Albinism in Horses

To follow up with the promised post after the last one, I of course have to talk about albinism in horses. To recap, albino is when there is no pigment in the skin; all genes that control color are off.

There are quite a few curiosities on the subject, including a simple fact that will surprise you: albinism has never ever been proven in horses.

While you may be able to Google quite a few images of horses that appear albino, there has never been a case in which they weren't able to prove it was something else. The horses above came up in the search, as well as the ones below.

As mentioned in the last post, red eyes only sometimes indicate albino, and there are several other things besides that would. However, with horses, there is no picture I can find of a horse with red eyes that doesn't look photo shopped, or when you look close up are actually blue eyes surrounded by pink skin.

According to various sources, blue eyes in horses is not exactly lack of pigment, and is as close to non-pigmented eyes as you can get, but again there isn't no pigment.

The most commonly mistaken color for albino is cremello, because of the very light-colored skin that often is pink with blue eyes. However, using the method of deciphering albino as in the last post, albino has no base color, and there is no pigment behind it. Cremello is a chestnut horse with two cream genes, so it would indeed have some pigment. Other double-cream horses (perlino, smoky cream) may be categorized among cremello in being mistaken for albino.
If you were to take the tiniest bit of red paint, and then add a dose of white, it makes pink. If you add even more white, it becomes light pink. Even if you keep adding white to the original red, the paint will never be truly white, no matter how much you put in.

One of the closest things to albino scientifically is dominant white. Dominant white is considered to be a white-spotting genes, along with patterns such as tobiano and frame overo. The main difference with dominant white is that it often shows up as one, huge spot, entirely covering the body and blotting out the under color. Did you notice that last sentence? 'The under color'. There is a color under there that they can pass on.

Dominant white can be expressed in many different ways, even within each specific mutation. It isn't always predictable, and because of that it isn't a fool-proof way to describe as albino. It seems like most of the time, it leaves the eyes their original brown color, although there are some cases of white. That would depend on the specific mutation.

Fully-expressed sabino is similar to dominant white, except that sabino never causes blue eyes, leaving the eyes dark.

So, I guess the underlying question is: why? Why has albino never been proven in horses? Why would horses be the exception?

Albino means there is no pigment whatsoever, and they never have any color to pass on. With all these genes, the horse also has a color underneath. The only way for a horse to be albino would be that somehow, the gene that causes pigment (extension) wouldn't be working.

Extension is the only gene that causes pigment. All the rest of the genes I speak of are simply instructions, or a way to lighten what was already there. Isn't that interesting?

For albino to happen, extension would have to find a way to not work. Because it is a dominant gene, one or two copies produces black pigment. In recessive form, it causes red pigment. That doesn't leave any option open for no pigment, see?

In the whole history of horses, we haven't found a way for it not work as of yet. Albino hasn't happened yet, that doesn't mean it can't. Extension would have to find a way to be missing entirely from the genome, but how when both parents have it boggles my mind. Colors, and the way they work, and the way we percieve them is constantly changing.

Horse Color Genetics: Champagne

Review: E= black, A=bay, G=gray, CR=cream, D=dun, T=tobiano, F=flaxen, Z=silver, O=overo, SPL=splashed white, SB1=sabino, LP=leapord complex (appaloosa), R=roan.

I didn't even know this color existed until I started researching genetics; it is very rare. Please don't confuse champagne with dun or other geneticly-modifying coat lighteners, or dilution gene, like the cream gene.

Champagne is basically a coat lightener, in the extreme. It makes the tone of the color very different from what it would be if it didn't have this modifier. CH is the abbreviation for champagne.
Generally, champagne's are very shiny, and have very unusual colored eyes that are hazel, but they may have been born blue and turned darker with age. The champagne gene also gives unusual freckling to the skin, which won't show through the coat but may show on the skin around the eyes, and will show in their private parts.

Here are some different kinds of champagne:

This horse is called a 'classic champagne'. It is black, with the champagne-diluting gene. It is hard to believe that the under color is black, but it is.

Here is what would be a bay, but with the CH gene. This is called 'amber champagne'. See how it makes the black of the mane and tail just a tiny bit lighter? On a bay, it looks similar to what the dun or cream gene might do.

