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, July 21, 2010

The basics of white patterns

The first thing you need to know about patterns is how they happen.  For various reasons (depending upon the genetics) horses have areas with out pigment.  This can be anything from face and leg markings to solid white horses.

My father used to always ask me jokingly, "Are Zebras white with black stripes, or black with white stripes".  Once I got into genetics, I was able to answer that question.  Zebras are black with white stripes like this picture shows.

The reason is that white markings are actually areas where the pigment production is inhibited.  This means that those cells still have the code for the horse's (or equid's) base color, but something prevents the color from being produced.  That "something" could be many different things, from specific genes to outside factors.  If you keep in mind that a foal starts as a single cell, and as it develops that cell divides, and then those cells divide, you can see how early cells will end up far from other early cells, but later cells will be close to each other.  When the embryo is only 2 cells, one might end up at the tip of the nose, while the other will be the tip of the tail, but in a near term foal a new tail cell will be next to a new tail cell.

Genetic decisions (which genes are activated) are altered through out embryonic development.  Cells are "triggered" to be skin cells, or heat cells, hair cells or hoof cells, depending upon many super technical bio-mechanical things.  Never fear, I won't dork out on those, but it does help to have a basic grasp of this phenominon to see why patterns vary so widely!  Specific triggers can cause genes to be activated, and changes in the body to occur.  An example of this is how a newborn takes it's first breath, but before that the baby gets oxygen through the umbilicus.

First of course, the DNA coding is the "blue print" of what will happen, but just like in construction, things don't always go as planned.  Things such as temperature, position (is the foal pressed against the uterine wall) gestational time, nutriton, and a myriad of other factors all have their role.  A good analogy for this is such construction problems as: expansion of materials in heat, misreading the blue print (yes, this happens in DNA too), and poor building supplies.

Here is an example of some face markings from clones of Smart Little Lena.  These horses have exactly the same DNA, but the difference in markings is due to "external" factors like I mentioned above.  No, we don't always know what did what, but examples like this allow us to take steps to figure it out.
You can see that all of the clones have a similar "feel" to the shape of their blazes, but some have more, and others less white.  The third foal's blaze curves to the opposite side as the donor's (original horse's) blaze!

There isn't a more perfect example of the difference between nature and nurture then clones.  Nature includes DNA, while nurture includes just about everything else.  Each of these foals had a different surrogate dam.  Differences in the mare's average body temperature, location of the foal in utero (right horn, left horn, lots of room or cramped in there) all can change things even though the DNA is the same in each one.

Head hurt yet?  Yeah, it gets worse.

Now, pattern genes basically code for pigment to NOT be produced.  Because of the way the foal's cells develop while it's a fetus, this results in pigment cells being next to similar pigment cells.  Think of a paint horse.  Big blobs of color and white are caused because of this.  Also, the path of cellular development can cause patterns to appear.  You can often see the cellular pattern in leopard appaloosa colored horses like this guy:
For everyone drooling right now, that's Mystic Warrior, a rather popular 3/4 Friesian foal who caused quite a stir and then people lost interest when they learned that he's grey.  His spots show just how the cellular motion during development happens, from the spine down, and across the body.  You can almost feel that his spots are "running" like wet paint.

All horse markins will be affected by that.  This is why you don't see sideways blazes, or appaloosas with only a spotted area on their heads.  It's all about what cells are first and which are last.  In explaining patterns over the next few days, I will refer to this migration of cells, and how some things depend upon external factors to get more "bang for the buck".  Appaloosa is one of them.

Also, just a bit of trivia for you:  This pattern of migration is also why sooty tends to be top down, pangare tends to look like it comes from the bottom um, and why agouti pushes the pigment to the points.  For me, learning about cellular migration was one of those things that made everything else fall into place.

Again, if I've lost you some where and you feel like your head is about to explode, please feel free to email me.  I will explain things in different ways, I'll try over and over.  I know many people are very interested in horse colors, but genetics don't come easy to them.  If you want to know, but don't want to feel selfconscious, simple send an email to me at:  heather@ironridgesporthorses.com

Today, I only have an opinion question.  While digging up the clone pictures, I saw many discussions based around breeding to a clone.  Some people commented that because a clone might not have the same performance ability, they wouldn't think about it.  Others would if only their registry would allow it.  So, would you, or would you not ever breed to a clone (assuming you were wanting to breed a horse)?  Why?

20 comments:

  1. This comment has been removed by the author.

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  2. Correct me if I'm wrong, but the whole cloning idea to me seems silly. Even if, genetically, the horse is the exact same, that doesn't make him the same horse. There's so many factors that make a horse who he is, not just his DNA. So no, breeding to a clone seems wrong. Just because you clone Secretariet, it DOES NOT make that horse Secretariet. Period. (figuratively speaking of course)

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  3. I don't breed, so I can't help on the clone question.

    Fascinating post - I've always thought it might have something to do with cell migration seeing that a lot of common white markings end up on the head and legs, but I didn't get the connection to whole-body patterns or other coat modifiers. (My genetics knowledge is antique and rather skimpy.)

