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Silver Dapple Eye Issues

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Jill

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Before people here have talked about a genetic eye problem that is seen only in horses who carry silver dapple. I hadn't paid a lot of attention to it in the past so don't remember much. Can people who know what I'm talking about ("Silver Dapple Eye Anamoly" maybe?) give me information or tell me where to find information? I didn't find it in any of my mini books, but maybe I don't know the right term for it!

Thanks a lot!
 
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kaykay

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hi jill

here is a website with info on it www.ramseywm.tripod.com/sdl/

its called ADS or anterior segment dysgenesis

Keep in mind this is seen in HEAVILY bred silver dapple. Like generation after generation of silver. This is why its rampant in Rocky Mountain horses. But i have to say i have now seen 3 minis with this condition in the last year. If you have never heard of it or dont know about it chances are you wont pick up on it

When you see a horse with this they look like they have insect eyes. And the weird thing is if you look at an angle you can see right thru the eye like looking thru glass
 

Dona

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Lisa-Ruff N Tuff Minis

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another thing to keep in mind is that with so many people calling silver bays chestnuts or palominos or even duns sometimes you dont realize what youhave is a silver based horse and might not look for the eye issue. I have had one foal with it.
 

Hosscrazy

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Very interesting - I had no idea! I'm on my third generation of silver dapple (Just bloodlines) and have not run into this problem.
 

CKC

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One of my fillies- "aunts" appears to have this as well as my silver bay gelding. The eyes stick pretty far out you can't miss it. I feel bad because he has an eye injury before I bought him where he punctured it. Now I'm wondering if it was because he has trouble seeing.
 

wpsellwood

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So this is the same thing that some people refer to as bubble eyes??? Ive seen a few of them and they were National champs. Interesting
 
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Lisa-Ruff N Tuff Minis

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for me wiht our baby that had it more then his eyes being big as they werent abnormal that way it was his pupils didnt ever get small they were always big and stuck that way some i have heard are the opposite and they dont get big
 

auledasacres

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I wanted to respond. We bought a horse last year as a show gelding. He has ASD from the silver gene. You can check him out at our website. It includes pictures of his eyes.

Our boys has fragments of pupils and can see shadows only. He has cyst on the inside of the eye and has cataracts. He will eventually go blind. He is only 4 years old.

Our website is www.auledasacres.com. We decided to put a page about him to educate others on this condition so someone else would buy a horse like this without knowing the truth.

Hope this helps.

Traci
 

Dontworrybeappy

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It's important to note that this genetic fault isn't *automatically* in every silver dapple horse - just that it can be passed along by silver dapple horses who have the fault.

There are plenty of perfectly normal-eyed silvers, just as there are non-melanoma greys, etc.

It is something to be aware of when breeding silvers, though. We check eyes on all our new silvers!
 

Dona

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It's also important to note that ASD manifests itself in various degrees. And, only a small percentage of horses with ASD will actually go blind. But it is definitely something to be concerned about when breeding with the Silver gene...as so many of our Miniatures carry it!
 
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kaykay

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the important thing is as breeders we all need to be aware of it and be able to identify it. The one i saw at auction was one of the worst i had ever seen and she was just a yearling. I was shocked how many people walked by her and said how cute her bug eyes were
I was also shocked how many reputable breeders that have been breeding for years didnt have any idea of what it was. It is without a doubt inherited so any horse carrying this should not be bred
 

Dona

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kaykay said:
the important thing is as breeders we all need to be aware of it and be able to identify it.  The one i saw at auction was one of the worst i had ever seen and she was just a yearling.  I was shocked how many people walked by her and said how cute her bug eyes were 
   I was also shocked how many reputable breeders that have been breeding for years didnt have any idea of what it was.  It is without a doubt inherited so any horse carrying this should not be bred
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Yes...it is inherited, but the trick is knowing what horses carry it, as MANY Silvers do "carry" this gene without showing it. So, the only way you can be absolutely sure you aren't passing it on, is to never breed two silver-carrying horses together. And, THAT is another problem.....there are still SO many Miniature breeders who don't know how to identify "Silver" carrying horses!


Here is some interesting information on ASD....

The Nature of ASD

ASD is a “semi-dominant†gene. When the horse inherits one gene only from one of its parents, there is only a very slight physical indication, while two genes will cause more differences. With one gene, you see small, harmless structures behind the lens called “cystsâ€. They have no effect on the horse or its ability to see whatsoever. This will also not change over time. Cysts can usually only be detected by an experienced veterinary ophthalmologist with special equipment. About 87% of horses that carry a single ASD gene will show “cysts.†The remaining 13% are “silent carriers,†and can pass on the gene to offspring to the same degree as horses whose genetic status is visible.

When a horse inherits two ASD genes, one from each parent, the horse will almost always show other differences in addition to the cysts. (This is the horse that in lay terms has become known as the “ASD†horse.) Many of these are easily seen if you know what to look for. Not all homozygous horses will have all of the various differences which are part of the ASD syndrome – most will exhibit only some of them.

It has now been determined by a separate study using sophisticated equipment that only one of the various ASD syndrome characteristics adversely affects the vision of the horse, and that is where the lens itself is out of proper position or is detached. This is also the only characteristic with a progressive component – the detached lens will usually develop cloudiness that worsens with time.

Of all homozygous horses, only about 10% will have the subluxated lens which affects vision – a very small percentage of the whole population. If you are buying a horse, you do want to make sure that your candidate does not have this particular characteristic. If it does not, then the horse should be perfectly fine for using purposes no matter whether it has one ASD gene, two ASD genes or none.

Color and Breeding

If you are intending to breed a horse, the ASD gene status of your horse is something you should know in order to select a mate that will minimize chances of a homozygous ASD foal, as it is only the homozygous foal that has any chance of having affected vision. Again, we believe that any "chocolate" or "red chocolate" horse will carry at least one of these genes, and until we have a DNA test for the presence of this gene, horses should be bred with this assumption, regardless of the results of a visual exam. A sorrel or chestnut horse may carry none, one or two copies of the ASD gene. If you are unable to determine the ASD gene status of your horse from its color and/or its parentage, a veterinarian trained in the techniques for detecting ASD should examine the horse.

A horse that does not carry any copy of the ASD gene, (again, we believe this includes true black and bay horses), can be bred to any other horse, even a homozygous ASD horse, without fear of producing an ASD foal. Homozygous ASD must come from both parents. The horse that does not carry a copy of the ASD gene is symbolized as "aa."

A “cyst only†horse, that is, a horse which carries only one copy of the ASD gene (symbolized as "Aa"), can produce any combination of normal "a" and ASD "A" genes in offspring, when bred to another Aa horse. The chances with each Aa-to-Aa mating are as follows:

25% normal (no ASD gene and no silver dapple gene-"aa")

50% “cysts†(a single ASD and a single silver dapple gene-"Aa")

25% homozygous ASD (two ASD and two silver dapple genes-"AA")

It is this last category only which is at risk for affected vision – 10% of the 25% will have the subluxated lens (or about a 2.5% probability altogether with this breeding.) The homozygous ASD horse is symbolized as "AA."
 
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littlearab

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This is the reason I sold Dreamer.

He is a silver dun, but most of my mares also are siver color based.

I decided it was not worth the risk of having foals with health issues.

So much cna go wrong it only made sence to remove the risk.

I found it hard to sell him becuase of his silver based color. Everyone loved him, but the silver gene was a big reason most buyer passed.
 

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