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Ineritable "Brindle" Discovered

Discussion in 'Horse Colors / Genetics' started by Threnody, Apr 4, 2014.

  1. Threnody

    Threnody Senior Member

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    http://equinetapestry.com/2014/04/a-heritable-form-of-brindle-discovered-in-horses/
    http://www.plosone.org/article/info:doi/10.1371/journal.pone.0081625#pone-0081625-g002

    A friend directed me to the latest update of the Equine Tapestry blog written by Lesli Kathman. The second link is the open access (yay no pay-wall!) paper from PLOS ONE.

    For you color enthusiasts, as amazing as this discovery is. Do not get too excited until you read up on it.

    It appears that there is a gene that causes "hair texture" brindle. It is a sex-linked dominant homozygous lethal. It only expresses in females if they have one copy, but it is lethal in males (die in utero) and also lethal in homozygous females. Given the health issues associated with this discovery, it is not a gene that should be bred for in my honest opinion. The lines are caused by stripes of hair having sever skin issues, warts, lesions. They also have eye, hoof, and teeth problems associated with the mutation.

    On a personal note, I have images of a foal and a few other horses whom I now suspect had this disorder. The images were presented to me by their respective owners, but I do not have permission to post them. One owner posted on another forum asking if allergies could cause a brindle appearance, so now I am suspecting that their mare had this form. The dam of the mare also supposedly had the same "allergies". The fact that they were both female are an important clue to this possibility.

    This is likely the same sort of mutation that Brenda Batty Atty the famous brindle mare had. However, most of her descendants today do not have this disorder, as it appears to have been bred out of their lines. The curly gene is what the vast majority of her claimed 'brindle' decedents have today. The other horses whom I've seen with what is likely this disorder are from American gaited lines like Brenda Batty Atty herself was suspected of. This disorder could also spontaneously mutate in other breeds.

    This is starting to put a lot of puzzle pieces together for me personally, so I apologize if I am rambling.
     
    Last edited: Apr 5, 2014
  2. lucky_pine

    lucky_pine Senior Member

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    There will be people out there who breed for this, either not knowing or caring about the consequences. That scares me. Thank you for posting this!
     
  3. Threnody

    Threnody Senior Member

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    It is a sad fact that I sadly must agree with. ^

    Strange thing I'm figuring now is that this disorder would explain Brenda's Millennium. http://www.brindlehorses.com/battyatty/webped/millie.htm

    I never had a logical explanation for her color since I didn't think Brenda's brindle could produce a phenotype like this. I also didn't believe it was inheritable, until I found other families of 'hair texture' brindles (that weren't curly) two years ago. 'Millie' has white hairs interspersed with her base coat. This disorder would explain why. In her foal coat picture, you can see the different hair stripes like how foals with the disorder are described in the research paper. However she doesn't have the white markings as a foal. If she got the skin issues and lesions, her pigment production in those hairs could be damaged to the point of no longer producing color. Similar to how horses with fungal infections can get white blotches.

    The difference with fungal infection horses is that they get over their issue. These horses are born with this problem for life.

    Also. This stallion cannot carry brindle as claimed since he is male. If he did have the gene, he would not be alive. http://www.brindlehorses.com/battyatty/webped/punky.htm
    He supposedly produced brindle foals out of non-brindle mares. But all the mares he has been bred to are from lines with this disorder. The mares passed on the hair disorder, not him.
     
    Last edited: Apr 5, 2014
    5 people like this.
  4. JetdecksComet

    JetdecksComet Senior Member

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    Yep. If you look at the websites for breeding these brindle horses, you'll notice they don't mention the stripes of hair having severe skin issues, warts, and lesions or that the horses also have eye, hoof, and teeth problems associated with this mutation. Yet they keep breeding for this "color pattern" and some of the foals, while not otherwise notable are for sale for 7-9k each. :eek2:
     
  5. Threnody

    Threnody Senior Member

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    To play devil's advocate, I know for some people they likely did not know these issues connected to it. Especially if they had one animal with initially mild expression of it and decided to breed them to see if it was inheritable for the sake of science. Some of these animals do not appear to be as heavily scared with hairless patches as the horse in the study, and they may get worse over time. Hence the mistake of some owners believing it was allergies.

    Now that this information is out, I really hope this is taken into account by people who own animals with this disorder. It shouldn't be a witch hunt if they honestly had no idea. Breeders who bred en masse for this disorder over years and years seeing the linked affects, I honestly may still question a little. But people with one or two who wanted to test if it was inheritable I can't blame. This is very new information.

    I honestly hope that owners of animals with the disorder are not afraid to share their stories of these animals so we can get a better idea of how they are affected.
     
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  6. JetdecksComet

    JetdecksComet Senior Member

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    I can agree with that, but if you have a horse with "eye, hoof, and teeth problems" you probably should not be breeding it, no matter how rare the color. It doesn't matter if you know whether or not the issues were connected to the color, the fact remains that you are breeding inferior stock purely for color. That is what smacks of "Krazy Kolor Breeding" and that is what I would take issue with.
     
  7. Garfield70

    Garfield70 Senior Member

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    But brindle is inheritable and perfectly healthy in other animals, like cattle or dogs. And arent there male horses with expressed brindle that are healthy?
     
  8. RiddleMeThis

    RiddleMeThis Senior Member

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    And before we start crucifying Brenda Batty Attys breeders and the people who bred from her as we DON'T KNOW that her line has this form of Brindle.

    Its speculation.
     
