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  1. #1
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    Default I have a theory for the cause of cribbing

    Could hyper stretching of the esophagus result in endorphin release?

    Suppose that there is an area in the horses throat that is highly sensitive to stretching stimulation and wired directly to the pleasure centers of the horses brain.

    Suppose the act of swallowing for a horse, results in a pleasurable release of endorphins because of the stretching of the throat and esophagus that occurs.

    Then suppose that when a horse cribs, the horse is in reality hyper stretching that sensitive area of their throat.

    Then consider that the act of normal swallowing does not stretch this sensitive area of the throat as much as cribbing does.

    So in essence the cribbing horse is mechanically overstimulating it's eating-reward physiology in order to obtain an elevated levels of endorphins.

    Perhaps evolution provided the horse with an extremely powerful reward response to swallowing (eating), as a necessity for survival.

    One could speculate as to why evolution determined this necessary, but perhaps without this extremely pleasurable reward for swallowing (eating), the distraction of the horse's highly alert mind towards the dangers of being eaten by a predator, would over power the need to eat, so in response, the horse evolved this pleasure response that resulted in a stress relief system from the alertness of looking out for danger.

    When I apply this theory to the behavior of cribbers that I have personally known, it seems to explain the behavior perfectly.

    Has anyone come up with this theory yet?

    I would like to discuss ideas of how one might prove or disprove this theory.

    Any thoughts?



  2. #2
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    Interesting thoughts!



  3. #3
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    It could stimulate the vegas nerve which runs all the hell over the place and even could explain the digestion issues.

    That is not a theory on why horses crib. That is a theory on how the reward mechanism works in horses that crib.

    All horses eat. How many crib. Why?

    Why does it have to do with eating at all?



  4. #4
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    Quote Originally Posted by alterhorse View Post
    Perhaps evolution provided the horse with an extremely powerful reward response to swallowing (eating), as a necessity for survival.


    Any thoughts?
    I would argue that cribbing is not a "necessity" at all, since the horse does not have to crib to survive. I would also argue that it is in fact actually a malfunction more than likely caused by the domestication of horses. In other words confinement is the likely culprit of cribbing and would suggest you look at studies on feral equid and their cribbing habits .



  5. #5
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    Quote Originally Posted by equinelaw View Post
    It could stimulate the vegas nerve which runs all the hell over the place and even could explain the digestion issues.

    That is not a theory on why horses crib. That is a theory on how the reward mechanism works in horses that crib.

    All horses eat. How many crib. Why?

    Why does it have to do with eating at all?

    Perhaps a horse that cribs has a much greater endorphin response to swallowing then a normal horse does?

    It could be a genetically inherited trait (an evolutionary need for such a trait to exist might support this idea)?

    The horse then discovers that it can physically manipulate it's hypersensitive esophageal pleasure center by imitating the behavior it observers from another horse, or discovers by accident. This could explain why some horses seem to learn the behavior from other horses, and some do not. For only the horse with the genetic propensity will find the cribbing stimulus more pleasurable then eating.



  6. #6
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    Quote Originally Posted by alterhorse View Post
    . This could explain why some horses seem to learn the behavior from other horses, and some do not.
    But cribbing is not a learned behavior. And again, it isn't a habit of horses in their natural state.



  7. #7
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    Quote Originally Posted by alterhorse View Post
    Perhaps a horse that cribs has a much greater endorphin response to swallowing then a normal horse does?

    It could be a genetically inherited trait (an evolutionary need for such a trait to exist might support this idea)?

    The horse then discovers that it can physically manipulate it's hypersensitive esophageal pleasure center by imitating the behavior it observers from another horse, or discovers by accident. This could explain why some horses seem to learn the behavior from other horses, and some do not. For only the horse with the genetic propensity will find the cribbing stimulus more pleasurable then eating.

    There does not have to be any evolutionary reason for a trait to exist. Traits are mutations. Some are beneficial and some are useless and some are harmful. Horses that crib can be pretty happy stuck in a stall for days at a time. That would be adaptive to some situations. They never get bored! So should we make more of them? Call it a benefit and not a vice?

    So your theory is its a genetic trait and you have proposed a mechanism that would reinforce the behavior and make it more likely to continue. Thats pretty good! Nowhere did you blame stress or bad mommies or ulcers or anything anyone is doing wrong. Your theory would be a reason that horses in all kinds of environments start to crib.

    So can you think of a way to apply this theory or test it? Where are you going to focus--on the reason or the mechanism. Its a theory that helps explain why some other long necked animals crib too.

    If its hereditary, how would you fix that?



  8. #8
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    Decrease in cribbing activity in horses when opiate blockers (naloxone) is given was shown years ago. (Dodman and Shuster)
    Don't think it was esophageal stretching, though, but the behavior does trigger endorphins.

    The tendency to crib is inherited, but tends not to be expressed until the horse is stressed.
    "It's like a Russian nesting doll of train wrecks."--CaitlinandTheBay

    ...just settin' on the Group W bench.