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  4. The cloning question is a good one. I'd like to think any horse could be good at any event, but it's obvious that Arabs are better suited to endurance, Quarter Horses for cow work, and warmbloods for dressage. And the upper echelons of various sports are filled with certain successful bloodlines, so it would seem that a clone of Smart Little Lena would have the propensity to be very good at reining--but then that whole nurture thing comes in, you know, nutrition, conditioning, training. And the cloning process AIN'T cheap! So it will only be the successful, RICH folks, who can afford the cloning AND the raising/training/campaigning of the resulting foal (a high risk process, in itself) that will even go that route. As for breeding TO a clone, I suppose if it was registerable, there would be some argument for at least starting with the "great" DNA. But I suppose if something as simple as color can vary from clone to clone, more complex factors such as intelligence (trainability) and physical capabilities could also vary somewhat...

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  5. By the way, the whole cellular migration concept is new to me, but obviously explains one of the primary differences between Tobiano and Overo (which is confusing to most non-pinto folks)--the fact that white does not cross the back of an Overo and almost always does on a Toby. Trouble is, before all this genetics stuff came along, there wasn't much understanding of what created which patterns. Tobiano was the easiest described and replicated, as it is, I believe, a single dominant gene that determines that pattern. But Overo has the three (or possibly more, there are probably at least two if not three different genes involved in Sabino) separate patterns, that have been intermixed for a long time, just from not knowing.

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  6. My opinion on breeding to a clone is that it would depend. If the original was not available for breeding, (and I wanted a foal from him/her) then yeah.

    Like Gem Twist, an AMAZING jumper, who was gelded young. Scamper, also a gelding. Both have been cloned and their clone is to remain intact. For me, it doesn't matter if the clone is as successful as the donor, because a foal would not inherit the donor's training or history.

    I would like the clone show some aptitude though. Maybe not as much heart, and I definitely would not expect the same level of success as the donor. But when you breed to a horse all you get is the DNA. The clone's DNA is identical to the donor horse, so, it's a good indicator of what inheritable potential a breeder could expect.

    I mean, if they cloned Big Ben.....mmmmmm, I want one!

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  7. And thanks Evensong for the pinto stuff. I think I'm pretty up to date on it then. If you'd do me a favor and watch my terminology for me?

    I tend to call frame "overo" and then use the proper name for sabino and splash. I should be referring to the overo patterns, and calling them splash, sabino, and frame. I also find myself throwing out OLWS as a term for the genetics, not the homozygous state.

    Thanks!

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  8. I would have no problem breeding to a clone if the horse met my needs. Having a very good grasp of scientific concepts, I know that a clone is just a twin born at a different time and from a surrogate mare. (My brutha frum anutha mutha, LOL!) There is really nothing wrong with clones themselves and if they make it to a live birth are usually genetically sound and have all the same advantages or disadvantages of any other foal.

    I wish someone would clone O about 5 times so we could see how leopard migrates and what effect temperature would have, with several surrogates in Canada and several surrogates in Florida. He's got a hidden leopard pattern; if it had been warmer when he was cooking, would he have been 100% leopard? Hummmmm,.... If I had a miiiiillllion dollars to toss at it I would; I'm that curious, LOL! (And he's that fabulous!)

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  9. Cheri' i must say your horse is beautiful!! Lol.

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  10. Cheri' i must say your horse is beautiful!! Lol.

    ReplyDelete
  11. And thanks Evensong for the pinto stuff. I think I'm pretty up to date on it then. If you'd do me a favor and watch my terminology for me?

    I tend to call frame "overo" and then use the proper name for sabino and splash. I should be referring to the overo patterns, and calling them splash, sabino, and frame. I also find myself throwing out OLWS as a term for the genetics, not the homozygous state.

    Thanks!

    ReplyDelete
  12. I don't breed, so I can't help on the clone question.

    Fascinating post - I've always thought it might have something to do with cell migration seeing that a lot of common white markings end up on the head and legs, but I didn't get the connection to whole-body patterns or other coat modifiers. (My genetics knowledge is antique and rather skimpy.)

    ReplyDelete
  13. Correct me if I'm wrong, but the whole cloning idea to me seems silly. Even if, genetically, the horse is the exact same, that doesn't make him the same horse. There's so many factors that make a horse who he is, not just his DNA. So no, breeding to a clone seems wrong. Just because you clone Secretariet, it DOES NOT make that horse Secretariet. Period. (figuratively speaking of course)

    ReplyDelete
  14. There are so many good horses out there.  I do not believe in cloning horses (how boring would that be) or in breeding to a clone.  I really don't understand what the interest is in that.  Why not try to stay away from "inbreeding" and all the genetic diseases and just stick to good breeding?

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  15. That is one beautiful foal!

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  16. Interesting comment on zebra genetics being white stripes on a black horse.  That may not be true. I have seen two "zorse" ( zebra horse crosses) and they are red duns with a stripe along the back and zebra markings on their upper legs. Exactly like my red dun QH mare. They arose from a cross between wild zebra and English thoroughbreds running together on a farm in South Africa.

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