Performance Horses LLC Heartridge
Home Foals Prospects Stallions Mares For Sale Information About Us Contact Us Gallery
General There are two base colors from which all other colors are made; Red, represented as “e” and Black, represented as “E”. ‘Red Based’ horses are Chestnuts/Sorrels, Red Duns, Red Roans, Palominos, Cremellos, etc. ‘Black Based’ horses are Black, Bay, Brown, Grullo, Bay Dun, Buckskin, Perlino, Smoky Cream, etc. Black is dominant over Red, thus making Red a recessive gene. For example, a horse that is carrying one Black gene (E) and one Red gene (e) will always be black or black based in color; however this horse has the potential to produce a red foal.
Heterozygous & Homozygous There are two terms in equine genetics you will need to know to understand how color modifiers, dilutions and white patterns affect the horse’s appearance, and the color probability of the foals it may produce. These two terms are Heterozygous and Homozygous. Heterozygous: The horse carries ONE copy of a gene and will have a 50% chance of passing it to its offspring. Homozygous: The horse carries TWO copies of a gene and will have a 100% chance of passing it to its offspring. In other words, it can only pass that particular gene to its foals. Horses need to receive one of the same genes from BOTH dam and sire to be homozygous; meaning both the dam and the sire must have the same gene to pass on. Going back to Red & Black, we will go through some examples of Heterozygous and Homozygous genes. If a horse is carrying one Red gene and one Black gene (Ee) it is Heterozygous and will be black in color. This means that the horse has a 50% chance of passing on a Red or a Black gene to its offspring.   If a horse is carrying two Black genes (EE) it is Homozygous black. The horse will be black in color and can only pass on one black gene to its foals because it does not have a red gene. In other words, all offspring from this horse will be Black or Black based in color. If a horse is carrying two Red genes (ee) the horse will be red in color and can only pass on one red gene to its foals because it does not have a black gene. This does not mean that all its foals will be red based because Black is dominant over Red. This means that when breeding a red horse (ee) to a black horse (Ee or EE), if the foal receives one red gene from one parent and a black gene from the other the foal will be black in color.

Equine Colour Genetics...

Colour Modifiers & Dilutions Agouti  Black to Bay or Brown. Red is Unaffected. Grey  All colors lose pigment over time. Cream  Bay to Buckskin, Chestnut to Palomino, etc Dun  Black to Grullo, Bay to Bay Dun, Buckskin to Dunskin, etc. Champagne  Black to Classic, Bay to Amber, Chestnut to Gold, Brown to Sable, etc. Silver  Black to classic Silver Dapple, Bay to Silver Dapple Bay, etc. Red is unaffected. Pearl  Homozygous form mimics Champagne. Heterozygous form, no change in appearance unless combined with a cream gene. Satin Gene - Possibly? AGOUTI - One of the most common coat color modifiers is the Agouti gene represented as “A”. Agouti is a gene that only affects black pigment and restricts the black hair to “Points” on a horse such as the legs, mane, tail, tips of the ears, etc. This produces the colors we know as Bay, Brown, Buckskin, Bay Dun, etc. Chestnuts can carry Agouti but it will not manifest itself on their coat as they are a red based horse, and the Agouti only affects black hair. There are three strains of Agouti: 1. Wild type, represented as “A+” 2. Regular type, represented as “A” 3. Seal Brown type, represented as “At” Wild type Agouti restricts the black hair the most, often pushing the black well below the hocks and knees of a horse giving them the appearance of black socks. Wild bays do still have a fully black mane and tail. The rest of the horse’s body where the black hair has been restricted will be “red”. Wild type Agouti is dominant over Regular & Seal Brown agouti. Regular Agouti is what most people are familiar with and is what produces the common Bay Horse. The black hair is restricted to the legs, mane and tail, tips of the ears, eyes and muzzle. The rest of the horse’s body will be “red.” Regular Agouti is dominant over Seal Brown Agouti, but not Wild Type. Seal Brown Agouti restricts the least amount of black hair, although the extent of how much of the black pigment is restricted varies. Some seal brown horses are nearly all black except for “red” or tan around their muzzle, in their flanks, and sometimes around the eye and elbow area. We call these the “soft spots” of a horse.  This can sometimes give a “mealy” appearance. Some seal brown horses however, can look like a dark bay, and it can be hard to distinguish between the two.   A horse can carry one or two of the three Agouti types. For example, a horse may have only a Wild type Agouti (A+a), or it can have both a regular and a wild type (A+A). Because Wild type agouti is dominant over Regular type agouti, if a horse has both genes its appearance will be Wild Bay, but it has the potential to produce Regular Bay foals. The same goes for if a horse is carrying one Regular agouti gene and one seal brown agouti gene (AAt). The horse will appear bay, but it may produce a seal brown foal.   When a horse is carrying two Agouti genes, whatever they may be, the horse is Homozygous Agouti. Homozygous agouti can look like any of these: AA: Homozygous regular agouti; Horse will appear Bay. All foals will carry “A” agouti. All Black based colored horses will have black restricted to “points”. A+A+: Homozygous wild agouti; Horse will appear Wild Bay. All foals will carry “A⁺” agouti. All Black based colored horses will have black restricted to mane & tail and lower legs, resembling black socks. A+A: Homozygous Agouti; Horse will appear Wild Bay. All foals will receive an agouti gene. 50% of foals will carry wild type agouti, 50% of foals will carry Regular type agouti. A+At: Homozygous Agouti; Horse will appear Wild Bay. All foals will receive an agouti gene. 50% of foals will carry a wild type agouti, 50% of foals will carry Seal Brown type agouti. AtAt: Homozygous Seal Brown Agouti; Horse will appear Brown. All foals will carry “At” agouti. All Black based colored horses will have black restricted from the “soft spots” of the horse. AAt: Homozygous Agouti; Horse will appear Bay. All foals will receive an agouti gene. 50% of foals will carry regular type agouti, 50% of foals will carry Seal Brown agouti. Heterozygous Agouti can look like any of these: Aa: Heterozygous regular agouti; Horse will appear Bay. 50% of foals will carry “A” agouti. A+a: Heterozygous Wild type agouti; Horse will appear Wild Bay. 50% of foals will carry “A⁺” agouti. Ata: Heterozygous Seal Brown agouti; Horse will appear Brown. 50% of foals willy carry “At” agouti. All forms of Agouti are dominant over Black. This means that when a black horse is carrying agouti, it will always be a form of Bay or Brown. A black horse cannot carry agouti and still be completely black. This is why when sometimes breeding a Black horse to a Chestnut they produce a bay. This is because the Chestnut is carrying an Agouti gene that it has passed on to its offspring resulting in a bay foal, but the chestnut doesn’t exhibit it because Agouti only affects Black hair, not Red.
