. in thise cases, you have a Champange Dun. the horse then be Dun whit all the dun carestica, stripes, ell ect. but have the champange gene infleckt the color .
Champagne dilution is caused by a dominant gene, meaning that a horse with a single copy of the Champagne gene will have Champagne characteristics.
(OBS: Unlike cream dilution, there are no visual differences between a horse with one copy or two copies of Champagne. the horse will be champange no matter what,)
A homozygous Champagne horse will always pass one copy of the Champagne gene to its foal. (the Foal WILL be delutet champange no matter the base color.)the foal WILL be fadet when born and all the caracteristic will show.The eyes are blue at birth but change to hazel or amber by about 3 months if the horse has 2 champange genes.
Heterozygous horses have a 50% chance of passing the gene on to its foals. 50/50 change for champange. the coate color will fade over time, but eyes, freckled or mottled skin, a shiny coat may not show. when the horse have only 1 champange gene, the horses eye color will change slow or only 50%, so the horse looks like it has blue eyes whit yellow og grenish reflections, it will still get frinkles but not in the big therme. often they will get brown spots in the eyes, thats courst by the frinkle effect.
Theres ALOT more Champagne vertions then named here. Ivory Champange, golden champange and Dun champange ect. These er the 3 most common!
The champagne color dilution gene exists in two forms: CHc, the Champagne dilution allele is dominant over the wildtype allele CH+. Therefore Dominant champagne horses can be either of genotype CHcCHc or CHc CH+. The CHc allele dilutes red to a golden color, and black to a brown or taupe color.
OBS: the champange test will only show Dominant Champange, this mening that on of the parents have to be homozygot champange, and not Hetrozygot. if the parent is caring only 1 champange gene, the offspring will carry it to, but it will not show on a test for the offspring of a Hetrozygot parent, becaurse it´s a secont generation of 1 genes, so to get it confirmed, the offspring will have to breed whit a homozygot champange and make a Homozygot champange offspring to clame the gen in its gen pool.....until a better test is developt. the test will only show homozygot champange an the 1. generations hetrozygot horses.
Ch/Ch
ChampagnePositive for dominant champagne gene, possessing two inherited copies. Coat will be diluted accordingly. Will pass champagne gene to all foals regardless of mate.
n/Ch
ChampagnePositive for dominant champagne gene, possessing one inherited copy. Coat will be diluted accordingly. Will pass champagne gene to approximately 50% of foals when bred.
n/n
NegativeNon-champagne horse.
Cream Dilution
The cream dilution gene affects both red and black pigment and is responsible for 'diluting' the carrying horse to lighter coat shades and colors.
In many breeds this is often considered a highly desirable trait.
Cream dilution is the gene responsible for palominos, buckskins, cremellos and many more (see below chart).
Horses which carry one copy of the cream gene are identified as single dilutes;
they are heterozygous for the cream dilution gene. (Palominos ect.)
In the simplest case, a bay horse with a single copy of cream is known as a buckskin (OBS: A buckskin, is NOT the name of a brown horse, )
a single dilute black horse is known as a smoky black and a single dilute chestnut or sorrel horse is known as a palomino.
Single dilute horses have a 50% chance on passing the cream gene on to its offspring.
Horses which carry two copies of the cream gene are referred to as double dilutes;
they are homozygous for the cream dilution gene.
A bay (brown) horse with two copies of cream is known as a perlino.
A black horse with two copies of cream is known as a smoky cream
and a chestnut or sorrel (red) horse that carries two copies of cream is known as a cremello.
Double dilute horses will always pass on a copy of the cream gene to its foals.
Cream dilution is caused by a gene mutation (in this case an SNP) in exon 2 of the MATP gene, and subsequently a genetic test has been developed that tests for the presence of this mutation. OBS: There are other genes that may have an effect similar to cream dilution but will not be detected by this test.
The effects that these doses have on the horse's base coloring are outlined as follows:
No Dilution (nn) Single Dilute (nCr) Double Dilute (CrCr)
Chestnut or Sorrel(red) -> Palomino -> Cremello
Bay (brown) -> Buckskin -> Perlino
Black -> Smoky Black -> Smoky Cream
Dun Dilution
The Dun gene is a dilution gene that affects both red and black coat color pigments.
The gene is associated with "primitive marking" (leg stripes, and dark dunkey markings over the shulders) and has the ability to affect the appearance of all black, bay, or chestnut ("red")-based horses to some degree by lightening the base body coat.
The dark stripe down the middle of the animal's back is the most recognizable marking associated with Dun horses.
Other markings include a tail and mane darker than the body coat and usually darker faces and legs, Stripes on the legs is a Dun carataristica, if the horses legs are wery black in a high level of the leg, the propertly cant be seen, another color do´s look lige Dun but isent, a dun horse always have zebra stribes on the legs and schulder stripe.
The classic Dun is a gray-gold or tan, characterized by a body color ranging from sandy yellow to reddish-brown.
Depending on other underlying genetic coat color factors, a Dun horse may appear a light yellowish shade or a steel gray.
Manes, tails, primitive markings(leg stripes) and other dark areas are usually the shade of the non-diluted base coat color.
The Dun allele is dominant, meaning that a horse that carries either a single copy (heterozygous) or two copies (homozygous) of the gene will exhibit a dun phenotype.
Unlike the silver dilution gene (which affects only black-based coats), the Dun gene affects both black and red-based horses.
The Dun dilution gene is characterized by markings which are darker than the body color. These markings include:
- The Dorsal stripe (stripe down the center of the back, along the spine), seen almost universally on all duns.
- Horizontal striping on the back of forelegs, common on most duns, though at times rather faint.
- Shoulder blade striping, the least commonly-seen of the primitive markings.
Base Coat Common Coat color
Red (chestnut base -> + Dun gene-> Red dun
Black base -> + Dun gene-> Blue dun, mouse dun or Grullo/Grulla.
Bay (black base + Agouti gene)-> + Dun gene-> Classic dun, sometimes called "Bay dun" or "Zebra dun"
>-codes-<
D/D
HomozygousHorse will always produce a Dun foal
D/d
HeterozygousHorse tested Heterozygous for Dun and will pass the Dun gene on to its offspring 50%
d/d
Negative Non Dun
Pearl Dilution
Pearl is a coat dilution modifier.
One of the most recent equine color genes to be mapped for commercial genetic testing, it has only been confirmed in a few breeds and is generally considered to be one of the rarer of all color traits.
The presence of the pearl gene has been confirmed in breeds of Iberian origin, such as the Lusitano and Purebred Spanish horse, and it is theorised to be present in the Spanish Mustang.
Where found to be present in the American Quarter horse, Tennasy walking horses and the Akhel tekin horse.
Pearl dilution is regularly referred to as the 'Barlink Factor' in quarter horses.
Pearl dilution is a recessive gene, and therefore will only affect the coat of the carrying horse if:
1) Two inherited copies of the gene are present.
Horses carrying two copies of pearl will have a lightened coat, mane and tail, in addition to bright eye colors due to pigment changes caused by the gene.
2) The cream dilution gene is also present in the pearl-carrying horse.
It has been confirmed that the dominant cream gene will activate the pearl phenotype if the two genes are present.
