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What will be the color of my foal?

 

First here are some terms you will need to know when discussing genetics:

Genes: the DNA/genetic information for a horse is coded on strands of protein found in the nuclei of cells. A 'gene' is an actual DNA sequence or ëspotí on these strands that can be identified with a specific characteristic, such as coat color.

Homozygous/Heterozygous: these two terms relate to the gene pairs at a specific location ('spot' or loci). If the genes are homozygous, then they are the same. Heterozygous means they are different. (Example, palominos are always heterozygous for the cremello gene, cremellos are always homozygous.)

Genotype: What the genes of the horse are.

Phenotype: What the horse actually looks like.

Read the definitions for genotype and phenotype again. They are a very important part of understanding why a horse can look one way, and throw something completely unexpected.

All horses come with two basic coat colors, Red (CC) and Black (EE or Ee). Base Red coat color phenotypes are Sorrel, Chestnut, Palomino, Cremello, Red Roan and Red Dun. Base Black coat color phenotypes are Bay, Brown, Black, Buckskin, Perlino, Dun, Grullo, Roan and Blue Roan. (Grey will be discussed later.) It is also very important to understand that Red is recessive, (or masked) by the Black gene. This is why two black parents will produce Sorrel/Chestnut foals. You should never get a horse in the black family if you breed two horses in the red family together, no mater what those grand parents looked like. However the reverse is not true. Two black family parents can produce both Red family and Black family foals.

Genotypically, Sorrel and Chestnuts look like this: ( aa, ee, CC, dd, rr, gg ). Many registries try to separate these two colors, but for this article we are talking about the typical red to red-brown horse with no black points and manes that vary from almost black to off white (but not palomino). Some Chestnuts could almost be black but the difference is obvious when you look for black
points on the legs. Sorrel to Sorrel will always produce chestnut/sorrel foal, and I might add will never produce anything else. Genotypiclly these horses are recessive for everything, and when you mate recessives to recessives you will always know the outcome because it will be recessive genetically and phenotypically. (Genetically the Sorrel/Chestnut gene is shown as CC in caps, I
don't know why because it is a recessive-- one of those darn exceptions.)

Black horse geneticly are: ( aa, E -, cc, dd, rr, gg ). The ' - ' means it can be 'EE' or 'Ee' in this genetic spot. Black is a color that has varying definitions but here it will mean a horse that sheds black two times a year, with no brown or red hairs any where, even though they fade over the winter or summer months. (Black is also one of those colors affected by subtle genes that will not be addressed here except for brown.)

Black has one interesting trick. When a cremello gene is added to a black horse, it is very hard to tell. Genotypically the horse is aa, E - , C^cr C, dd, rr, gg, but phenotypically the horse stays Black, or a Smokey Black. Only resulting offspring will show the cremello gene as a palomino or buckskin foal. Foals can be born looking black or charcoal grey and these foals will eventually shed to black. Black x Black cross can produce black or sorrel/chestnut foals. It can also produce palomino foal if the cremello gene is present (see palomino.) Black x Black will never produce bay or brown if the horse matches the black description mentioned above. Brown horses are have the black gene and subtle gene modifiers that cause bay and sorrel colored spots on the muzzle and flank areas. They also tend to fade to bay during the summer time. Brown horses can produce black, brown and sorrel (not addressing the cremello gene).

Homozygous Black horse will never have sorrel/chestnut foals, and will produce black on sorrel/chestnut mares with two black parents. Horses can be homozygous for the black gene even though they are not black; I have a Grullo tobiano stallion that illustrates this. There is a direct red-factor test to determine the genes, see the UC Davis website.

All the rest of the coat colors are additional genes that modify the above two colors (with a few exceptions.)

Grey (aa, ee, cc, dd, rr, G- ), this is a Sorrel/Chestnut horse with the Grey gene) is the gene that dominates everything eventually, and Grey is easy to identify from a roan because a Grey foal is not born grey. When they shed they start turning Grey around the eyes and ears first. Roan horses are born with white hairs mixed with the base coat color and typically have no roan hairs on the head or below the knees.

Palomino (and Cremello/Perlino): (aa, ee, C^cr C, dd, rr, gg ) have one cremello gene turning a Sorrel/Chestnut to palomino and having little or no effect on a black horse in the absence of other gene actions. Palomino x Palomino cross will produce palomino, Sorrel/Chestnut and cremello foals. Palomino foals are usually born a very light palomino and then shed out darker, but every now and then one is born a kind of faded Sorrel/Chestnut color. These foals then shed out the golden palomino check the roots of the mane within two or three months of age. Perlinos and Cremellos have two cremello genes and are also called albino's. These horses are not lethal whites and will not produce lethal whites unless they have a paint/overo background. These horses have light blue eyes that are photo sensitive and I have come to the conclusion they don't see quite as well as a normal horse, almost like they were nearsighted (I own one and have observed several others). Hearing seems to be unaffected, and the foals appear normal and carry a cremello gene, making them 100% palomino and buckskin producers.

