Colour testing

Posted on June 14, 2017 at 3:10 AM

I've had nearly all of the ponies colour tested now, their results are on each pony's profiles. This helps clarify what the ponies colours actually are, and helps predict the colour possibilties for future foals. 

Here's some information from the Practical Horse Genetics colour test returns, that may help make the letters make a bit more sense.

E/e = extension - in it's simplest form, this is the basic red or black base colour every horse has.

"Most horses are chestnut, black or bay/brown. Many other unusual coat colours come about when these basic colours are modified. Just two genes control these basic coat colours.

The extension gene (MC1R) controls the production of red pigment (i.e. to produce the chestnut coat colour) vs black pigment (i.e. to produce black or bay/brown coat colours). If your horse or pony is bay/brown or black, you will need to use genetic testing to determine whether they have one vs two copies of the version of this gene that produces black pigment."

A/a = agouti - a basic explanation is this is what restricts black to the points (makes a black horse bay.

"Agouti (ASIP) is the bay factor gene, which can restrict black pigment to the points. If your horse is chestnut or a colour based on chestnut such as palomino, you will need to use genetic testing to find out which versions of this gene your horse has inherited. If your horse is bay or a colour based on bay such as buckskin or bay silver, you will need to use genetic testign to find out how many copies of this gene your horse has inherited."

D/d (d1/d2) = dun (and non-dun / countershading) is a modifier that dilutes the coat colour, and causes dun factor - dorsal stripes, masks / cob-webbing, leg and shoulder barring etc.

"The dun coat colour in horses dilutes both red and black pigment by limiting the distribution of pigment granules to a small part of the hair shaft. This dilution is accompanied by darker undiluted markings that can include a dorsal stripe (most commonly), leg barring, dark ear tips, and shoulder bars. The face and points of dun horses are also usually darker than their bodies.

In contrast, the coat colour and markings associated with d1 reflect what is commonly referred to as counter-shading.These horses are expected to have a dorsal stripe and possibly other markings usually associated with dun. Horses that are positive for d1 but not dun are NOT dun."

Gr/gr = grey

"Horses and ponies that carry the gene variant that causes greying with age are special. They go through a beautiful range of shades on their way to becoming completely white or flea-bitten grey, but they also have a high risk of developing melanoma.

Genetic testing can confirm whether your horse has the gene variant that causes greying with age and increases susceptibility to melanoma."

Highland Ponies can also carry the silver gene, but as we don't have any silvers in Australia, i haven't bothered testing for it. Purebred Highlands don't carry any other modifying genes (cream / pearl / champagne) or any of the white pattern genes.  

Our 2017 partbred colt foal was tested for white pattern genes, as his dam is a Paint Horse, who clearly exhibits white patterning. Tain was found to carry one copy each of both overo and sabino - which is why he looks white. He's basically on big white spot, with his bay base-colour restricted to his ears and a few small patches on his body. 

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