Gray Horses

Graying Horses...
ANY color horse can turn Grey if it has the dominant Grey gene. On HWO, it will be noticable a little while after a foal is born. You will start to see a ligher color forming a ring around the eye. After this, the face will start to look whiter. Dapples will then form and the coat will fade out at the horse ages.

Example of White Ring around Eye
- the FIRST stage of Greying

 

 

Color Modifiers - The Gray Factor!

Gray – Gray 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. Determining the Original color of a Grey horse can be tricky as patterns and colors have faded. The only true way to know is thru breeding or genetic testing.

1. extensive depigmentation on the muzzle and around the eye. This is sometimes referred to as "Pinkie" or "Fading Arab Syndrome".

2. Steel/ Iron Grey – Just starting to Grey

3. Dapple Grey – 4 – 12 yrs

4. Flea bitten - This term describes horses that have small red or black (or both) dots on their body - little specs all over their body.

5. White Grey - This term describes horses who have completed the greying process. All pigment in the hair, including that in his mane, tail and legs has been removed. The darkness of the muzzle is just the skin.

6. Rose Grey - term used for horses that have a Bay or Chestnut base coat.

7. Tetrarch Spots - There is no formal name for these unusual spots that appear on Grey horses. (No Picture Yet)

8. Bloody Marks - Blood marks are basically a very large concentration of fleabites in a particular area of the horse, that can enlarge as the horse ages. (No Picture Yet)

Examples of the Stages of Greying to come soon...

Grey Genetics Defined...How to breed a non-greying horse?

Simple Dominance is when there are two alleles at one locus... in which one dominates, or masks, the expression of the other. The allele that "covers up" the other, is known as the Dominant allele. The allele that is "covered up" or "hidden", is called a Recessive allele.

Simple Dominant gene action can be described as on/off switches. If a dominant allele is present, then the switch is set to on. If no dominant allele is present, then the switch can be considered off.

Since only one dominant allele needs to be present to turn a switch "on", it can "hide" the fact that the other allele may be a recessive "off switch" . Therefore, a horse can carry a recessive allele, and not show it.

The Grey coat color in horses, is an excellent example of this Simple Dominant gene action.

Breeding Possibilities:
The grey horse in this example, is Homozygous for the Dominant Grey gene. Both alleles are the dominant allele, known as G. The G alleles turn the "switch" for the grey color to on.

This horse's Genotype can be shown in text as GG.

The Phenotype of this horse... that is, what the horse looks like (the physical "expression" of the grey trait or characteristic) is a grey-colored horse.

The chestnut horse in this example, is Homozygous for the recessive allele g, which would turn the "switch" for the grey color to off.

The Genotype for this horse is gg. Since both alleles are set to off, the horse is not grey.

The Phenotype (or physical appearance) of this horse is not grey since both alleles indicate that grey coloration is turned off.

let's cross these two individuals. The chart shows all four possible combinations of the two alleles that each parent carries... this is what we could expect to see....

This is because the Dominant G allele that produces grey color, overrides or covers up the non-grey color (in this case, a chestnut). It only takes one "on" switch to turn the horse grey. You can't tell by looking at the horses, but all of these offspring in the F1 Generation are carrying a hidden non-grey "off" switch.

Since each of the possible offspring carries one G and one g allele, they are known as heterozygotes.

Now, let's see what happens when we cross two of these offspring together...

Notice the genotypes (the letter designations, of GG, Gg and gg.) Three of the four offspring are grey, carrying at least one G allele that turns the grey switch to on. However, one foal received two gg "off" switches... and with no G "on" switch to dominate, or override it... the resulting offspring came out non-grey. (In this case, chestnut.)

Based on the chart, we can establish relative "probabilities" to obtain grey color from this type of mating.
- 25% Homozygous Grey (GG)
- 50% Heterozygous Grey (Gg)
- 25% Homozygous Non-Grey (gg)

It should be noted that the grey gene in horses, is considered to be dominant to all other colors. If the horse possesses a dominant G allele at the "G" locus, the horse will be grey. The underlying color doesn't matter, and grey can occur on chestnut, bay, dun, palomino, pinto, appaloosa and other colors. Of course, where there might be white markings on the horse, you won't be able to tell the horse is grey in those places.

Now, let's cross a Heterozygous Grey (Gg) to a Homozygous Non-Grey (gg).
Based on the chart, the following probabilities can be established:

- 50% Heterozygous Grey (Gg)
- 50% Homozygous Non-Grey (gg)

Based on this information, you should be able to easily chart out the probable colors of offspring of any single Simple Dominant gene.