Horses positive for both cream and pearl will exhibit a double-dilute phenotype, again with a highly pale coat color similar to that of horses that are homozygous for the cream gene.
Pearl dilution will not act if a horse is heterozygous for the trait but negative for the cream dilution gene, meaning that a single inherited copy of the pearl gene alone will not affect the carrier's phenotype.
Heterozygous pearl horses may breed diluted offspring if bred to another pearl carrier or a cream dilute horse.
The visual coat color changes caused by pearl dilution are based upon the foundation color of the horse - for example, the phenotype of a double-pearl bay will vary from the phenotype of a double pearl chestnut.
Prl/Prl
Homozygous
Horse is positive for pearl, and carries two inherited copies of the gene. The phenotype of the homozygous pearl horse will be of dilute appearance, regardless of the presence of cream dilution. The homozygous pearl specimen will pass the pearl gene to 100% of foals, but may only produce diluted offspring if bred to another pearl or cream carrier.
n/Prl
Heterozygous
Horse is positive for pearl, having inherited the trait from one parent.
No visual change to carrying horse, except for in the additional presence of the cream dilution gene. The horse will pass the pearl dilution gene to approximately half of foals when bred.
n/n
NegativeHorse can be considered a non-carrier of the pearl gene.
Silver Dilution
Silver Dilution is a dominant trait, so in order to inherit the trait, a horse requires only one parent to carry and pass on the gene.
Some what similar to the agouti gene, the silver dilution gene will only alter black pigmented horses (Ee or EE) and has no effect on red pigmented horses (ee).
The agouti gene alters the coat by controlling distribution of the black pigment whereas the silver dilution gene does so by diluting areas of black pigment.
The effects of the silver dilution gene can vary greatly.
Dilution by the silver gene on a horse with a uniform black base typically involves lightening of the mane and tail and a dilution of the body to a chocolate color, often dappled as well.
A Bay horse carrying the Silver gene will usually have a lightened mane and tail, as well as lightened lower legs.
It is important to know that although a red horse will not be diluted by the silver gene, it can be a carrier of the gene and thus potentially pass the gene on to its offspring, (calt flaxen red).
Silver dilution has been identified in a number of horse breeds including the Quarter horse, the Rocky Mountain horse, the Icelandic horse, Morgans, Shetland ponies and the Miniature horse. spanish, lusitanos and some warmbloods.
Z/Z
HomozygousHorse tested homozygous for silver dilution (Two copies of the silver allele detected). Black-based horses will have a chocolate body with flaxen mane and tail.
Bay-based horses will have lightened lower legs and flaxen mane and tail.
n/Z
HeterozygousHorse tested heterozygous for silver dilution (One copy of the silver allele detected). Black-based horses will have a chocolate body with flaxen mane and tail.
Bay-based horses will have lightened lower legs and flaxen mane and tail.
n/n
Negativen/n - Negative: horse tested negative for silver dilution.
.
Quarter Horse Colors
Grunden til at tage Quarter horses farver med er at der er mange teorier om at quarteren har farver som ikke ses ved andre racer, dette er dog ikke helt sandt, da de har arvede deres farver fra de spanske heste i tidernes morgen og derfor ikke har eneret på generne.
Grunden til at folk ofte bliver forvirret af feks champange og Pearl farverne som flere gør eneret på, feks quarterhorse og tennese walking horse. begge har dog spanske gener og har arvede farverne igennem der, ligesom mange andre racer med spansk blod.
da spaniolerne i sin tid ikke avlede ud fra farve er farverne gået tabt og så generne så minimale at under 30% stadig har generne( idag er farveavl i de spanske dog meget udbredt), det samme gælder for Dun genet, men til forskel er dun genet båret af langt flere heste end man skulle tro og dukker derfor oftere op, dette er også årsag til at Champange genet v portugisiske heste kaldes for uddød, alene af den grund at så få heste er indehaver af genet, det er dog igennem farveavl og tilfælde blevet genopdaget hos de spanske og bliver nu avlet spicifikt efter for at fremme genet igen,Det kan komme de portugisiske lusitanoer til gode med tiden, indtil videre regnes det dog stadig for uddød og som nævnt tidligere er det derfor en go ide at teste evt champange heste ved specialister inden for feltet, som feks de der spicialisere sig i Quarter horse farver og der igennem få et sikkert resultat.
Derfor nævnes også Quarter horse genetikken her, da de i mange år har avlet farve avl og man derfor vil ku trække både viden og "aaahaaa" viden fra netop disse. Det er nemlig ikke alle steder der er lige spicialiseret i farveavl og fortyndings farver og feks ved racer som Shetlænder og quarter er det muligt at gå endnu længere end til at teste for genet, men også få den spicifikke nuance kode af selve farver som cream, pearl, champange dun osv er indehavere af.
Husk dog altid at både farve navne og genkoder er forskelllige for samme farver og koder alt efter hvor i verden man tester og hos hvem, det er derfor altid godt at skrive koderne ned og undersøge hvilke der er tale om inden for eget regime, eller man kan vælge at ha hele koden, eller alle koderne under hinanden således at alle uanset racer og land kan se hvad genkoderne er på deres eget "farvesprog" om man så vil.
Grunden til at folk ofte bliver forvirret af feks champange og Pearl farverne som flere gør eneret på, feks quarterhorse og tennese walking horse. begge har dog spanske gener og har arvede farverne igennem der, ligesom mange andre racer med spansk blod.
da spaniolerne i sin tid ikke avlede ud fra farve er farverne gået tabt og så generne så minimale at under 30% stadig har generne( idag er farveavl i de spanske dog meget udbredt), det samme gælder for Dun genet, men til forskel er dun genet båret af langt flere heste end man skulle tro og dukker derfor oftere op, dette er også årsag til at Champange genet v portugisiske heste kaldes for uddød, alene af den grund at så få heste er indehaver af genet, det er dog igennem farveavl og tilfælde blevet genopdaget hos de spanske og bliver nu avlet spicifikt efter for at fremme genet igen,Det kan komme de portugisiske lusitanoer til gode med tiden, indtil videre regnes det dog stadig for uddød og som nævnt tidligere er det derfor en go ide at teste evt champange heste ved specialister inden for feltet, som feks de der spicialisere sig i Quarter horse farver og der igennem få et sikkert resultat.
Derfor nævnes også Quarter horse genetikken her, da de i mange år har avlet farve avl og man derfor vil ku trække både viden og "aaahaaa" viden fra netop disse. Det er nemlig ikke alle steder der er lige spicialiseret i farveavl og fortyndings farver og feks ved racer som Shetlænder og quarter er det muligt at gå endnu længere end til at teste for genet, men også få den spicifikke nuance kode af selve farver som cream, pearl, champange dun osv er indehavere af.
Husk dog altid at både farve navne og genkoder er forskelllige for samme farver og koder alt efter hvor i verden man tester og hos hvem, det er derfor altid godt at skrive koderne ned og undersøge hvilke der er tale om inden for eget regime, eller man kan vælge at ha hele koden, eller alle koderne under hinanden således at alle uanset racer og land kan se hvad genkoderne er på deres eget "farvesprog" om man så vil.
A discussion of quarter horse colors - real and registrable.
