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.

Wednesday, April 20, 2011

Varnish Roan

Varnish Roan, it's a poorly understood aspect of appaloosa coloration.  We know it happens, but we have little ability to accurately predict its progression.

Appaloosa coloration is controlled by 2 things.  First the Leopard Complex gene, or LP is what we call the "on switch".  With out at least one copy of this gene the horse will appear solid - regardless of the other genes the horse carries for appaloosa color.  The second thing is a gene complex we cal "PATN" or pattern.  In other words, there are multiple genes that do almost the same thing, so get grouped together in their purpose.  Because we have not yet mapped out these genes specifically, but we know they exist because of studying inheritance (phenotype studies) we can only talk about these genes as a group.  So, when we say a horse has PATN, we mean it has at least one of a possible 30someodd genes that cause pattern.  One of the pattern genes has been shown to be independantly inherited, and that is the leopard pattern.  We call this gene PATN-1, and we know that it is a specific gene on its own, and not a combination of multiple genes working together.

Head hurt a little now?  It's ok, I'll explain that as we go!

First, we need to understand what is and what is not pattern.  Appaloosas change color over time, most of us who deal with these colors know and love this about them.  Here's one example:
This is Shadow.  The pictures show her color change from the summer of her yearling year to the early spring of her 2 year old year.  Summer coat, fall coat, and the start of her next summer coat.  She was born solid black with appaloosa characteristics only.  All of this white on her is caused by the LP gene ONLY.  Shadow has no pattern.

Now, compare that to this:
That is Rico, shown from baby to yearling.  As you can see he was born with all that white on him, and it has changed very little as he has aged.  His white area - called "dense white patterning" - is caused by a pattern gene.  This difference is very important in understanding varnish roan, and how and why it does what it does.

Varnish Roan is caused by the LP gene ONLY.  This effect is what classifies LP as a "pattern" gene (like tobiano, roan, frame, splash, etc) and not just a color gene.  The LP gene has a few specific functions: it coagulates pigment, and that can be seen in the striped hooves, mottled skin, and it also causes white sclera (human eyes) in LP carrying horses.  Most of those traits are a simple result of the pigment coagulation thing it does.  If you clump the pigment in the hoof, then it will grow out in stripes, in the skin the clumps result in pink areas of skin showing through, and in the hair it causes white areas to be unpigmented and pigment to fade as the horse ages.  Only the white sclera is not a direct effect of coagulation.  In actuality, that white sclera is a sign of the gene's main function (formation of eye cells).

Now, Varnishing comes in MANY forms.  While only the style of roaning that leaves bars on the face and bony areas is thought of as varnish roan, all LP roaning is the same thing.  Here are some different examples of roaning in LP colored horses:

This is your common "varnish" type of roaning.  Note the heavy dark areas on the face.















This mare showed snowflaking (RIP Trouble).  She gained more of those large white areas every season.  This is another form of roaning, with a different name, but genetically it's pretty much the same thing as the above.














And this mare is actually the oldest of the bunch, but has the least roaning.  All of those little white dots technically count as "snowflakes" but you can see that they are a very different style of roaning from the other 2.  Again, genetically, it's all the same thing.





And this mare shows what is called "frosty roan".  This type of roaning is actually what allowed the appaloosa colored quarter horses to "appear from nowhere".  For so long, these types of minimal roans were assumed to be related to classic roan, and not appaloosa roaning. Take this style of a roan, and breed it to a solid horse carrying a pattern gene and suddenly you get Bright Eyes Brother, or Remnic in Spots (isn't that his name?).... an appaloosa colored AQHA lined horse.


Now, the question most people have, is "how do I know what my horse is going to do?"  Well, sadly, you really don't know.  Oh I can tell you that a horse showing characteristics WILL roan, but I can't tell you what style, nor how drastically.  ALL appaloosa colored horses roan.  If you check out Rico (the bay blanket colt above) you can see that he does have some roaning progression, but not much at all.  It has nothing to do with his pattern though, but rather the same reason why the black mare has so little and such small snowflakes.

It's all about suppression and enhancement.

