White face and leg markings

One of the most common types of patterns seen on horses are face and leg markings.  There's also a bit of a debate surrounding these markings.  Some say that Sabino is present with any face/leg marking, while others say that many are "birthmarks" and that they just happen.

I'm not sure a study has ever been done to determine who is correct.  We do know that face and leg markings are inherited, and that sabino (which is actually a group of genes) causes certain characteristics to be seen on face and leg markings.  We also know that other genes affect face and leg markings as well, such as splash and Overo (OLWS). I think that much of the sabino debate is due to people wanting their horse to have some "cool" pattern, and the recent acceptance of excessive white in many breeds from Arabians and Thoroughbreds to the white rules in AQHA.

Certain types and locations of these markings are considered normal.  Socks, blazes, stars, and stockings are all easily accepted markings on a "solid" horse.  Then you have something like this filly shows.  Her blaze is irregular, and even has a hole in one area of it, and a displaced section of white on the opposite side.  This is Soliloquy, a Stonewall Sport Horse filly whose name I usually shorten to Soli.  Her dam has both sabino and splash (black mare shown below), while her sire carries sabino.  Soli's markings show mostly traits of sabino, but there are a few signs that show she is also carrying splash.

Ever wonder how to tell the difference?

Sabino markings tend to be pointy.  Sharp areas on blazes and socks that point towards the belly.  Also, white on the lower lip is a big indicator of sabino.  The chestnut shown below has classic sharp sections around his nostrils, and the black has obvious white on his lower lip.  Both horses are suspected to have minimum sabino.

For many people these markings look perfectly normal, and they are.  But splash tends to cause face markings that are heavier on the bottom, and often rounded or apron shaped.  Here are a few examples of splash blazes.

Granted, both mares above are giveaways because of those blue eyes - which is most often a trait of splash.  You can also see though, that while the blazes are very different, both are heavier on the bottom, and are mostly smooth shaped.  Below is a mare with a large face marking showing traits of both sabino and splash.

This is Jinx, one of my foundation Sugarbush mares.  On her left side (the first image) she shows classic sabino signs, including the blaze that goes under the lip, and a few subtle hints of splash, such as the width of the blaze and rounded nature of it.  On her right (second image) she has a "dipped in paint" appearance that is often seen with splash, and is always present when splash goes under the chin.  Also notice the sharp pointy effect around her eye, and in her cheek area?  Those are signs of sabino.  Jinx is a good example of how common markings can give us clues as to minimal white patterns carried by a horse.

Then there are leg markings.  Sabino leg markings are pointy (see a pattern here?) and usually are higher towards the belly.  The only horse I have that shows this carries both sabino and splash, but I think you can get the idea.  Yes, she's also very pregnant in this picture.

On the other hand, splash markings tend to be even on all 4 legs, or close to it.  The seal bay mare shown below has even socks, but they all point backwards.  This is occassionally seen on both splash and sabino horses.  With the prevalence of sabino in appaloosas, it's reasonable to assume from the sharp tops of her socks that the seal bay mare also carries sabino in addition to her splash.

On the other hand, not all splash horses have 4 white legs.  Arden, shown below, only has 3 white socks, which are close, but not perfectly even.  She shows no obvious signs of sabino, but again, due to the breed, we can't rule it out.

But what about horses who don't have that much white?  Here's a mare with no leg markings, and only a small amount of white on her forehead:

Her appaloosa colored colt has almost the exact same white marking as well, and neither has any leg markings.  Could these be from embryonic development?  In other words a birth mark?  Science has yet to prove it, although neither she, nor the foal show signs of additional effects of other white patterns.

As for those "other effects" well, genes like sabino, splash and frame (commonly called frame white, or overo) have an effect on other white patterns.  These are called "enhancer genes".  It is a well documented fact that horses with excessive white face and leg markings tend to show more white in their patterns as well, both pinto and appaloosa patterns.

Base coat color also plays a role.  Dominant extension (E) is a suppressor of white patterns, while recessive extension (e) is an enhancer.  What does that mean?  Well, a horse that is Ee will have a smaller blanket then a horse that is ee, and a horse that is EE will have an even smaller blanket then the heterozygote.  Agouti is an enhancer gene, and it's effects have been documented even when the gene is hidden.  A horse with the genome ee AA will have a larger pattern then a horse with the genome ee aa.  To make it somewhat easy to remember, we often say that black supresses the most, then bay (a little suppression and a little enhancing), then chestnut. 

These suppressors and enhancers will become important when I talk about appaloosa color genetics.  There are MANY genes that have a suppression or enhancing role in color, and not all of them are known.  In some cases we know that certain family lines, or breeds have "suppressors" but we don't know exactly what causes it. 

This is why genetics tends to get so confusing.  There's so much going on at the same time, and genes can have multiple roles.  In many cases people ignore the supression and enhancing traits, and simply work on the basic genetics of the coat color, but if you want to breed for a very specific pattern (such as minimal paints, or leopard appaloosas) then these additional effects must be taken into consideration.

Many of the same genes that cause face and leg white markings can also cause pinto patterns with a "louder" expression.  Splash is most commonly seen as face and leg white, but is most commonly associated with high chrome horses.  Frame is ususally expressed as a pinto pattern, but can "hide" in face and leg markings only.  These pinto patterns being expressed as only "normal" white markings are often refered to as "minimal" (insert type of pattern).  Such as a minimal splash, or minimal frame.

Now, for your test......

What pattern genes would you suspect this foal of having?