Until recently there were just 13 accepted quarter horse colors recognized by the American Quarter Horse Association, even though horses of pure-bred quarter horse origin actually occurred in other colors. Those accepted quarter horses colors were sorrel, chestnut, bay, black, brown, gray dun, red dun, grullo, buckskin, palomino, red roan and blue roan. An interesting mix that was decided when little was known about horse genetics!
The predominant quarter horse colors are reported to be sorrel and chestnut (according to their frequency among registered horses). It is interesting that these two colors are listed separately since sorrel horses are actually light chestnut. The use of two terms sometimes creates confusion. I’ve heard the term sorrel used interchangeably with chestnut, with people describing darker chestnut horses as sorrel. In some countries, such as the UK, many horsey people haven’t even have heard of the term sorrel in connection with horses!
Dun, red dun and grullo are distinguished as separate quarter horse colors, although they are all caused by the dun factor gene. Red dun is usually reserved for duns with a chestnut (or sorrel!) base coat, while grullo is the term for a dun with a black base coat. Presumably dun is used for any other combination, notably those with bay or brown base coats.
Buckskins and palominos are horses with a single copy of the cream gene. The first have either bay or brown base coats, but smoky blacks were also registered as buckskins. Palominos have a chestnut (or sorrel!) base coat. Until recently double cream dilutes weren't registrable as pure-bred quarter horses, even if their parents were both 100% quarter horses of 100% foundation breeding!
The double dilutes include cremellos, perlino, and smoky cream which are now accepted quarter horse colors (hooray!).
New dilution genes are now being recognised. The champagne colors occur naturally among quarter horses, with their hazel or greenish eyes and their freckles. Some of these are registered as palomino, or as other cream dilutes, although more and more people recognise the champagne colors as being separate from the cream colors.
The silver dapple (or Taffy) gene does occur very rarely in quarter horses and I predict it will increase in frequency as people become interested in this lovely new (quarter horse) color. Probably there are more American Quarter horses with the silver gene than is currently realised, with some horses being mis-identified, either genuinely or for registration purposes! Also since the gene barely shows itself on red horses there may also be unidentified carriers too.
AQHA set forth strict rules regarding white markings, which should be limited on the face and below the knees. This was despite the fact that foals born of pure-bred parents frequently broke the rule!
Even now the registration certificates of such horses must bear the words: "This horse has white markings designated under AQHA rules as an undesirable trait and uncharacteristic of the breed”. But for one or two alleles in about 60,000 (0.0017-0.0033%) these horses are the same as any other quarter horses and may well have a more ideal conformation and temperament than some solid quarter horses. The money invested to produce them is usually high and their owners are rightly proud them - regardless of their “excessive” white – and they want to show and breed from them.
It seems rather sad that Quarter Horse breeders who get “spotless paint horses”, and paint breeders who get solid foals, have to feel their otherwise quality horses are considered “second class” or unwelcome by some members of both AQHA and the APHA. (And I’m not speaking here as a disgruntled breeder, just as an observer of a peculiar, artificial, and – in my opinion silly – situation!). Another consequence of selecting for minimal white markings is that it occassionally results in foals with the fatal lethal white overo syndrome. The overo spotting pattern is phenotypically heterogeneous and minimally marked horses may show insufficient pattern to be identified as overo horses, even though they have the overo genotype. The AQHA rule will undoubtedly have caused selection for minimally marked overo horses.
Unsurprisingly there are cases of quarter horses having sired or produced lethal white foals, even though they don’t obviously carry the overo gene (i.e. because they have minimal patterning). Not so long ago a somewhat worried lady emailed me alerting me to such a problem. Her stallion – who is without noticeable overo body spotting patterns - had nevertheless been shown to have the overo gene (by molecular testing). Unfortunately he’d already been bred to a couple of mares who also have overo. One only hopes she had a good outcome.
It is clear that quarter horse colors aren't set forever in stone. As more is known so the AQHA rules on quarter horse colors (eventually) change. And when it comes to actual quarter horses, they don't always seem to read the rules. They may well have ideas other than those of the AQHA authorities.
The predominant quarter horse colors are reported to be sorrel and chestnut (according to their frequency among registered horses). It is interesting that these two colors are listed separately since sorrel horses are actually light chestnut. The use of two terms sometimes creates confusion. I’ve heard the term sorrel used interchangeably with chestnut, with people describing darker chestnut horses as sorrel. In some countries, such as the UK, many horsey people haven’t even have heard of the term sorrel in connection with horses!
Dun, red dun and grullo are distinguished as separate quarter horse colors, although they are all caused by the dun factor gene. Red dun is usually reserved for duns with a chestnut (or sorrel!) base coat, while grullo is the term for a dun with a black base coat. Presumably dun is used for any other combination, notably those with bay or brown base coats.
Buckskins and palominos are horses with a single copy of the cream gene. The first have either bay or brown base coats, but smoky blacks were also registered as buckskins. Palominos have a chestnut (or sorrel!) base coat. Until recently double cream dilutes weren't registrable as pure-bred quarter horses, even if their parents were both 100% quarter horses of 100% foundation breeding!
The double dilutes include cremellos, perlino, and smoky cream which are now accepted quarter horse colors (hooray!).
New dilution genes are now being recognised. The champagne colors occur naturally among quarter horses, with their hazel or greenish eyes and their freckles. Some of these are registered as palomino, or as other cream dilutes, although more and more people recognise the champagne colors as being separate from the cream colors.
The silver dapple (or Taffy) gene does occur very rarely in quarter horses and I predict it will increase in frequency as people become interested in this lovely new (quarter horse) color. Probably there are more American Quarter horses with the silver gene than is currently realised, with some horses being mis-identified, either genuinely or for registration purposes! Also since the gene barely shows itself on red horses there may also be unidentified carriers too.
AQHA set forth strict rules regarding white markings, which should be limited on the face and below the knees. This was despite the fact that foals born of pure-bred parents frequently broke the rule!
Even now the registration certificates of such horses must bear the words: "This horse has white markings designated under AQHA rules as an undesirable trait and uncharacteristic of the breed”. But for one or two alleles in about 60,000 (0.0017-0.0033%) these horses are the same as any other quarter horses and may well have a more ideal conformation and temperament than some solid quarter horses. The money invested to produce them is usually high and their owners are rightly proud them - regardless of their “excessive” white – and they want to show and breed from them.
It seems rather sad that Quarter Horse breeders who get “spotless paint horses”, and paint breeders who get solid foals, have to feel their otherwise quality horses are considered “second class” or unwelcome by some members of both AQHA and the APHA. (And I’m not speaking here as a disgruntled breeder, just as an observer of a peculiar, artificial, and – in my opinion silly – situation!). Another consequence of selecting for minimal white markings is that it occassionally results in foals with the fatal lethal white overo syndrome. The overo spotting pattern is phenotypically heterogeneous and minimally marked horses may show insufficient pattern to be identified as overo horses, even though they have the overo genotype. The AQHA rule will undoubtedly have caused selection for minimally marked overo horses.
Unsurprisingly there are cases of quarter horses having sired or produced lethal white foals, even though they don’t obviously carry the overo gene (i.e. because they have minimal patterning). Not so long ago a somewhat worried lady emailed me alerting me to such a problem. Her stallion – who is without noticeable overo body spotting patterns - had nevertheless been shown to have the overo gene (by molecular testing). Unfortunately he’d already been bred to a couple of mares who also have overo. One only hopes she had a good outcome.
