Open mouth syndrome

["John & Sue Greenall" <greenall@vermontel.com>]

I have seen several other horses do this, but never got to really 
examine this "syndrome" until getting a horse that did this.  Perhaps 
someone can give me a "scientific" reason why horses do this, Tom, 
are you listening?
The horse works fine at a certain level, but when asked for more, 
opens the mouth while working.  This is not related to a bit as I 
have seen horses do this while on a tread mill and while being 
ponied.  The head usually turns to one side and the teeth are bared.  
Then the mouth opens and closes or sometimes stays open.  If the 
horse is under any duress, it does not show in pulse recoveries or 
lameness.  I have mostly seen this at a canter, but the horse I am 
working with now did this a lot at a trot.  However, as he became 
fitter it diminished, but is showing up again with canter work.  
Most interesting and I would love to know why they do it?
John and Sue Greenall
mailto:greenall@vermontel.com
http://www.vermontel.com/~greenall