Bay (A - , E - , CC, dd, rr, gg) is a black horse with a gene that modifies the body to a dark red/brown color. Bays always have black points, black below the knees, black mane and tails. The agouti (A,- ) gene is responsible for the modification (and I refer to it as the bay modifier.) Bay x Bay crosses can result in Bay, Brown, Black and Sorrel/Chestnut foals. Bays typically are born bay with light colored hair on the legs that becomes black and when they shed out.

Buckskin (A -, E - , C^cr C, dd, rr, gg) it should be easy to tell now that a buckskin is a bay with a cremello gene. It also shows how hard it is to breed all three players, black, bay modifier, and cremello gene to one foal. Buckskin is one of the colors that show some of the subtle gene actions. There are Smutty-buckskins, buttermilk-buckskins, almost-Bay buckskins and all varieties in between. I have not seen many buckskin foals, I assume most are readily identifiable but contact a longtime buckskin breeder if there is doubt. Buckskin x Buckskin crosses result in Sorrel/Chestnut, Palomino, Bay, Black, Buckskin, Cremello, Perlino, and Brown foals. Buckskin-Duns are addressed below.

Dun-factor (aa, ee, CC, D - , rr, gg: this shows a Red Dun) is a family of horses. All horses with a dun-factor gene have a distinctive dorsal stripe down the length of the back. Some horses have faint dorsal or part dorsal but these do not carry the true dun-factor gene. Dun factor is also usually expressed at least some of the following: ear bars and tips, face mask, cobwebing, leg
stripes, and neck and shoulder bars. Grullo is dun-factor on a Black, Dun is dun-factor on a Bay, Red Dun is dun-factor on a sorrel/chestnut. Dun-factor can also be on a Grey horse, but eventually this is covered by the Grey. Dun factor can be present in a homozygous form, and some horses throw only dun-factor foals. Dun x Dun crosses (Bay with dun-factor) can result in Black, Grullo, Bay, Dun, Sorrel, Red Dun foals. Some foals are born with some dun-factor characteristics (faint dorsal and leg stripes), and these shed out within the first year. They will not have the other characteristics of dun-factor. Dun-factor foals are born yellowish, even Grullo, and darken as they shed. (Horses born Charcoal-Grey will shed to black.)

Buckskin-Duns (A - , E - , C^cr C, D - , rr, gg) for this article these horses have both types of dilution gene, Dun-factor and Cremello. (Sometimes this term refers to just duns who are coppery-buckskin with a dorsal.) On sorrel mares these resulting foals can be Sorrel (drat it!), Palomino, Buckskin, Black, Bay, Brown, Grullo, Dun, Red Dun, and are truly desirable horses for color
production.

Roans (aa, ee, CC, dd, R - , gg, shows Red Roan) these horses have a roan gene that turns Black to Blue Roan, Bay to Roan, and Sorrel to Red Roan. Now I will say some people switch around Red Roan to include to Bay Roans, but as they are different, I like to use the same naming pattern as the Dun-Factors for consistency. Also I am referring to the Roans that are true Roan, not the horses that just happen to have some white hairs in the flanks. Rubicano is confused with true Roan. Rubicanos have a 'coon tail' of white baring at the tail head and white hairs in the flanks, some quite strongly. Go Man Go is an excellent example of a horse registered Red Roan, but his tail clearly shows the roaning to be from the Rubicano gene.

The table below is directly from the UC Davis website at www.vgl.ucdavis.edu/~lvmillion

Genetic Formulas and Color Definitions
Genetic Formula	Color
W	White (not addressed)
G	Gray
E, A, CC, dd, gg, ww, toto	Bay
E, aa, CC, dd, gg, ww, toto	Black
ee, aa, CC, dd, gg, ww, toto	Red (sorrel/chestnut)
E, A, CCcr, dd, gg, ww, toto	Buckskin
ee, CCcr, dd, gg, ww, toto	Palomino
CcrCcr	Cremello
E, A, CC, D, gg, ww, toto	Buckskin dun
E, aa, CC, D, gg, ww, toto	Mouse dun (grullo)
ee, CC, D, gg, ww, toto	Red dun
E, A, CC, dd, gg, ww, TO	Bay tobiano
ee, CC, D, gg, ww, TO	Red dun tobiano