  9. #9
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    Quote Originally Posted by hundredacres View Post
    I would argue that cribbing is not a "necessity" at all, since the horse does not have to crib to survive. I would also argue that it is in fact actually a malfunction more than likely caused by the domestication of horses. In other words confinement is the likely culprit of cribbing and would suggest you look at studies on feral equid and their cribbing habits .
    I agree that cribbing is not a necessity.

    If a horse is born with a "malfunctioning" overly sensitive esophageal reward mechanism, it might be more inclined to crib then the normal horse might be.

    Confinement could cause increased stress, and if this theory holds true, it might explain how a horse uses cribbing as a method of stress relief.

    Quote Originally Posted by hundredacres View Post
    But cribbing is not a learned behavior. And again, it isn't a habit of horses in their natural state.
    Cribbing might be a genetic trait that decreases the chances for survival for a horse living in the natural state, and therefore rarely observed in the wild.

    In essence, in the natural state. the cribbing horse would not function as well as a herd animal, and might therefor be less likely to pass on it's genes to create more cribbers.



  10. #10
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    Quote Originally Posted by alterhorse View Post
    I agree that cribbing is not a necessity.

    If a horse is born with a "malfunctioning" overly sensitive esophageal reward mechanism, it might be more inclined to crib then the normal horse might be.

    Confinement could cause increased stress, and if this theory holds true, it might explain how a horse uses cribbing as a method of stress relief.



    Cribbing might be a genetic trait that decreases the chances for survival for a horse living in the natural state, and therefore rarely observed in the wild.

    In essence, in the natural state. the cribbing horse would not function as well as a herd animal, and might therefor be less likely to pass on it's genes to create more cribbers.
    There is also less opportunity to crib. Is there any proof that confinement causes stress, that stress causes cribbing or that cribbing relieves stress? How does one objectively measure stress?

    The answers to these questions are on COTH threads from the past.

    Lets say its all true. How would we prevent cribbing in future horse populations?



  11. #11
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    Did you perhaps mean vagus nerve, the tenth cranial one?
    Although I like the vegas name better, more suggestive.
    Maybe the name is different in horse anatomy?



  12. #12
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    Quote Originally Posted by equinelaw View Post
    There does not have to be any evolutionary reason for a trait to exist. Traits are mutations. Some are beneficial and some are useless and some are harmful. Horses that crib can be pretty happy stuck in a stall for days at a time. That would be adaptive to some situations. They never get bored! So should we make more of them? Call it a benefit and not a vice?

    So your theory is its a genetic trait and you have proposed a mechanism that would reinforce the behavior and make it more likely to continue. Thats pretty good! Nowhere did you blame stress or bad mommies or ulcers or anything anyone is doing wrong. Your theory would be a reason that horses in all kinds of environments start to crib.

    So can you think of a way to apply this theory or test it? Where are you going to focus--on the reason or the mechanism. Its a theory that helps explain why some other long necked animals crib too.

    If its hereditary, how would you fix that?
    Well, first I'd want to try to understand exactly what may be happening internally in the esophagus of the cribbing horse. and compare that to normal swallowing to see what parts of the esophagus might be involved.

    Would there be any evidence of esophageal stretching caused by cribbing, more so then in normal swallowing?

    Could the equivalent of a barium swallow be done for a horse to observe what normal swallowing looks like, then compare the effect swallowing has on the esophagus, and compare that result to the effect that cribbing has on the esophagus.

    This would be my first thought, to prove there is actually something that can be focused upon, and then try to understand if it's physiologically posable for that location of a horses body to effect the horses pleasure centers.

    One might count the number of nerves in this area, and compare that number between cribbers and non cribbers.

    Or perhaps, one could do a nerve block to this area, if it's posable to do one that won't effect the horse ability to swallow, and then see if the horse stops cribbing.

    I think just proving that it's hereditary, and what the exact cause is, would have to be done before one could consider the remedy.



  13. #13
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    Quote Originally Posted by Bluey View Post
    Did you perhaps mean vagus nerve, the tenth cranial one?
    Although I like the vegas name better, more suggestive.
    Maybe the name is different in horse anatomy?
    Haha no, you're right- it's the vagus nerve. But a Vegas nerve does sound like much more fun



  14. #14
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    Quote Originally Posted by alterhorse View Post
    Well, first I'd want to try to understand exactly what may be happening internally in the esophagus of the cribbing horse. and compare that to normal swallowing to see what parts of the esophagus might be involved.

    Would there be any evidence of esophageal stretching caused by cribbing, more so then in normal swallowing?

    Could the equivalent of a barium swallow be done for a horse to observe what normal swallowing looks like, then compare the effect swallowing has on the esophagus, and compare that result to the effect that cribbing has on the esophagus.

    This would be my first thought, to prove there is actually something that can be focused upon, and then try to understand if it's physiologically posable for that location of a horses body to effect the horses pleasure centers.