Chestnuts always roan more then bays.  Bays more then blacks.  High white horses more then those with no face and leg markings.  Now these things we can see (the base colors and markings) but there are other genes that we can't see.  One example is in my draft crosses.  The same gene that allows a Clydesdale to have high white with minimal roaning and sharp edges also affects Rico's lack of roaning progression.  What is it?  No idea!  But with his high white, he should be roaning more then he is.  His full brother Scorch is still almost solid black as a 4 year old, yes has high white markings.
As you can see, Scorch has a blaze and a left hind sock.  Compare that to Shadow who was born solid black (above).  Shadow should have roaned less because of less enhancer genes (white face and leg markings are enhancers) but instead she went over board with her roaning.  Scorch though, who should have significant roaning, instead has almost none.  The answer to why lies in genes we do not yet know exist.  We know their effects, but not what they are, nor what their main job is.

Now, keep in mind that most color genes (maybe all) actually do something more important first.  The appaloosa gene controls eye cell formation.  This is why homozygous appaloosas are night blind.  Frame controls the nerve production of the gut, hence the homozygous form of lethal white results in malformed intestines that fail to function and lead to death.  Most of our "unique" colors are in reality a mutation of a "normal" or wild type gene.  Now some of those alterations are so minor as to only cause color changes in the hair, such as creme.

But Varnish Roan is just an effect of the LP gene.  Why do the bony areas stay dark more then the fleshy areas?  Notice on Katy (above) that her cannons, hip, shoulder, and face are still mostly dark.  This has to do with temperature and its effect on pigment production.  The warmer it is, the better the pigment can spread and show up.

Now, here I'm going to postulate a theory of my own.  There is NO science to back this up...yet.  I am doing some studies in my own herd though, but it's a long process, and I'm probably too lazy to ever bother publishing it.  But, living in Texas, I often has severe winters, and other times I have super mild winters.  Scorch was born after a very mild winter.  Warm temps all winter long with almost no freezing at all.  He also "cooked" for 364 days!  All that nice warm time for him in utero resulted in a horse with minimal white pattern showing up.  On the flip side, his full brother Rico was born after a disgustingly cold winter.  Rico also inherited more pattern genes, but they showed to "full strength" in him.  His siblings with the same pattern (all inherited from the same sire who carries 3 obvious pattern levels) had less "wow" in their pattern, but were born after warmer winters.

Compare these foals:


All carry the same "pattern" although 2 of them are homozygous (The black filly Nox, and the seal bay colt Zire).  Now, in theory, Rico should roan more then the other 2 because he's bay, with sabino, but in reality.....
And that's just after the shedding of their foal coats.  Zire and Nox roaned as expected, with Zire roaning more, but Rico was born a year later (all pictures of babies at same age) and had a severe winter while in utero.  Hmm.


It's my theory then, that while in utero, if the cold temperatures alter the foal's environment by even a fraction of a degree, this might be allowing the base color pigment to flow more across the embryo.  If that's the case, then it might be possible that the increased coverage by pigment is something that stays with them for life, thus making those minimal snowflakes and frosty roans.  For appaloosa color breeders, this is probably not good news, as we do not want to freeze our horses in order to get loud colors!  I only have 4 years in on this study, with a handful of horses to compare to.  (Full disclosure:) To get better and more solid scientific facts I will need many more years, so for now, it's nothing more then my personal theory and take it for what you paid for it. 

So basically, Varnish Roan is nothing more then an effect of the LP or "on switch" of appaloosa color.  The type and amount of changes overtime are not yet understood well enough to be predicted or bred for.  With the current leaps in understanding of LP color, we all hope that this will be one of the next things they study.  Personally, I love a striking varnish horse.  That stallion (first picture) and his face bars is lovely to me, while others find it ugly and distasteful.  But that's the beauty of horses!  We all have things we like, and it doesn't have to be the same.

As more science comes out about it, you can believe that I will be talking about it here.  So lets give the Appaloosa Project a hand.  I believe they are still offering color testing at the U of KY as a fund raiser for these studies.  Get your horse's color genes tested, AND help support the science that will be creating the DNA tests for all of our crazy appaloosa pattern genes.

16 comments:

  1. Fascinating stuff, as usual!

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  2. I'm a bit dizzy with info here, but really very interesting stuff. Thanks!

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  3. How can anybody think Spot is ugly??? Crazy talk.

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  4. Thanks Pinz!!

    Your genetics and breeding posts are SO informative and yet easy to read. :)
    What you said about the possibility of temperature affecting the outcome of colour reminds me - when we got our sealpoint Siamese as a kitten I was told that if I wanted her points to get dark to try to keep her in a colder part of the house for the first few months. Hmmm....