It is clear that quarter horse colors aren't set forever in stone. As more is known so the AQHA rules on quarter horse colors (eventually) change. And when it comes to actual quarter horses, they don't always seem to read the rules. They may well have ideas other than those of the AQHA authorities.
bay horses
Bay horses are commonly seen representing many breeds, although only in one breed, the Cleveland Bay, are the horses exclusively of this color. Ranging in shade from golden brown, to reddish brown to almost a deep purpely brown, bays always have dark points, which are black in standard bays but may be a bit lighter in light bays. Along with dun, bay, especially light bay, was probably one of the colors common among ancestral horses.
the genetics of bay horses
Bay horses must have at least one E+ allele at the extension locus (i.e. bay horses are of genotype E+E+, E+e or E+ea at this locus). This allele causes the production of the black eumelanin pigment that occurs in black, bay and brown horses, and the colors derived from them (e.g. buckskin). The A or agouti locus controls the distribution of black pigment in horses with at least one E+allele: whether it occurs evenly throughout the body, as in true black horses, or only in certain parts, as in brown and bay horses.
The agouti gene controls a switch from normal eumelanin production to a reddish (or sometimes yellowish) form of phaeomelanin in the body of the horse, but not in the mane, tail and points (lower legs and ear rims).
The recessive alleles are Aa and, At. Horses of genotype AaAa have a base color of black, while horses of genotypes AtAt or AtAa have a base color of brown. Brown, including seal brown, is genetically and phenotypically distinct from both black and bay, as explained by Gowers agouti model.
Again according to Gower, bay horses have allele AA, or the wild-type allele A+. It is now the case that (in 2009) 3 alleles have been identified at the molecular level, where previously only 2 were known (the four allele model is certainly a possibility).
f Gower is correct the following explains bay: allele AA is dominant over both At and Aa, but recessive to the wild-type allele A+. A+ is therefore dominant to all other alleles in the series.
Bay horses with allele AA but not A+ are bay, with a black mane, tail and points. Their bodies may be reddish-brown (as in standard, blood and mahogany bays), orange-red (as in copper bays) or yellowish (as in golden bays) and may have a black cast.
Horses with allele A+ are light or wild-type bay. Their points (particularly the lower legs), along with the mane, may be less strongly marked than for other bays (they may be “off-black”). The black on the points may also be more limited than for other bays (e.g. restricted to the fetlocks of the legs). There may be red hairs mixed in with the black portions of the cannon and lower leg, rather than them being solid black.
Light bay is believed to be the original "wild-type" coloring that was commonly found in the horse prior to its domestication. It is still fairly common in wild horses, but is not restricted to them. The muzzle, underside, flanks, and girth area may be lightened in light bay horses. This may be caused by a seperate gene called Pangare (mealy), or it may be another affect of the A+ allele.
A summary of the effects of the A series on black is shown below. Some genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant to AA).
The agouti gene controls a switch from normal eumelanin production to a reddish (or sometimes yellowish) form of phaeomelanin in the body of the horse, but not in the mane, tail and points (lower legs and ear rims).
The recessive alleles are Aa and, At. Horses of genotype AaAa have a base color of black, while horses of genotypes AtAt or AtAa have a base color of brown. Brown, including seal brown, is genetically and phenotypically distinct from both black and bay, as explained by Gowers agouti model.
Again according to Gower, bay horses have allele AA, or the wild-type allele A+. It is now the case that (in 2009) 3 alleles have been identified at the molecular level, where previously only 2 were known (the four allele model is certainly a possibility).
f Gower is correct the following explains bay: allele AA is dominant over both At and Aa, but recessive to the wild-type allele A+. A+ is therefore dominant to all other alleles in the series.
Bay horses with allele AA but not A+ are bay, with a black mane, tail and points. Their bodies may be reddish-brown (as in standard, blood and mahogany bays), orange-red (as in copper bays) or yellowish (as in golden bays) and may have a black cast.
Horses with allele A+ are light or wild-type bay. Their points (particularly the lower legs), along with the mane, may be less strongly marked than for other bays (they may be “off-black”). The black on the points may also be more limited than for other bays (e.g. restricted to the fetlocks of the legs). There may be red hairs mixed in with the black portions of the cannon and lower leg, rather than them being solid black.
Light bay is believed to be the original "wild-type" coloring that was commonly found in the horse prior to its domestication. It is still fairly common in wild horses, but is not restricted to them. The muzzle, underside, flanks, and girth area may be lightened in light bay horses. This may be caused by a seperate gene called Pangare (mealy), or it may be another affect of the A+ allele.
A summary of the effects of the A series on black is shown below. Some genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant to AA).
Genotype at the agouti locus Horses with genotype E+_ at the extension locus
A+_ Light bay
AA_ Bay
At_ Brown
Aa Aa Black
A+_ Light bay
AA_ Bay
At_ Brown
Aa Aa Black
The agouti locus reduces eumelanin production in certain parts of bay and brown horses, probably due to the gene only being operative (“switched-on”) in these parts. Different alleles of the agouti locus are responsible for different forms of phaeomelanin.
breeding bay horses
Suppose we were to breed two bay horses together. We had a bay mare and stallion who were both of genotype E+e at the extension locus (E+ causes the production of the black eumelanin pigment) and of genotype AA Aa at the agouti locus (which controls the distribution of black pigment).
The gametes may now be of four types, any of which are equally likely: E+AA, E+Aa, eAA or eAa. The possible outcomes of the cross can be seen from a Punnett square:
The gametes may now be of four types, any of which are equally likely: E+AA, E+Aa, eAA or eAa. The possible outcomes of the cross can be seen from a Punnett square:
Genetic contribution from stallion:
E+AA E+Aa eAA eAa
E+AA E+Aa eAA eAa
Genetic contribution from mare:
E+AA E+E+AA AA E+E+AAAa E+eAAAA E+eAAAa
Bay Bay Bay Bay
E+Aa E+E+AAAa E+E+AaAa E+eAAAa E+eAaAa
Bay Black Bay Black
eAA E+eAAAA E+eAAAa eeAAAA eeAAAa
Bay Bay Chesnut Chesnut
eAa E+eAAAa E+eAaAa eeAAAa eeAaAa
Bay Black Chesnut Chesnut
E+AA E+E+AA AA E+E+AAAa E+eAAAA E+eAAAa
Bay Bay Bay Bay
E+Aa E+E+AAAa E+E+AaAa E+eAAAa E+eAaAa
Bay Black Bay Black
eAA E+eAAAA E+eAAAa eeAAAA eeAAAa
Bay Bay Chesnut Chesnut
eAa E+eAAAa E+eAaAa eeAAAa eeAaAa
Bay Black Chesnut Chesnut
There is a 9:3:4 of bay: black : chestnut. (The agouti allele in the chestnut horses is irrelevant to the phenotype since there is no black pigment to distribute, either uniformly or in the points.)
If either the mare or the stallion were of genotype E+E+ at the extension locus then only bay, black and brown foals would be possible according to the parents genotypes at the agouti locus.