Here is a chestnut champagne, or gold  champagne. They can sometimes be confused with palomino's, but they will have the tell-tale hazel eyes and freckled skin.

 Below is a gold cream, a palomino with the CH gene. It can easily also be confused with palomino or even cremello, but all those signs will still be there. CH is a like a super-diluter.

One very unusual color is cremello (CRCR) with CH. It looks like a cremello, but may contain that champagne gene. If you don't know what the parents are, then you won't be able to know if it has that CH gene. There is a genetic test available somewhere. I don't know if the freckles will show or not.

There actually is a champagne horse registry for champagne-colored horses here. Champagne is a simple dominant, and may override other genetic modifiers like dun; the champagne color goes on top of the dun and may lighten the markings.
Like other modifiers, it can be paired with nearly any other modifier, but may be less apparent.

Horse Color Genetics: Dun

Review: E=black, A=bay, G=gray, C=cream.

The next color is dun. What is dun? A dun horse is a horse that receives special markings through its genetic code. Dun horses always posses a very clear dorsal stripe, or a black stripe that runs across their spine. Dun horses commonly have faint stripes on their legs, and sometimes a faint dark shading across their shoulder blade. Duns always have a darker mane and tail than their base coat; whether the mane and tail is black depends on whether they also have an E gene. The only exception to this rule is a palomino dun, whose mane and tail will still be white, or cremello dun. In the second picture, the horse has a dark bar along his shoulder; some duns may or may not have this. There are lots of duns with dorsal stripes below!

The dun gene, or D, is a simple dominant, meaning that whether the horse is homozygous dominant or heterozygous, it will effect the horse in the same way. When I say almost, I mean that depending on the base coat, it will vary. It does not necessarily effect different colors in the same way; the original color without the D gene will still show through.

The D gene has a lightening effect on any coat. Usually combined with a chestnut horse (ee, aa), black horse (E?, aa), or a bay horse (E?, A?), the base coat will show through, but if it is a bay horse (E?, A?), the rules of how it goes can be confusing. The dun gene pushes any existing black to the edges, similar to to the A gene; however, it usually leaves the face and legs darker.

There are several different technical terms within dun, depending on what the underlying coat is. The most common color is 'classic dun', or sometimes 'bay dun' or just 'dun'. Bay dun (E?, A?, D?), when the D gene is added, dilutes the dun to a very light color. This color is usually the same or nearly the same as a buckskin, although there is a clear difference; buckskin by itself usually doesn't have the dorsal stripe. The horse below looks an awful lot like a buckskin, right? But he is actually a bay dun. He is so cute!

To make matters more confusing, there is such thing as a buckskin dun. This horse's code will look something like this: E?, A?, Cc, D?. This means that it was a bay, then diluted to buckskin, then diluted further to a dun. Buckskin bay, or dunskin, is more of a bright golden, while a bay dun may be slightly duller, more brown.  If you aren't sure, you may need to have your horse genetically tested. If there is ever any question as to which, if you know about the parents that could help. Remember: buckskin is the result of a bay with a cream gene. If there is no cream gene in either of the parents, then you know it is a bay dun. See how much more golden he is? Much less brown.

Chestnut dun, or red dun, turns the horse's chestnut coat to a lighter, more rosy shade. Remember, chestnut horses are recessive black, so the mane and tail are not black. They will turn a darker shade than main coat though. A clear dorsal stripe still shows, but it will probably be dark red instead of black.

Black dun horses are called grullo (or grulla (pronounced Grew-yo, or Grew-ya) depending on who you talk to). Grullo horses are black horses with the dun dilute; they turn almost a blue roan color, or sort of grayish with a dark head and dun characteristics. 

Dun can also effect horses with other color genes, including pinto, roan, palomino, among others. I won't post pictures of them all; basically dun will always lighten a color, and add a dorsal stripe. The horse below is a tobiano dun.

There is something else called 'countershading' that can sometimes be confused with the D gene. Countershading looks like a dorsal stripe, but it won't be very clear, or might go halfway up the back, or may be a thicker line. A dorsal stripe should be very clear and straight, like someone took a juicy dark marker and ran it up their back. If the stripe is kind of thick with not clear edges, then it is countershading. The horse below is so close! But....it isn't complete. He is not a dun. The stripe isn't clear, and it doesn't go up the back all the way.

