THE A, B, C, D & E"S OF EQUINE COLOR GENETICS

THE COLOR BLACK

Much research and literature has been written on the subject of equine color genetics. This small dissertation is not meant to be a scientific paper on the subject.

All horses tend to have either black or red as a base coat. Black is a basic color for horses .Black is also a recessive gene which means that the gene can be overwritten by any number of other genetic factors. The best indicator of the color black is the lower leg. The black color, considered a base color, is caused by several alleles. Some horses may have the black gene and may actually look more non-black. However, genetically they are, indeed, black.

Black horses have black points - primarily black manes and tails. Other points are present but these points are the most reliable. Most black horses and all horses in general fade in the sunlight. As a result the horse can actually look brown red or grey. If exposed to sunlight for a period of time, the average black horse will turn to a brownish black or reddish horse in color on the mane and points. However, when the sun is not so intense the black color re-emerges. The color black is actually protective since black horses do not tend to get skin cancers or tumors (melanomas ) as do grey horses. In previous times black and darker colors were considered to be hardier animals.

Dominant genes are described with capital letters such as A, B, C, D, or E and recessive genes are described with small letters (a,b,c,d,e). Theoretically, a dominant gene prevails. However, this is theoretical and not absolute. The most important genes will be considered here. All genes are operational at all times. The total picture of genetic expression is called phenotypye. In other words, all these genes are working at the same time. A homozygous gene of one type does not guarantee a black horse when breeding. See below.

There are five basic genes related to color :

A-the Agouti gene which allows black to be seen when recessive(aa)

B-black or brown gene

C-colored restriction

D-dense color or dilution

E-the extension gene for color from the base of the hair to the tip of the hair

The A gene: The letter A stands for Agouti. When recessive the non- Agouti gene (aa ) causes the hair color to be black and pigmented from base to tip. This gene must be present for the color black to show or else the color black will be hidden by other colors. We don’t want a dominant A gene as the hair pigment would be spotty.

The B gene: This controls the color black but is not the only gene affecting the color black. The gene depending upon its expression in the individual horse will create either black or bay.

The C gene: This gene causes color restriction i.e. the areas restricted to color or by color-slightly confusing without the remainder of the information below. It determines how and much color is expressed or not. Simply put, the gene expression will lighten any color that is the base color.

The D gene: This gene causes color density or dilution. Dominance or recessiveness of this gene will create a deep or diluted coloration. Basically, a dun horse is created if expressed

The E gene: "E" stands for extension for its effect on the eumelanin or black pigment of the horse. Large letter E equals a dominant gene while a small letter equals a recessive gene. Therefore, we can have a EE black which is homozygous or an Ee black which is heterozygous black. Both will show black as the color if combined with the Agouti aa gene. Let me state that again-both homozygous and heterozygous expression of the E gene will produce a black horse. You need the non Aguoti gene to express black. Homozygous is not enough to produce black by itself.

Horses that are homozygous for black may be homozygous dominant or recessive. One homozygous combination of either recessive or dominant genes does not control the final outcome of a breeding. Many potential breeders look only to the stallion genetics. The genetics of the mare must be considered also. Black bred with black will give a black foal provided at least one parent is dominant E in one gene only.

Alleles are "an alternative form of a gene that can occupy a particular chromosomal locus" or location. Alleles are basically one half of a gene. As a result there are usually two alleles on each chromosome. If a horse has two alleles on the chromosome that horse is considered "homozygous" - or possessing a pair of alleles for that trait. If a horse has only one allele then that horse is considered "heterozygous" -or possessing only a single allele. Not every allele "counts" or is expressed as the terminology is used. If you have the allele you still must have the genotype or the entire genetic constitution to cause black. Some alleles are recessive and some are dominant.

There are factors which modify or change the color black. Indeed, there are several shades of black. There is a jet black, raven black, plain black, summer black and entrepelado (essentially a roan black). Jet black horses never fade in the summer and others become a flatter color but are still black The color black can be a soft velvety black to a flat black.

The Spanish have several terms for the color black.

Jet black is called negro azabache with a black color similar to a shining mineral.

Coal black is called negro morcillo(or morcilla if a mare ) which is a less intense black color than jet black. Many claim that it is similar to a ripe blackberry.

Tarry or ill-dyed black(negro peceño or mal teñido) have a color of pitch and/reddish highlights.

Roan black or entrepelado

There is an ancient Spanish proverb that states that "A whole coloured black is sought by many and found by few." Therefore, it is normal to find some head markings on black horses.

The best and easiest way to get black is to breed to or to buy a black horse. Contrary to statements on some websites that the color black takes years to manifest itself, our experience is that the color becomes visible and known within six months, if not sooner. You don't have to wait years to have a black horse.

Call Poplar Ridge Andalusians for your black Andalusian -the Pura Raza Espanola (PRE ) dream horse! We have all types of black and some bay horses. Black is magnificent, elegant and beautiful! Our horses are all healthy and of exceptional quality and breeding. Call us and see for yourself!