Breeding bay horses with brown, black or chestnut horses could result in bay foals. Breeding together brown or/and black horses would only give brown or black foals.
One or two copies of the dominant extension allele causes the production of black pigment in bay horses. The browner body, which may be reddish or yellowish brown, is due to at least one copy of a dominant agouti allele. It converts the black pigment to brown, but not in the points, which remain black.
Sooty is a dominant gene there play a big role to in especialy bay an brow, bucksin, baia ect.
If either the mare or the stallion were of genotype E+E+ at the extension locus then only bay, black and brown foals would be possible according to the parents genotypes at the agouti locus.
Breeding bay horses with brown, black or chestnut horses could result in bay foals. Breeding together brown or/and black horses would only give brown or black foals.
One or two copies of the dominant extension allele causes the production of black pigment in bay horses. The browner body, which may be reddish or yellowish brown, is due to at least one copy of a dominant agouti allele. It converts the black pigment to brown, but not in the points, which remain black.
Sooty is a dominant gene there play a big role to in especialy bay an brow, bucksin, baia ect.
black horses
Black horses have long been treasured for their striking beauty, although in many breeds they are relatively infrequent, especially those with jet black coats. They are more common among horses and ponies of cooler climates, for example black is a popular color for Shetland ponies and Shire horses. Black pigment absorbs and retains heat more than other colors, making black coats less suitable in hot climates.
In one breed, the Friesian Horse, consists exclusively of horses with black coats. These horses, of majestic stature and with long flowing manes and tails, are entirely black with no white markings on the legs or face. This ancient breed originated in Friesland (now in Holland) and are said to descend from the ancient horse Equus robustus. A considerable number of Friesian horses were imported into northern England during Roman times and influenced the development of various breeds, most notably the Fell, the Old English Black (which were used in the development of Shire Horses) and the now extinct Galloway and Fen ponies.
In one breed, the Friesian Horse, consists exclusively of horses with black coats. These horses, of majestic stature and with long flowing manes and tails, are entirely black with no white markings on the legs or face. This ancient breed originated in Friesland (now in Holland) and are said to descend from the ancient horse Equus robustus. A considerable number of Friesian horses were imported into northern England during Roman times and influenced the development of various breeds, most notably the Fell, the Old English Black (which were used in the development of Shire Horses) and the now extinct Galloway and Fen ponies.
the genetics of the black coat
Black horses have at least one E+ allele at the extension locus (i.e. they are of genotype E+E+, E+e or E+ea). This dominant allele causes the production of the black eumelanin pigment.
The A or agouti locus controls the distribution of black pigment in horses with at least one E+ allele: whether it occurs evenly throughout the body, as in true black horses, or only in certain parts, as in bays and browns.
The recessive allele Aa of the agouti locus has no effect on eumelanin production. Horses of genotype AaAa therefore have a base color of black. It is the Aa allele that is rare in some breeds. Breeders interested in producing black foals would ideally have horses of genotype AaAa E+E+, i.e. true-breeding blacks.
he coats of some black horses fade – or rather redden - in the sun. The genetic basis of so called fading and non-fading black isn’t currently known. However the phenomenon is well known and not confined to horses, occurring in people and cats, and probably in other animals too.
Since red (chestnut) horses are true-breeding for red it is easy to breed red foals. It is more difficult to breed black ponies and horses, since they may be of genotype E+E+ or they may be heterozygous. Breeding together heterozygous blacks may produce chestnut foals.
The red factor test is useful for people wanting to breed black horses. The red factor test is a molecular genetics test that distinguishes allele E+ from the recessive alleles (e and ea). The test is for (black) horses whose genotype at the extension locus is ambiguous, for example because they have never been used for breeding or because they have only produced one or a few (black) foals.
The A or agouti locus controls the distribution of black pigment in horses with at least one E+ allele: whether it occurs evenly throughout the body, as in true black horses, or only in certain parts, as in bays and browns.
The recessive allele Aa of the agouti locus has no effect on eumelanin production. Horses of genotype AaAa therefore have a base color of black. It is the Aa allele that is rare in some breeds. Breeders interested in producing black foals would ideally have horses of genotype AaAa E+E+, i.e. true-breeding blacks.
he coats of some black horses fade – or rather redden - in the sun. The genetic basis of so called fading and non-fading black isn’t currently known. However the phenomenon is well known and not confined to horses, occurring in people and cats, and probably in other animals too.
Since red (chestnut) horses are true-breeding for red it is easy to breed red foals. It is more difficult to breed black ponies and horses, since they may be of genotype E+E+ or they may be heterozygous. Breeding together heterozygous blacks may produce chestnut foals.
The red factor test is useful for people wanting to breed black horses. The red factor test is a molecular genetics test that distinguishes allele E+ from the recessive alleles (e and ea). The test is for (black) horses whose genotype at the extension locus is ambiguous, for example because they have never been used for breeding or because they have only produced one or a few (black) foals.
Red Factor Test
The red factor test is a DNA test now available for black horses whose to genotype at the extension locus is ambiguous. This is useful information for people wanting to breed black horses. It says if a black horse can pass on the allele of the extension gene responsible for chestnut. Horses heterozygous at this gene could have chestnut foals or foals of a chestnut related colour, such as palomino, if they're bred to another horse with the chestnut allele.
Tuxedo, a 17 hands 2" Thoroughbred, has been tested homozygous for the dominant allele of the extension locus. This makes him a "true-breeding black". This means he won't pass on chestnut to his foals. Whether any particular foal is black (or bay, for example) depends on the mare as well as the stallion. They will not however ever be chestnut, even if the dam is chestnut.
Tuxedo had a successful racing career in Pennsylvania, with earnings of over $44,000. He now stands at Red Fox Farm, Texas. Thanks to Milynda Milam for allowing me to display this photo.
Tuxedo had a successful racing career in Pennsylvania, with earnings of over $44,000. He now stands at Red Fox Farm, Texas. Thanks to Milynda Milam for allowing me to display this photo.
Researchers at the Swedish University of Agricultural Sciences found that the alleles producing black and red pigment differed by a single nucleotide that resulted in a single amino acid change in the protein encoded by the gene. (Nucleotides are one of the building blocks of genes, amino acids are the building blocks of the proteins). The test discriminates between the dominant and recessive alleles of the extension gene by detecting which nucleotide is present at the distinguishing site in the gene.
The red factor test is only informative about one part of the genotype, although many more genes are responsible for creating horse coat colors. The agouti gene, for example, controls the distribution of black pigment, and no molecular test is presently available to help breeders screen horses for genetic variation at the agouti locus. However since black horses are homozygous for the most recessive allele of the agouti locus breeders can be sure that black horses will be true breeding for this gene, and don’t need to worry about it.
The red factor test is only informative about one part of the genotype, although many more genes are responsible for creating horse coat colors. The agouti gene, for example, controls the distribution of black pigment, and no molecular test is presently available to help breeders screen horses for genetic variation at the agouti locus. However since black horses are homozygous for the most recessive allele of the agouti locus breeders can be sure that black horses will be true breeding for this gene, and don’t need to worry about it.
brown horses
Brown horses can be various shades from light brown to almost completely black. Their bodies may be shaded black and brown or be mostly black (which is often called seal brown). Their soft parts, such as the muzzle and eyebrows, and around the flanks, quarters and girth, are red or golden brown (sometimes called “mealy”). Seal browns are often mistaken for black horses, but the coloring on the soft parts identifies them as brown. They are also genetically distinct from black horses, as discussed below.
