A Note about Sugarbush Draft Horses

I see it over and over again, and no matter how many times it's said, it's still wrong. "Sugarbush Drafts are just an Appaloosa Draft Cross". Uh.... no. The Sugarbush Draft Horse was a breed created many years ago in Ohio. While the initial cross was made using Percherons to Appaloosas, in the many generations following, the breed has been solidified into a consistent type. Saying these horses are "just" a draft cross makes as much sense as saying that AQHA horses are "just" a Thoroughbred cross, American Cream Drafts are "just" a dilute Belgian, or that Morgans are "just" a grade.

Tuesday, July 20, 2010

Coat color modifiers

Ok, so we have the basics of a horse's coat colors:  Extension of black (E), Agouti (A), Creme (CR), Dun (D), Grey (G), Champagne (CH), Pearl (PRL) and Silver (Z).  Combining these genes makes up what most people call a horse's base color.

Now, lets talk about a few color modifiers!

Now, these traits are not "genes".  A gene is a sequence of DNA that produces a protein, and that protein has an effect.  Head hurt now?  Let me make that easier.  A "gene" is a single thing that does a single job.  Extension is a GENE.  It makes black pigment, or when homozygous recessive, it has no effect (red pigment is always produced).  A "trait" is a larger concept, and refers to the phenotype (appearance) of the horse.  The black TRAIT is caused by a single gene, where the shade of a horse's color is a trait caused by a bunch of genes working together.  While both are traits, not both are genes.

An analogy to help make the concept clear:  A car is an vehicle, but not all vehicles are cars - some are trucks, some are motorcycles.

So, coat color modifiers come in groups.  In most cases we don't have the genetics mapped out yet, but we can follow their phenotypical expressions (horses that look like this, and how they pass it to their offspring).

The first, is Sooty.  Sooty is most likely caused by a handful of genes working together.  Because of this, we don't have a definitive letter to use to describe it, although some people use "STY" when talking about this group.

Also, the thing to keep in mind, is when you talk about a group of genes that result in a specific trait (a polygenic trait is the technical term) is that there will be variations of expression.  With most genes there are 2, or maybe 3 options.  The horse is black based, or its not (2 phenotypes as found with simple dominant genes).  The horse is chestnut, palomino, or cremello (3 phenotypes as found with incompletely dominant genes).  With these polygenic traits, there is a whole range of options.

A horse can be a little sooty, mostly sooty, very sooty, or somewhere in between.  So, with that in mind, you have to accept that the level of expression of these traits varies because of genes we haven't located yet, and discussing this is beyond the realm of currently known science!  Exciting isn't it?

Ok, I'm a dork.  It's true.

So, sooty makes dark counter shading on horses.  This would be areas of dark pigment in the body color that starts at the top (spine) and progresses down the horse's side (usually).  Here is a good example
In other cases, it starts at the legs, and works its way up, like in this mustang shown below.
What is interesting to me, is that sooty is most often seen on red pigment.  It is very apparent on palomino and buckskin horses (notice that both horses above are palomino).  With so little research on this trait, we can do as much speculations as we want to.  Some people have suggested that this is a resurgence of a primitive trait, others that it's similar to a birthmark and caused by factors during uterine development.

Sooty is important, because what ever causes it, in some cases it alters a horse's color drastically, making it appear to have a different genome then it does.  Here is a picture of my sooty mare, Hex:
And yes, that cute little black baby there is Scorch at a couple of weeks old.  But you can see how Hex's neck and shoulder show markings very similar to those seen in dun? My theory is that top down sooty markings may be an alternate dun allele.  From cob webbing (seen both with sooty, and with Dun) to marbling, and shoulder markings the dun and sooty traits have a lot of similarities.  We won't be sure though, until the gene or genes are actually studied and mapped.  Again, the dun relation is completely my own hypothesis.

Now, the next coat modifier is Pangare.  This trait lightens the under belly, armpits, rump and muzzle of a horse.  This horse is a great and extreme example of pangare.
Pangare is common in Belgian drafts.  Other breeds have it as well, but most people I have met think of Belgians when they see this coloring.  Interestingly, it has been argued that seal bay is really sooty and pangare on bay.  So far science doesn't agree, but the work behind the discovery of the At (seal bay) allele is well...not as readily available as most of us would like.  In other words, we want to know that a discovery can be repeated before science accepts it as hard fact.

And, all those quarter horse people out there, please forgive me.  With most stock horse breeds, it is commonly accepted that sorrel is a light version of chestnut.  In draft breeds it is accepted that sorrel is chestnut with pangare, like the horse above.  You can have many shades of "sorrel" such as honey sorrel, or blonde sorrel, but with out the light markings, a horse is just a chestnut.  When I refer to a sorrel horse, I am most often referring to a horse with pangare.

Through out most of the genes we have discussed, I have references shade quite a bit.  Shade affects any horse's color.  From dark blacks to light blacks....

Such as Jinx, my homozygous black mare, shown sun faded and in her "dark" state above.  She's never a true dark black, but she's still genetically EEaa.  Jinx is a perfect example of a "pale black" horse.  Her shade is light, but her color is black.  All colors are affected by shade, and sometimes we give names to the various shades of the same color.

There are many other traits besides sooty, pangare, and shade.  Most have not yet been studied.  DNA maping is still a relatively new science, and while progress is being made in leaps and bounds, there is still so much more to do.  These coat color modifiers are often the cause for people's confusion on their own horse's color.  Just imagine how the owners of the above palominos felt trying to explain their horse's color to people!  The genetics I have talked about in the last few days are the basis of a horse's base coat color, in all their magnificence.  When you mix and match the genetic options, you can have so many different outcomes.