    3 people like this.
  9. Threnody

    Threnody Senior Member

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    There are many causes of a brindle appearance in horses. But none besides this form are considered inheritable. I can't even really call this brindle as it isn't a color gene, but a skin condition with other health defects connected to it. It isn't even really a true form of brindle in horses such as the kind found in dogs.

    Here is a rundown of some likely causes of other forms of brindle.

    Chimerism: A non-inheritable brindle caused by two fraternal twins fusing as embryos in the womb. This can occur in horses that are physically male or female.

    This is Dunbar's Gold. He is physically male, but has 1 male set of DNA, and 1 female set of DNA.
    [​IMG]

    Dunbar was bred to Sharp One who is also a chimera. Their test breeding resulted in normal foals and resulted in discovering Dunbar and Sharp's chimerism. She has two sets of female DNA.
    [​IMG]

    It also can cause a patchy appearance. The patchy chimeras occur if the twins fuse early, while striped ones occur later. This is Litningur frá Möðrufelli.
    [​IMG]


    Skewed Roan: Sometimes roan and/or rabicano horses have their mixed white pattern not distribute properly causing stripes. Rabicano can cause a 'ribbed' stripe appearance on it's own which can mimic brindle. Extreme forms of this cause stark white stripes. This can occur in either gender and is likely environmentally caused, and therefore non-inheritable. No horses with this kind of brindle have ever produced themselves in their offspring.

    Riverdance's Marble Tigress, negative for chimerism, positive for roan.
    [​IMG]

    Rossletta, a purebred Arabian mare with skewed rabicano.
    [​IMG]

    Natal Classi, another likely skewed rabicano, as extreme rabicanos occur in his family line.
    [​IMG]

    Natal's relative Mozaik who expresses extreme rabicano that could be called brindle.
    [​IMG]

    The famous white brindle stallion Catch A Bird was the founder of a new roan pattern. His pattern was so skewed it formed white stripes. Produced offspring who appear to have roan with rabicano.
    [​IMG]
    [​IMG]


    Extreme Dun-Factor: The dun gene in horses causes concentrated pigment stripes and diluted coloration on the main body coat. The concentrated stripes form in various locations on the body. A dorsal stripe along the topline is the most notable form of dun-factor. It also causes stripes along the legs, under the belly, and shading along the neck and withers. Extreme forms of dun-factor can cause multiple locations of concentrated stripes beyond the normal areas where they occur. Although dun is inheritable, the extreme expression of stripes is not and occurs randomly. This is also able to express in either gender.

    A grullo (black dun) horse with extreme striping along their barrel.
    [​IMG]

    Binder Marks are concentrated areas of pigment on dun horses that often occur on the neck and wither area. This is sometimes also called brindle.
    [​IMG]

    Sharp Trilogy a gray grulla mare. The presence of gray likely increased her dun-factor expression since gray darkens a horses color before turning the horse lighter. This is an older image and she is likely white-gray now. Gray itself can also cause a bridle appearance.
    [​IMG]


    Gray Brindle:
    When going gray many horses get dapples. These spots have the insides gray faster than the outside causing halos and circles dappling the coat. Some horses have skewed dapples that form stripes instead of circles. It is also possible that gray chimeras may have a similar appearance while they gray, though no current gray brindles have tested positive for chimerism. Gray is inheritable. This odd graying pattern appears to occur randomly. The pattern is also temporary and will fade with age. Can occur in either gender.

    Reckless Dan a gray brindle. Has not passed on his pattern to any offspring, supporting the theory that it is non-inheritable. Older image, likely white-gray now.
    [​IMG]

    A younger gray horse showing the beginnings of a striped graying pattern instead of dapples.
    [​IMG]


    Curly: Sometimes called "seasonal brindle" these horses are not a true from of brindle in the same way that the inheritable form is not either. It does not affect coloration, but the hair texture. The seasonal part of the name is derived from their 'brindle' coat texture being most notable in the winter with their long coats. Meanwhile they shed most of their hair in the spring and summer losing the effect. Some breeders will advertise these horses as being brindle when they are in fact curly instead. The easiest way to tell them apart from the other form, is they they often have curly ear hair and often gain sparser manes and tails during the summer shed. There are two forms, one that is dominant which is common. And another that is recessive. Those who are homozygous for the dominant form of curly will often have nearly no mane or tail hair year round. Inheritable in either gender, though it isn't brindle.
    [​IMG]
    [​IMG]


    Sooty: Sometimes horses can have sooty cause primitive markings and stripes similar to dun-factor. This can also cause the occasional odd stripes along the body. I am reassessing some of my brindle files since some candidates for sooty brindle may in fact be caused by skin issues like the newly discovered disorder.
    http://www.hippo-logistics.com/dun/puzzles/sage_on_bey.htm


    Somatic Mutation and/or Skewed White Markings: I have these together since they may be related. Somatic mutation is when an area of DNA has parts of it's code altered or turned off while it's replicating in the animal. These travel from the neural crest which is located along the neck and topline of the horse. As they travel down they create stripes.Some animals appear to have similar patterns to those with somatic mutation, but they appear to have been forming white markings that were interrupted. Non inheritable and viable in either gender.
    [​IMG]
    [​IMG]

    As you can see there are many causes for a brindle appearance. And all but this most recent discovery are not inheritable. We have yet to find a healthy inheritable form of brindle in horses like the kind found in dogs and other species.
     
  10. Zuhzoo

    Zuhzoo Full Member

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    Thanks for sharing this, it's really interesting! Yep, definitely not something we should be breeding for...
    Also, great to have a list of all the causes of 'brindle' in one place, thanks again Thenody!
     
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