Some aspects of colour are uncertain, this includes the genetics of brown horses. They’re not exactly black, they’re not bay.
Seal browns were,until recently, commonly thought to be black horses with a gene called “mealy”, giving pale red or yellowish areas on the lower belly, flanks, behind the elbows, inside the legs, muzzle and over the eyes. Pangarré was thought to be caused by a dominant gene symbolized as Pa+ (it‘s other name is pangarré). Some thought that the same gene caused sorrel chestnut (the lightest shade of chestnut, Thiruvenkadan et al, 2008). However, McCann (1916) reported that sorrel is recessive to chestnut and mating among sorrel horses gives sorrel offspring only. That is certainly inconsistent with sorrel being caused by a dominant gene. It is now known that, consistent with the theory of Gower, seal brown is due to the At allele at the agouti locus. This allele has been sequenced and there is now a test for it.
Some horses are more or less uniformly brown. Some of these are due to the action of dilution alleles, such as champagne, on an otherwise black coat. I’ve seen a beautiful chocolaty brown coloured warm blood that tested black, with non of the dilution genes for which there’s currently a test. This could be black with an unknown dilution gene, or it could be that it has a variant agouti allele.
Some aspects of colour are uncertain, this includes the genetics of brown horses. They’re not exactly black, they’re not bay.
Seal browns were,until recently, commonly thought to be black horses with a gene called “mealy”, giving pale red or yellowish areas on the lower belly, flanks, behind the elbows, inside the legs, muzzle and over the eyes. Pangarré was thought to be caused by a dominant gene symbolized as Pa+ (it‘s other name is pangarré). Some thought that the same gene caused sorrel chestnut (the lightest shade of chestnut, Thiruvenkadan et al, 2008). However, McCann (1916) reported that sorrel is recessive to chestnut and mating among sorrel horses gives sorrel offspring only. That is certainly inconsistent with sorrel being caused by a dominant gene. It is now known that, consistent with the theory of Gower, seal brown is due to the At allele at the agouti locus. This allele has been sequenced and there is now a test for it.
Some horses are more or less uniformly brown. Some of these are due to the action of dilution alleles, such as champagne, on an otherwise black coat. I’ve seen a beautiful chocolaty brown coloured warm blood that tested black, with non of the dilution genes for which there’s currently a test. This could be black with an unknown dilution gene, or it could be that it has a variant agouti allele.
the genetics of brown horses according to the Gower model
It is now known that seal brown is due to the At allele at the agouti locus. This allele has been sequenced and there is now a test for it. This is further evidence that the following theory is correct, certainly it shows that Gower, and others, were correct in anticipating a brown agouti allele.
Brown horses must have at least one E+ allele at the extension locus (i.e. they are of genotype E+E+, E+e or E+ea at this locus). This allele causes the production of the black eumelanin pigment that occurs in black, brown and bay horses, and the colors derived from them (e.g. buckskin).
The A or agouti locus controls the distribution of black pigment in horses with at least one E+ allele: whether it occurs evenly throughout the body, as in true black horses, or only in certain parts, as in brown and bay horses. Brown horses are of genotypes AtAtor AtAa at this locus.
The recessive allele Aa has no effect on eumelanin (black pigment) production. Horses of genotype AaAa therefore have a base color of black. The allele At is dominant over Aa, but recessive to the other alleles of the agouti series. Molecular genetic tests have confirmed that seal browns are not blacks and do not have the AaAa genotype. This is contrary to a previous theory that seal brown horses were in fact black horses with the Pangarre (or mealy) trait (which is thought to be caused by a seperate gene, though one wonders about this).
The At allele obviously causes less restriction of black pigment than the bay alleles of the agouti locus. However we know that brown is genetically distinct from bay since breeding brown horses together only ever results in brown or black foals, and not bay ones.
A summary of the effects of the A series on black is shown below. Some genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant to AA).
Brown horses must have at least one E+ allele at the extension locus (i.e. they are of genotype E+E+, E+e or E+ea at this locus). This allele causes the production of the black eumelanin pigment that occurs in black, brown and bay horses, and the colors derived from them (e.g. buckskin).
The A or agouti locus controls the distribution of black pigment in horses with at least one E+ allele: whether it occurs evenly throughout the body, as in true black horses, or only in certain parts, as in brown and bay horses. Brown horses are of genotypes AtAtor AtAa at this locus.
The recessive allele Aa has no effect on eumelanin (black pigment) production. Horses of genotype AaAa therefore have a base color of black. The allele At is dominant over Aa, but recessive to the other alleles of the agouti series. Molecular genetic tests have confirmed that seal browns are not blacks and do not have the AaAa genotype. This is contrary to a previous theory that seal brown horses were in fact black horses with the Pangarre (or mealy) trait (which is thought to be caused by a seperate gene, though one wonders about this).
The At allele obviously causes less restriction of black pigment than the bay alleles of the agouti locus. However we know that brown is genetically distinct from bay since breeding brown horses together only ever results in brown or black foals, and not bay ones.
A summary of the effects of the A series on black is shown below. Some genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant to AA).
Genotype at the agouti locus Horses with genotype E+_ at the extension locus
A+_ Light bay
AA_ Bay
At_ Brown
Aa Aa Black
AA_ Bay
At_ Brown
Aa Aa Black
The agouti locus reduces eumelanin (black pigment) production in brown horses, probably due to the gene only being operative (“switched-on”) in certain parts. Different alleles of the agouti locus are responsible for different forms of phaeomelanin (red/ brown pigment).
breeding brown horses
In cases where a "brown" colour is due to a dilution of black then crossing brown horses together would result in black, brown and chestnut foals, and other dilute types depending on whether the dilution gene(s) is/are dominant or recessive, and whether red pigment is affected as well as black (perhaps to make chestnut into sorrel).
Where brown horse have the brown agouti allele then breeding brown horses together would also result in brown, black or chestnut foals, but not bay ones, as follows below. If Gower is also right about the affect of the alleles on shades, the chestnut foals would be expected to be liver and standard chestnut, rather than the chestnut and sorrel which might be more likely for a dilution model.
If both the parents are heterozygous at the extension locus then there is a 1 in 4 (25%) chance of the foal being chestnut. If one or both of the parents are of genotype E+E+ then only black or brown foals can result. Black foals will only be produced if both parents are of genotype AtAa at the agouti locus.
The following demonstrates what happens when two brown horses are bred together which are both heterozygous at both loci:
Where brown horse have the brown agouti allele then breeding brown horses together would also result in brown, black or chestnut foals, but not bay ones, as follows below. If Gower is also right about the affect of the alleles on shades, the chestnut foals would be expected to be liver and standard chestnut, rather than the chestnut and sorrel which might be more likely for a dilution model.
If both the parents are heterozygous at the extension locus then there is a 1 in 4 (25%) chance of the foal being chestnut. If one or both of the parents are of genotype E+E+ then only black or brown foals can result. Black foals will only be produced if both parents are of genotype AtAa at the agouti locus.
