Equine Dwarfism 101, version 2 (Updated 2014)

Discussion in 'Horse Colors / Genetics' started by Threnody, Mar 22, 2014.

  1. Tremor

    Tremor Senior Member

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    Well, to be honest we had based our knowledge on the previous research of John's.... Which was from the late 90's. It was extremely out of date, and obviously it won't apply anymore since we know that dwarves can be more than one type combination.

    I think it will be more interstesting when the rest of the research on SA dwarfism comes out, along with the testing.
     
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  2. Threnody

    Threnody Senior Member

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    I know that part of the reason Achondroplasia isn't used anymore for the SA dwarfs is because the mutation isn't in the same area as Achondroplasic dwarfism is in other animals and even humans. It was called Achondroplasia initially since it was visually similar in it's expression by causing shortened limbs.

    It's a similar story with the other old names. They were parts of the condition that were descriptions of how it expressed and not names for the condition as a whole. For ACAN dwarfs there are multiple genes on the same locus, so having 3 names for all the mutations depending on how they look doesn't work since there is a lot of expression crossover. PLUS the mutations can express in compound form (D2/D4 D1/D3 ect.) Some are more severe than others, and some are aborted, but they are all caused on the same locus. So a collective term of chondroplasia-like is more encompassing.

    Then we also have Skeletal Atavism in minis(formerly Achondroplasia) and in friesians we have Osteochondrodysplasia (A sister term for Achondroplasia which describes having defective cartilage). These forms may show to be the same form of dwarfism. The difference in the name is the fact that different research is happening on both. In color genetics a similar situation has happened. The Pearl dilution was called Pearl by a European research group while it was called Barlink/Apricot by an American research group who (unbeknownst to them) were both looking into the same gene at the same time. It was later found out that Pearl and Barlink were the same color mutation. Since the Pearl group published first they got to name it. So we may see the SA/Osteochondrodysplasia form of dwarfism being consolidated as well. By then it may even have a new name that acts as a better description for it depending on what they find.

    As new knowledge is gained renaming things can become necessary. Though it can cause confusion. I know a few years ago I had a hard time finding recent information on ASD (Anterior Segment Dysgenesis) in the eyes of Silver horses. I then found out from someone else that it had been renamed MCOA (Multiple Congenital Ocular Anomalies) and found so much more current updated research on it. After reading the papers the name change made clearer sense. Silver causes various forms of eye problems, not just one as the first name suggested.

    So as far as dwarfism research is concerned. Brace yourselves. New long scientific words to memorize may be coming. :)
     
    Last edited: Aug 18, 2014
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  3. Threnody

    Threnody Senior Member

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    If you're willing to test him it would be very interesting to see what he is! He's similar to the situation with some of Tremor's horses. Is it dwarfism or just conformational issues in a smaller than normal package? We have no idea what the full expression range of ACAN dwarfism is yet, or how minimal it can express. Plus most people on the facebook group are only posting their horses who test negative, or their carriers who aren't used for breeding. So we aren't getting as many examples of tested and proven ACAN dwarfs to gain a better visual picture of the expression continuum.

    On another note, he looks like he might also be a slipped Tobiano. I'd want to see if he tests for that too! XD
     
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  4. thegatorgal

    thegatorgal Registered

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    Here is a pic of the other dwarf at the Animal Sanctuary I work at. I meant to put these up a couple months ago... but better late than never :D

    Her name is Mouse, and she came from a mini breeder with no scruples trying to sell her for $3000 :no: Anyways, she is in a lot better shape now and her hooves are really starting to come around. She has one that always wants to roll under due to her front leg conformation, but our awesome farrier has her looking way better.

    Despite all of her physical deformities, she is very healthy and sassy! She rules her paddock of fellow mini misfits including a blind donkey. She is missing her right eye and her ears are crinkled, though she can hear. She has appy characteristics and slowly gains more mottling around her muzzle every year.

    [​IMG]
     
  5. Tremor

    Tremor Senior Member

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    I can't help but wonder which breeder she's from and what her blood line is. If you know, would you mind messaging me? Insanely curious, especially with the appaloosa.
     
  6. thegatorgal

    thegatorgal Registered

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    The owner of the sanctuary isn't around much this time of year, but next time I see her I would be glad to ask :)
     
  7. prairiesongks

    prairiesongks Senior Member

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    Do you remember Munchkin, our 31 inch gelding, who may be a ACAN dwarf and is a conformational wreck? I posted pictures in the other thread. We considered getting him tested, but for the price, felt it would be better to put that money in the emergency horse fund to help cover any issues he may develop. He's a gelding with an unknown pedigree so won't be passing on his genetics.

    [​IMG]


    I think Firegurl's Chase may have the same issues as our Munchkin.
     
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  8. firegurl979

    firegurl979 Senior Member

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    omg its a black Chase! lol
     
  9. Trubandloki

    Trubandloki Senior Member

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    Very interesting read. Thank you OP for making it so easy to learn.
     
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  10. prairiesongks

    prairiesongks Senior Member

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    I immediately looked out the window to check on our mini's when I saw Chase......they seem have to come out of the same mold, but a different artist colored them!

    .....and that's even down to the snarky face!

    [​IMG]
     
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