GREY MODIFIER - Grey is one of the other most common coat color modifiers in horses. Oft times we see a “white” horse, when in reality the horse has actually lost all pigment in its coat over time which has left it appearing white. The skin will still be black, and the eyes brown, unless there is another color modifier or dilution in play as well. While there are “White” horses, this is actually due to a white pattern rather than a coat color modifier and they are unrelated to Grey. True White horses will be explained further on. The Grey modifier eventually takes out all colour pigment in the horse’s hair. When a horse has lost all pigment in its coat and appears to be white or light grey, it is called “greyed out”. The speed at which a horse greys out varies. Some horses Grey out in just a couple of months to years, while others can take many years to grey out. Grey is a dominant gene that affects all colors, so if a horse is carrying at least one Grey gene it will eventually grey out.   In order for a horse to turn Grey, it must have a Grey gene, and in order for it to have a grey gene, one parent must have carried at least one grey gene to pass it on to its offspring. A horse that is starting to grey out will usually start around the head area. Around the eye is usually the first hair to turn grey and it spreads from there. The grey will seem to travel from the horse’s head down its neck to the rest of its body, where it will begin to grey more uniformly. There are several different shades of grey horses; Dappled Grey, Fleabitten Grey, Rose Grey, White Grey, etc, but they all come from the one gene. The Grey gene is represented by “G”. GG: Homozygous Grey; Horse will appear Grey or eventually Grey out. All foals will receive a “G” gene and eventually grey out. Gg: Heterozygous Grey; Horse will appear Grey or eventually Grey out. 50% of foals will receive a “G” gene and grey out.
CREAM DILUTION - Cream is a dilution gene found in breeds such as Quarter Horse, Paint, Saddlebred, Morgan, Akhal-Teke, Mustang, and sometimes even Thoroughbreds. The Cream Gene is represented by “Cr” or “CR” and is what is called an incomplete dominant gene. This means that it will express itself differently in heterozygous form (nCr) and homozygous form (CrCr). For Example; a bay horse with one cream gene becomes buckskin and is heterozygous Cream. The red hair is lightened to a pale to rich golden color and sometimes the black hair will look sun bleached. It will have a 50% chance of producing cream diluted foals. A bay horse with two cream genes becomes a Perlino and is homozygous Cream. In homozygous form cream dilutes the coat color to an almost ivory or cream color, the skin becomes pink and the eyes become a pale blue or bluish- green. It should also be noted that cream does not always have an effect on black hair in heterozygous form. In other words, a black horse with one cream gene (called a Smoky Black) may still look plain black, while a different Smoky Black horse may look like a very sunbleached black horse or a dark bay or brown.   nCr: Heterozygous Cream horses are sometimes called “Single Dilutes”. These horses will have a 50% chance of producing Single Dilute foals like themselves, and 50% chance on producing non-dilute foals. Single Dilutes consist of: Smoky Black (Black + 1 Cream gene) Buckskin (Bay + 1 Cream gene) Palomino (Chestnut + 1 Cream gene), etc CrCr: Homozygous Cream horses are sometimes called “Double Dilutes”. These horses will always pass on one cream gene to their offspring, resulting in single dilute foals. Double Dilutes consist of: Smoky Cream (Black + 2 Cream genes) Perlino (Bay + 2 Cream genes) Cremello (Chestnut +2 Cream genes), etc
Breeding a red based horse (ee) to another red based horse (ee) will always produce a red based foal (ee).
Breeding a heterozygous black horse (Ee) to a red horse (ee) will result in a 50% chance of a black foal and 50% chance of a red foal.
Breeding a Homozygous black horse (EE) to a red horse (ee) will always produce a Heterozygous Black foal (Ee).
Breeding a Heterozygous black horse (Ee) to another Heterozygous black horse (Ee) will result in a 75% chance of a black foal, either heterozygous (Ee – 50% chance) or homozygous (EE – 25% chance) and a 25% chance of a red foal (ee).
Breeding a Homozygous black horse (EE) to another Homozygous black horse (EE) will always produce a homozygous black foal (EE).
Copyright © Heartridge Performance Horses LLC.2014. All rights reserved. Website created by About Solutions: www.aboutsolutions.ca
Next e       e e e ee     ee red    red ee     ee red    red E       E E E EE     EE black   black    EE    EE black   black E       e E e EE      eE  black  black    Ee      ee black   red E       e e e Ee     ee black   red Ee     ee black   red E      E e e Ee     Ee black   black    Ee     Ee black   black