The following demonstrates what happens when two brown horses are bred together which are both heterozygous at both loci:
Genetic contribution from stallion:
E+At E+Aa eAt eAa
Genetic contribution from mare:
E+At E+E+AtAt E+E+AtAa E+eAtAt E+eAtAa brown brown brown brown
E+Aa E+E+AtAa E+E+AaAa E+eAtAa E+eAaAa
brown black brown black
eAt E+eAtAt E+eAtAa eeAtAt eeAtAa
brown brown chestnut chestnut
eAa E+eAtAa E+eAaAa eeAtAa eeAaAa
brown black chestnut chestnut
There is a 9:3:4 ratio of brown: black : chestnut, or put another there is just over 56% chance of a brown foal from any particular breeding. (The agouti allele in the chestnut horses is irrelevant to the phenotype since there is no black pigment to distribute, either uniformly or in the points.)
buckskin horses
Buckskin horses are horses with a base coat color of bay or brown (i.e. of genotype Ee or EE at the extension locus) and genotype C+CCr at the C locus (the cream dilution gene). Their bodies vary in shade from pale cream to a deep rich golden color. Their manes and tails are dark, either black or very dark brown. The coat may change shade with the seasons.
Smoky black horses are sometimes called black buckskins or (especially in the UK) dilute blacks. These are black horses with a cream gene. They may be very difficult to identify and may look brown, bay, liver chestnut or faded black. The CCr allele is semi-dominant and dilutes red pigment to yellow in a single dose but has only a very subtle effect on black pigment. The wild-type C+ allele is effectively recessive since it needs to be homozygous for there to be no dilution of the base color.
Gowers model of agouti affects on buckskin
According to the Gower model the agouti locus affects the shade of buckskin. Different alleles of the agouti locus seem to be responsible for different shades of cream and yellow, as well as affecting the distribution of dark pigment.
A summary of the assumed effects of the A series on base color and buckskin is shown in the table below. Genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant over all other alleles). Allele Aa is recessive to all the other alleles at the agouti locus. The At (brown), previously only hypothesised, has now been shown to exist, and there is a molecular test for it.
A summary of the assumed effects of the A series on base color and buckskin is shown in the table below. Genotypes are shown using an underscore, e.g. AA_. This represents where an allele can either be the same as the allele shown (i.e. AA in the example) or any other allele recessive to it (i.e. either At or Aa in the example, but not A+ which is dominant over all other alleles). Allele Aa is recessive to all the other alleles at the agouti locus. The At (brown), previously only hypothesised, has now been shown to exist, and there is a molecular test for it.
Genotype at the agouti locus Bay horsesbuckskin horses
A+_ Light bay Cream buckskin
AA AA Bay, possibly having a redder coat than AA_ probably golden buckskin
AA_ Bay probably standard buckskin
At_ brown brown, mouse or sooty buckskin
Aa Aa black smoky black
AA AA Bay, possibly having a redder coat than AA_ probably golden buckskin
AA_ Bay probably standard buckskin
At_ brown brown, mouse or sooty buckskin
Aa Aa black smoky black
breeding buckskin horses
Since buckskin horses are heterozygous for the cream dilution gene they do not breed true, being able to produce foals of any base or cream dilute color when bred together.
The scheme below shows what happens when two buckskin horses are bred together.
There’s a 25% chance of a base colored foal. This could be black, brown, bay or chestnut, depending on the genotype at the agouti and extension loci. There’s also a 25% chance of a double dilute foal, which could be cremello, perlino or smoky cream, again depending on the genotype at the agouti and extension loci. There’s a 25% chance of a foal inheriting the dilution gene from the mare only and a 25% chance of a foal inheriting the dilution gene from only the stallion, giving a 50% chance overall of a single dilute foal, which could be palomino, buckskin or smoky black.
Buckskin foals, like bay foals, are often born without fully pointed lower legs (which may therefore be pale, as in some of the photos above). The black points begin to show when the foal coat is shed.
The scheme below shows what happens when two buckskin horses are bred together.
There’s a 25% chance of a base colored foal. This could be black, brown, bay or chestnut, depending on the genotype at the agouti and extension loci. There’s also a 25% chance of a double dilute foal, which could be cremello, perlino or smoky cream, again depending on the genotype at the agouti and extension loci. There’s a 25% chance of a foal inheriting the dilution gene from the mare only and a 25% chance of a foal inheriting the dilution gene from only the stallion, giving a 50% chance overall of a single dilute foal, which could be palomino, buckskin or smoky black.
Buckskin foals, like bay foals, are often born without fully pointed lower legs (which may therefore be pale, as in some of the photos above). The black points begin to show when the foal coat is shed.
Genetic contribution from stallion:
50% chance of either allele in the sperm
C+ CCr
Genetic contribution from mare:
50% chance of either allele in the egg
C+ 25% chance: C+C+ 25%chance: base color C+ CCr single dilute
CCr 25% chance: C+ CCr 25% chance: CCr CCr single dilute double dilute
The only guaranteed way of producing buckskin horses is to use one perlino parent and one bay or brown parent. At least one parent must be homozygous for the wild-type allele at the extension locus, which could be tested for using the red factor test. Also at least one parent must not carry the black allele Aa at the agouti locus, for which a new molecular test now exists. Alternatively use a stallion that has never sired a chestnut, palomino, cremello, black, smoky black or smoky cream foal. This increases your odds of a buckskin foal but doesn’t guarantee it.
Point coloration
In horses, point coloration is produced by the action of the Agouti gene, which acts on the extension gene, when present, to suppress black color to all but the extremities of the horse; the legs, mane, tail and tips of the ears. This is redered to as Baia colored, thise horse is on a Black brown base color.
If the extension gene is not present, the effect of agouti is not visible, as there is no black color present to suppress. this is refered to as a Baio colored.
Points are most typically seen on a bay-colored horse, which has a black mane, tail, legs and ear tips while the body and head will show the underlying chestnut or "red" base color from the brown side of the genes, where the baio dont have the points from the brown genes on ther legs, the red is dominantin over the brown base color. The real Baio horse color i rear.
Point coloration may also be visible on horses with dilution genes that act upon a bay base coat such as the dun gene and a single copy of the cream gene. Other genes or white markings may affect a horse's coat color in addition to agouti, and if present, can further alter or suppress black hair color and may mask any point coloration.
Any horse breed may have point coloration with the exception of a very small number of horse breeds where humans have specifically used selective breeding to eliminate the agouti gene.
Brindle
Brindle is a coat coloring pattern in animals, particularly dogs, cattle, guinea pigs, and, rarely, horses. It is sometimes described as "tiger-striped", although the brindle pattern is more subtle than that of a tiger's coat.
The streaks of color are irregular and usually darker than the base color of the coat, although very dark markings can be seen on a coat that is only slightly lighter.
Brindle coloring in horses is extremely rare and in many cases is linked to spontaneous chimerism, resulting in an animal with two sets of DNA, with the brindle pattern being an expression of two different sets of equine coat color genes in one horse.
This form is not heritable.
In some horses the pattern seems to be inherited, indicating that one or more genes are responsible. One heritable brindle pattern in a family of American Quarter Horses was identified in 2016 and named Brindle1 (BR1).The Brindle1 phenotype has an X-linked, semidominantmode of inheritance. Female horses with this gene have a striped coat pattern, plus hairs from the stripes have a different texture as well as color, less straight and unrulier.
