Black Based Horses

Black Based Horses...

Black Base - The control for Black is located at the Extension locus and is dominant at that locus. Black horses are not capable of producing Bay foals unless the mate is a Bay or a Chestnut masking Agouti. Black at the Extension locus is symbolized by "E", since it is dominant. Chestnut is also located at the Extension but it is recessive so it's symbolized by "e".

· EE means the horse is genetically (homozygous) and physically Black*
· Ee means the horse is genetically (heterozygous) and physically Black*
· ee means the horse is genetically and physically Chestnut*

*These horses are physically Black or Chestnut when there are no dilution or modifiying genes present.

In addition to the Horse's BASE color, it may also
have white patterns, Color Modifiers, and other
unexplained colors/patterns.

Black Based Horses Color Dilutes & Modifiers

Color Dilutes:

A. Dun Dilutes – Grulla/ Grullo

B. Cream Dilutes – Smokey Black (one cream gene) Smokey Cream (two cream genes)

C. Silver Dilutes – Silver Dapple (Black or Chocolate Silver)

D. Champagne Dilutes - Classic Champagne

E. Roan Patterns - Black Roan/ Blue Roan

Bay Base - Bay is actually a Black horse with a restrictor or modifying type gene at the Agouti Locus. There are many different terms used when describing the different shades of Bay. The most popular being Black Bay, Mahogany Bay, Standard Bay, Blood Bay and Light Bay. All Bay horses will have a red body, ranging from light to dark, with black legs from the hoof to the knee and hock and sometimes extending above the knee and hock. The mane and tail will also be black. In the case of "Wild" Bay, the black points are restricted lower on the legs, to varying degrees. The Wild-Type allele A+ expresses itself in that the points (particularly the lower legs) tend to have less black than regular bay color. The black may extend only up to around the pasterns, and possibly onto the cannon, but portions of the cannon and lower leg are mixed with red pigmentation rather than being mostly solid black.

The Agouti Locus

The Agouti (A) locus controls where on the horse the black pigment shows up, (if the horse is capable of producing black pigment). The alleles involved here are a dominant A and a recessive a. The dominant A allele causes the black pigment to be restricted to the horse's Points.
Points of the horse for purposes of color determination include:
- Lower Legs
- Mane, Tail and Forelock
- Muzzle
- Eartips

The recessive a allele, does nothing. Therefore: AA or Aa is Bay and aa is Black.

Together, the E and A loci determine:

- whether or not a horse can produce black pigment
- where on the body the black pigment appears
- What happens at E may cover up what happens at A (even though a locus doesn't have any visible effect... doesn't mean the horse isn't carrying any alleles at that locus... they most certainly are! But those alleles won't be able to show themselves, until the right conditions occur in a later generation.)

If you study the chart to the Left, you'll note that whenever a horse is ee-- recessive chestnut, it doesn't matter what alleles are present at A. Whether A is homozygous, heterozygous, dominant or recessive alleles, the horse remains Chestnut. This is why, when you breed two chestnuts together, you always get some form of chestnut.

For black color to show itself, the horse has to be "genetically black" at the E locus (carry at least one dominant E allele) ... AND the horse must also be recessive aa.

This may help to explain why black color can be so elusive to breed for in horses, and why it can suddenly pop up unexpectedly.

You can Easily tell if a horse is showing the BAY gene by looking at the horse's ears, even if no other black areas are shown due to Splash markings or other markings that may hide the BAY coloration. If the ears are darker at the tips, then the horse is expressing the BAY Gene.

Dilutes on Bay Horses:

A. Dun Dilutes – Bay Dun/ Zebra Dun

B. Cream Dilutes – Buckskin (one cream gene)
Perlino (two cream genes)

C. Silver Dilutes – Silver Bay

D. Champagne Dilutes - Amber Champagne

E. Roan Patterns - Bay Roan/ Red Roan

Color Modifiers

A. Bay – Black Base with a restrictor gene

B. Grey – Grey is an ongoing process of depigmentation of the colored hairs. Grey slowly removes the pigment from the base color. Grey is dominant, meaning, the horse must have at least one Grey parent to be Grey and if a horse has Grey it will be shown physically. All Grey horses have a base pigment of either red or black and depending on what other genes are present all Grey horses were another color at birth. For MORE on GREY please visit the Grey Page.

C. Flaxen - Flaxen is a modifier that affects the mane and tail, causing it to become a white to cream color.

D. Sooty/ Smutty - It acts on both red and black based horses by darkening the color or certain areas of the horse. It varies in extent from minimal to extensive and has a many different expressions.
Sooty - can cause dapples, it can cause individual black hairs, it can cause a darker shade along the topline and it can also darken the animal in a uniform manner. Sooty is most concentrated along the top of the horse, like a bucket of ash was poured from head to tail.

E. Mealy/ Pangare - The effects of this modifier are seen along the underside of the horse. In the "soft" parts, or on the muzzle, behind the elbows, in the flanks, on the buttock, above or around the eyes and along the belly. The color of these areas depend on the color of the horse but usually range from white to a light tan.