    One might count the number of nerves in this area, and compare that number between cribbers and non cribbers.

    Or perhaps, one could do a nerve block to this area, if it's posable to do one that won't effect the horse ability to swallow, and then see if the horse stops cribbing.

    I think just proving that it's hereditary, and what the exact cause is, would have to be done before one could consider the remedy.
    I think the Nicols and McGreevy study could answer our questions. There was video of both cribbers and non-cribbers swallowing. From the inside.

    How would one prove its hereditary? And if you did, does knowing the which genes caused what part to be more fun really matter? Applied Animal Behavior Science is more then pure science. Its has a goal. Each of you very good ideas are worth a paper on their own merits.

    I sort of think if we all mostly agree that cribbing is something we would prefer not to deal with, then stop breeding cribbing horses. Regardless of talent. Let the hows and why die out with them.

    If that is not going to actually work then pin-pointing the mechanism might help develop more effective treatments.



  15. #15
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    Quote Originally Posted by equinelaw View Post
    There is also less opportunity to crib. Is there any proof that confinement causes stress, that stress causes cribbing or that cribbing relieves stress? How does one objectively measure stress?

    The answers to these questions are on COTH threads from the past.

    Lets say its all true. How would we prevent cribbing in future horse populations?
    I think what I find most interesting about the premise, is that cribbing might somehow simulate the same pleasure center as eating does, only cribbing might provide a more intense sensation for the horse than actually eating would.

    I'm tying to imagine what preexisting part of a horses physiology might become somehow mutated to explain the cribbing behavior.

    I think it's also posable that the location of this mutation may be in the horses brain, perhaps the brain is essentially receiving normal nerve signals from the esophagus, but amplifying the reception of their intensity.

    I'd suggest the analogy to alcohol and drug addiction in people, as it's believed that some people become addicted to alcohol or drugs because they have a much more pleasurable response to the substance then the majority of the population does.

    If it's true, and it's genetic, the location of the Gene might be locatable, and horses screened for the Gene before before being bred. But it's hard to speculate on cures before the cause is fully understood.



  16. #16
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    I would not be surprised if we find a connection with OCD in humans and in other animals, like horses or dogs, that are very bad about them also.
    Border collies are the poster child for those problems in dogs.

    If we find more about the mechanism in any one specie, I expect the results may translate to others.



  17. #17
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    Quote Originally Posted by Ghazzu View Post
    Decrease in cribbing activity in horses when opiate blockers (naloxone) is given was shown years ago. (Dodman and Shuster)
    Don't think it was esophageal stretching, though, but the behavior does trigger endorphins.

    The tendency to crib is inherited, but tends not to be expressed until the horse is stressed.
    I did hear about the opiate blockers being affective, and I find it interesting how that could factor into the theory under discussion.

    I'm tying to find the reason why the weird mechanical flexing of the horses neck and the air gulping could cause endorphins to be triggered, and I thought perhaps it's somehow being triggered by the same part of the nervous system that eating and swallowing affects.

    I think we might all be able to agree that most horses find eating pleasurable.

    If a person were to put a spoonful of something delicious in their mouth. chew it, and then spit it out, would they find that as pleasurable as swallowing the food after chewing it?

    Perhaps the sensation of swallowing food is part of the overall pleasure of eating?



  18. #18
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    Quote Originally Posted by equinelaw View Post
    I think the Nicols and McGreevy study could answer our questions. There was video of both cribbers and non-cribbers swallowing. From the inside.

    How would one prove its hereditary? And if you did, does knowing the which genes caused what part to be more fun really matter? Applied Animal Behavior Science is more then pure science. Its has a goal. Each of you very good ideas are worth a paper on their own merits.

    I sort of think if we all mostly agree that cribbing is something we would prefer not to deal with, then stop breeding cribbing horses. Regardless of talent. Let the hows and why die out with them.

    If that is not going to actually work then pin-pointing the mechanism might help develop more effective treatments.
    Thank you, I will try to find the Nicols and McGreevy study online and see how the results might be applicable to this idea.



  19. #19
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    Quote Originally Posted by Bluey View Post
    I would not be surprised if we find a connection with OCD in humans and in other animals, like horses or dogs, that are very bad about them also.
    Border collies are the poster child for those problems in dogs.

    If we find more about the mechanism in any one specie, I expect the results may translate to others.
    I also like to think of how some a form of obsessive compulsive disorder might be a factor in cribbing behavior, and it's certainly worth exploring as a cause as well.



  20. #20
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    The ennervation to the stomach and digestive system is in reality our very important primitive brain.
    There seem to be more dopamine receptors there than in our brain in our head, if or how that is relevant, we don't know.
    Those areas communicate very intensively, so it would not be surprising to find some kind of feedback loop around those connections being part of some of these phatologies.

    Over the years we had the ocassional broodmare cribbing on the top of fence posts and it was not because of any inadequate management with them, as they were healthy, on good native grasses, in very large, miles long pastures, with other mares and foals and no grain.



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