    Incidentally this is why I wanted info on Varnish Roan (look at the second pic):
    http://myhorsesmylife.blogspot.com/2009/01/wordless-wednesday_14.html

    That's our Appy Raincloud, (aka Applejack, Applejackass lol) We've had him a few years and notice he's still getting lighter in certain areas (ie neck, shoulder, barrel) His registration papers say bay with white blanket (not sure of his breeding, he was bought as a husband safe horse) ;)

    Do you happen to know if that study is open to Canadian Appys? Or how to get in touch with them?

    Thanks again :)

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  5. PS - how did the dentist go? Seriously if you're have to get a root canal they are NOT that scary!

    Oh and I re-read my comment, that part about the Siamese kitten should read if we wanted her points to get darker.
    Also we do have the papers for Raincloud, they are packed away though so I don't have them on hand.

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  6. Cdn, the dentist went well... gonna be posting a new picture of my face and a whole update on it =)

    And yes, the study is open to Canadian appaloosas, infact, it has Canadian scientists involved too. Shiela Archer is Canadian and does much of the teaching. Check out http://theappaloosaproject.info

    I know there's an online classroom, which has a small subscription fee ($35 bucks or so). That fee is used to help pay for all the research as well (since DNA hunting supplies aren't cheap!). The scientists there will actually answer your questions and have past questions available for you to look though... and there's a TON of information there! Basically, if you want to know the science behind LP colors, it's the place to research it all.

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  7. I don't understand the whole genetics stuff, but do find it interesting. Most of all I just enjoy seeing all the great photos of gorgeous spotted horses here :)

    Hope you're feeling better?

    Happy Easter.
    ~Lisa

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  8. Cdn, the dentist went well... gonna be posting a new picture of my face and a whole update on it =)

    And yes, the study is open to Canadian appaloosas, infact, it has Canadian scientists involved too. Shiela Archer is Canadian and does much of the teaching. Check out http://theappaloosaproject.info

    I know there's an online classroom, which has a small subscription fee ($35 bucks or so). That fee is used to help pay for all the research as well (since DNA hunting supplies aren't cheap!). The scientists there will actually answer your questions and have past questions available for you to look though... and there's a TON of information there! Basically, if you want to know the science behind LP colors, it's the place to research it all.

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  9. PS - how did the dentist go? Seriously if you're have to get a root canal they are NOT that scary!

    Oh and I re-read my comment, that part about the Siamese kitten should read if we wanted her points to get darker.
    Also we do have the papers for Raincloud, they are packed away though so I don't have them on hand.

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  10. I'm a bit dizzy with info here, but really very interesting stuff. Thanks!

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  11. It would be interesting to have a Canadian or far northern Appaloosa breeder keep similar records on color and temperature. It would be handy to know if keeping the mare in the barn effects the foal color, since it would impact the temp of the mare. You have raised some amazing questions and ideas. 

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  12. Mammalian SpecialistSeptember 16, 2012 at 12:09 PM

    I'd like you to read up on some modern Genetics with horse color patterns. It actually answers all of your "we don't know yet!" parts.

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  13. Have any links for it?  I just did a quick search, and haven't found anything definitive yet, but would love to see if some new progress has been made.  Sadly, life has stepped in, and I haven't had a chance to get into my genetics passion since i wrote this well over a year ago.  Once a few things slow down, I hope to be able to come back and update all of these old posts on genetics, but if you have links to credible sources, I'd be more than happy to squeeze it in sooner.

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  14. I have a friend with a Gypsy Cob that appears to be a strawberry roan and white.  Genetically, she is a black and white horse however.  No red gene, no sabino no agouti.  However she does have 1 appy gene.  She is, visually, a strawberry roan and white.  No black. I'm thinking she might be a "varnish appy", but I'm curious if the appy gene would modify the black to appear red in this case?   any ideas?

    thank you!

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  15. Wow! Had to do a triple take on your picture of Trouble. She could be a TWIN for my mare, Tater!!! Same coloring, pattern distribution, sock, conformation and bulky size...everything! Sure have enjoyed the genetics info. Color/pattern genetics has always fascinated me but it's a confusing world. Thanks for the straight forward explanations. Got an interesting twist for you, though. Can you address the genetic possibilities in Pintaloosa breeding (App x Paint/Pinto)...specifically bay varnish roan and chestnut frame overo. Thanks!

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