Male horses have sparse manes and tails but do not show a striped coat texture pattern. A Brindle1 test is available.
Brindle coloring consists of irregular stripes extending vertically over the horse's body and horizontally around the legs. Brindle horses can also have a dorsal stripe. It usually does not affect the head and legs as much as the body, with the heaviest concentrations of brindling being on the neck, shoulders and hindquarters. The coloring has been documented in the past. At the Zoological Museum of the Academy of Science in Leningrad, a Russian cab horse of brindle coloring from the early 19th century was mounted and put on display due to its rarity.
Descriptio. The brindling pattern found in horses could be described as vertical stripes that are found along the neck, back, hindquarters, and upper legs. The horse's head is usually a solid color and is not affected by the striping. The brindling pattern has no effect on dark points on horses. Some brindle-colored horses are more eye-catching than others.
With this rare coat pattern there is a base coat that covers the entire body of the horse. This base coat color can be any color. Recorded examples have been bay, chestnut, palomino, and dun. Earliest documented cases were said to have red dun or grulla as a base coat. Over top of the base color is either a lighter or darker color, giving the appearance of stripes.
The streaks of color are irregular and usually darker than the base color of the coat, although very dark markings can be seen on a coat that is only slightly lighter.
Brindle coloring in horses is extremely rare and in many cases is linked to spontaneous chimerism, resulting in an animal with two sets of DNA, with the brindle pattern being an expression of two different sets of equine coat color genes in one horse.
This form is not heritable.
In some horses the pattern seems to be inherited, indicating that one or more genes are responsible. One heritable brindle pattern in a family of American Quarter Horses was identified in 2016 and named Brindle1 (BR1).The Brindle1 phenotype has an X-linked, semidominantmode of inheritance. Female horses with this gene have a striped coat pattern, plus hairs from the stripes have a different texture as well as color, less straight and unrulier.
Male horses have sparse manes and tails but do not show a striped coat texture pattern. A Brindle1 test is available.
Brindle coloring consists of irregular stripes extending vertically over the horse's body and horizontally around the legs. Brindle horses can also have a dorsal stripe. It usually does not affect the head and legs as much as the body, with the heaviest concentrations of brindling being on the neck, shoulders and hindquarters. The coloring has been documented in the past. At the Zoological Museum of the Academy of Science in Leningrad, a Russian cab horse of brindle coloring from the early 19th century was mounted and put on display due to its rarity.
Descriptio. The brindling pattern found in horses could be described as vertical stripes that are found along the neck, back, hindquarters, and upper legs. The horse's head is usually a solid color and is not affected by the striping. The brindling pattern has no effect on dark points on horses. Some brindle-colored horses are more eye-catching than others.
With this rare coat pattern there is a base coat that covers the entire body of the horse. This base coat color can be any color. Recorded examples have been bay, chestnut, palomino, and dun. Earliest documented cases were said to have red dun or grulla as a base coat. Over top of the base color is either a lighter or darker color, giving the appearance of stripes.
Brindle Coat Texture
The molecular basis of a striped coat texture pattern that produces a brindle phenotype in a lineage of Quarter Horses has been identified by researchers in Switzerland. To avoid confusion with the spontaneous, not heritable brindle pattern associated with chimerism, the coat texture pattern has been named Brindle 1 (BR1). The stripes form a vertical pattern from the back to the sides of horses that is characterized by changes in hair structure as well as pigmentation. The hairs from the stripes are less straight and unrulier than hairs from the normally pigmented and textured coat. The BR1 phenotype is variable in that in some females, the predominant feature is the coat texture change while in others it can be the striped pigmentation. Males with BR1 mutation have sparse manes and tails but not the texture pattern. The BR1 phenotype can occur in any color background and shows seasonal changes (summer versus winter), with winter coat often having a “moth-eaten” appearance. The BR1 phenotype has an X-linked, semi-dominant mode of inheritance. Females with 1 or 2 copies of the BR1 mutation exhibit the brindle phenotype whereas BR1 males (only 1 X-chromosome present) have sparse manes and tails but not the striped coat texture pattern.
The Veterinary Genetics Laboratory offers a test for Brindle.
The Veterinary Genetics Laboratory offers a test for Brindle.
Results are reported as:
N/NNo copies of the BR1 mutation detected in female horse.
NNo copies of the BR1 mutation detected in male horse.
N/BR1One copy of the BR1 mutation detected in female horse. Striping pattern is expected.
BR1/BR1 Two copies of the BR1 mutation detected in female horse. Striping pattern is expected.
BR1 One copy of the BR1 mutation detected in male horse. Horse may display sparse mane and tail.
N/NNo copies of the BR1 mutation detected in female horse.
NNo copies of the BR1 mutation detected in male horse.
N/BR1One copy of the BR1 mutation detected in female horse. Striping pattern is expected.
BR1/BR1 Two copies of the BR1 mutation detected in female horse. Striping pattern is expected.
BR1 One copy of the BR1 mutation detected in male horse. Horse may display sparse mane and tail.
Horse Color Testing Labs
by Daylene Alford November 17, 2011 Updated November 26, 2015Color Testing LabsThe following labs provide DNA color testing. This list is not meant to be comprehensive nor meant as an endorsement of any of the labs listed. If you know of a lab that is not listed please contact me so it can be added. UC Davis(link is external)
Equine
by Daylene Alford November 17, 2011 Updated November 26, 2015Color Testing LabsThe following labs provide DNA color testing. This list is not meant to be comprehensive nor meant as an endorsement of any of the labs listed. If you know of a lab that is not listed please contact me so it can be added. UC Davis(link is external)
- Red Factor
- Agouti
- Champagne
- Cream
- Pearl
- Silver
- Lethal White Overo
- Sabino1
- Tobiano
- Dun (Marker test not actual mutation)
- Roan Zygosity
- Dominant White W10 mutation
- Camarillo White - W4
- Gray
- Splashed White (3 mutations)
- Leopard Complex & Congenital Stationary Night Blindness
- Appaloosa Pattern-1 (PATN1)
Animal Genetics Incorporated(link is external)- Gray
- Champagne
- Tobiano
- Red/Black Factor
- Lethal White Overo
- Agouti
- Sabino 1
- Cream
- Silver
- Pearl
- Dominant White (W3,W5,W10)
- Splashed White
- Appaloosa (LP)
- Dun (The actual mutation!)
- Agouti
- Red/Black Factor
- Cream
- Champagne
- Sabino 1
- Silver
- Tobiano
- Gray
- Red Factor
- Agouti
- Cream
- Champagne
- Pearl
- Silver
- Tobiano
- Frame (LWO)
- Sabino 1
- Gray
- Dominant White 10 and 5
- Agouti
- Extension
- Cream
- Champagne
- Silver
- Grey
- Frame overo (OLWS)
- Appaloosa or leopard complex
- Tobiano
- Sabino 1
- SW1 (Splashed White 1)
- W20 white markings
- Offers a genetics panel that includes colors and genetic diseases and performace traits http://www.etalondx.com/#!services/ch6q(link is external)
Equine