Now, there's still more!  Base color is one thing, but what so many people love, are the patterns.  From pinto genes to appaloosa genes, with some other white pattern genes thrown in to make it interesting, I'll start covering pattern type genes.  How they work, what they look like, and how they are inherited.  I'll be honest, the pinto genes (Tobaino, OLWS, and the sabinos) are not my strong point, so feel free to correct me on those, and share links to good information in the comments.

15 comments:

  1. :-)
    I love learning new things.
    So, am I correct in saying my haffies are pangare...or do I say they have the pangare coloring or pangare modifier?

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  2. To be technically correct, they are chestnut with pangare. I believe that in their case sorrel is also correct. Although, Sorrel is a subjective term depending upon the breed of horse, in my mind a horse that is ee P? is sorrel (because then sorrel is genetically different then chestnut).

    But if you say they have Pangare that is also correct, because it's refering to one gene, just as one could say they have a "champagne horse"... doesn't tell you the base color, but explains that single trait.

    Did that help you any?

    I have been notified to appear for jury selection today, so responses will be delayed more then normal. Hopefully I get picked to be on the jury. I've always wanted to do jury duty, but as soon as news of my education gets out, I'm always kicked out the door. Wish me luck!

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  3. Thanks for posting color genetic info. I must admit it's all very confusing to me, however the more I read/learn the more it sinks in. Have you thought about tagging your genetic posts? New readers/re-readers would have them all linked together then. Just a thought :)

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  4. I have thought about that Aurora, and I've been piddling around with options to find an easy way to make it easy to find. I'm not the most technically savvy person in the world!

    And, I failed at jury duty. Took me longer to get dressed and drive there (a mile away) then to be dismissed! I have always wanted to serve on a jury, and usually my medical background, previous jobs (hospital work, as a lab tech) or education got me eliminated. Today, it was simply bad luck.

    Juries are selected by elimination. They start with the first person, and both sides have a chance to eliminate that person, if no one does, then that person serves on the jury. I was the 7th person for a 6 person jury.

    So Close! Maybe next time.

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  5. My mare Maisie might be a sooty - her dark areas are top down and she does have some cobwebbing as well as dappling. Is dappling a gene or a variable phenotype?

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  6. Honestly, I'm not sure what dappling is! I know some colors have it, like champagnes often have reverse dappling, bays dapple when healthy, buckskins dapple when sooty. No idea of the genetics behind it though.

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  7. Pangare is a new one to me!
    For a long time I assumed that if you rode western, a red horse was a "sorrel," but if you rode English, the same horse was a "chestnut"!
    I remember the prettiest sooty palomino, with a pure white mane and tail, from when I was a kid--his name was "Tic Tock" and he was the first English/western versatility horse I had even seen. And he cleaned up at all our local shows.
    Perhaps I can help a little with the pinto patterns, starting with the fact that OLWS is not the pattern, but the result of homozygosity (is that a word?) of the "frame" overo gene. And there's one other overo expression besides frame and sabino, "splash white," which actually looks like the horse has been "dipped" feet first in white paint. Looking forward to it.
    I stop with that much, and give you a chance to talk about the patterns.

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  8. Fascinating facts and info on coloring and genes. It's always confused me, especially since folks just keep breeding so many different mixes of colors to try and get something unique and different.
    I've never been called for jury duty. Isn't that weird?

    Looking forward to your pinto patterns, since I've got a pinto of my own :)

    ~Lisa

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  9. Evensong, I might take you up on the pinto pattern help! My terminology on frame is... not well used! None of my horses have frame (what many people with out pinto colored horses call overo) and I'm a bit weak on amount of white patterning on tobiano. I have the bare bones basics. Needless to say, I've been brushing up in the last few days.

    Now, sabinos, splash, appaloosa and appaloosa pattern genes... oh yeah, I can make even a dork's eyes glaze over with my unending amount of useless (well useful for ME) information.

    Lisa, it's confusing when you try to look at it all at once. If you think about it more like building blocks, with each gene adding to what comes before it, then it's a bit easier. I always thought of genetics kinda like cleaning my room as a child: with all that mess, I never knew where to start! Once I took things one step at a time, everything started to fall into place.

    Of course, I have to mention here that my favorite horse color is E? A? (red bay). I like the basics. Add a thin blaze and a white sock, and I'm in love!

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  10. What?! Where's the pic of our very favorite little sooty Palomino?

    Is the dark coloring on Poco's shoulders sootiness or is that just part of being bay?

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  11. I like the way you grouped your color related posts!

    Sorry about the jury duty, or lack of. It's very interesting, and one feels like they are making a little difference. I always like it when I have gotten chosen, but it's hit or miss. There is always one side that wants you, and one that doesn't - for much the same reason. Hope you make it to the final cut next time.

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  12. Thanks for the compliment Aurora! I keep trying to get picked for jury duty, and everyone thinks I'm crazy for actually wanting to do it.

    And Leah, Quaker doesn't show sooty as clearly, and in pictures he looks rather...plain ol' palomino, so I used a more drastic example. Sorry.... your boy was skipped over for a prettier model! =p

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  13. I like the way you grouped your color related posts!

    Sorry about the jury duty, or lack of. It's very interesting, and one feels like they are making a little difference. I always like it when I have gotten chosen, but it's hit or miss. There is always one side that wants you, and one that doesn't - for much the same reason. Hope you make it to the final cut next time.

    ReplyDelete
  14. Fascinating facts and info on coloring and genes. It's always confused me, especially since folks just keep breeding so many different mixes of colors to try and get something unique and different.
    I've never been called for jury duty. Isn't that weird?

    Looking forward to your pinto patterns, since I've got a pinto of my own :)

    ~Lisa

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  15. :-)
    I love learning new things.
    So, am I correct in saying my haffies are pangare...or do I say they have the pangare coloring or pangare modifier?

    ReplyDelete