Horse Color Genetics: Cream

Review: E = black, A=bay, G=gray.  The next color gene is the cream gene. This gene does a lot of different things, depending on whether the horse inherits one or two of this gene. This fact is called "incomplete dominant", which means that the cream gene will effect any color, but what it will do depends on whether the horse is homozygous cream or heterozygous cream. Cream creates palomino, cremello, perlino, smoky black, smoky cream, and buckskin, depending on different combinations. I will start with palomino because it is the easiest to understand.

A palomino is a chestnut horse with one cream gene. The cream gene dilutes the chestnut into a lighter color. But for a palomino to happen, it has to have inherited only one cream gene (heterozygous; heterozygous means there is only one dominant in that particular gene). If it inherits two cream genes, chestnut is diluted even further to produce cremello. Cremello looks like an albino, but it is different. Cremello is a cream color with blue eyes.

Backing back up to the palomino; palomino is an easy horse to breed. If you breed a Cremello horse (cremello's have two dominant cream genes) with a chestnut (think blank slate), you end up with a horse that inherits one dominant cream gene from the cremello parent. Therefore making palomino.

So the horse above's genetic code would be: ee, a?, CRcr. No black, but it could possibly carry one or two bay genes but you wouldn't know because there is no black to push out. Now if it was like this, ee, a?, CRCR, then the horse would look like this:

Looks an awful lot like an albino, right? But it has blue eyes(this indicates there is pigment in the eyes; albino animals lack any pigment whatsoever) and the coat color is more cream, not white. If you compare this horse to the gray horse below, the gray looks even more white than the cremello. I know this is a gray because of the dark skin around the muzzle.

Perlino is another color that is very similar to cremello, and you may not be able to tell them apart. Again, perlino requires two dominant cream genes, but also a black gene and a bay gene. These are more rare, because you have to have that combination. Usually perlino's have slightly darker manes and tails, but they will have blue eyes like a cremello. Cremello's, perlino's, and smoky creams are all born with this color. The horse below is a more obvious perlino:

Smoky black and smoky cream are rather rare, simply because most people may or may not know that they have it. Smoky black is a black horse (at least one black, or E gene), that has only one dominant cream gene (I'll call it C from now on). There is barely any difference between black and smoky black, other than maybe the tiniest lightening. The horse below also carries a silver gene that lightens its mane and tail, so if you could ignore that for now, please do. It almost looks more like a dark bay, and the lighting is kind of weird, but you get the idea.

Smoky cream is a horse with at least one dominant E gene (black) and two dominant C genes. If it had only one C gene it would be smoky black; if it had no dominant E genes then it would be cremello. The horse below is advertised as smoky cream. It looks the same as cremello and perlino, though! You would really need to have your horse genetically tested to really be able to determine. It also looks slightly pregnant, or has been pregnant....

The last color C gene can make is buckskin. Buckskin is also a complicated color, but I will do my best. To make a buckskin, there must be at least one dominant E gene, at least one dominant A gene, and only one dominant C gene. If there are two dominant C genes, then it is perlino. There could be two dominant E genes or two dominant A genes, but there has to be only one cream gene.
Another thing you must understand is the difference between buckskin and dun. Genetically, they are completely different, but they look very similar. Buckskin is a golden color with a black mane and tail (remember, the A gene pushes existing black away to the edges), while dun horses can be almost any color with certain markings. Dun is not any particular color, but dun and buckskin are often mistaken for one another.

People who are familiar with horses will know what I mean when I say that duns always have a very clear dorsal stripe and sometimes striping on the legs, like a zebra. The horse above is a buckskin because there is no dorsal stripe. Think Spirit; he has a black stripe along his back. An example of what the horse above's genetic code could be: Ee, AA, Cc. Or EE, AA, Cc. Or Ee, Aa, Cc. Or EE, Aa, Cc. get the idea? It could never be ee, aa, Cc. That makes palomino; it has to have at least one E and one A.