Probably 4 or 5 times a week I get an email or phone call from someone who is struggling with an off the track horse with an over active mouth. The symptoms can include (but are not restricted to) excessive chewing of the bit, picking it up with the molars, pulling the tongue back, putting the tongue out, putting the tongue over the bit, pulling the lips back, opening the mouth, etc.  The chewing and over active mouth in the off the track thoroughbread (OTTB) is very, very common.  It is often a very ingrained behaviour/ habit and often related to stress and not actually strictly related to the particular bit in the mouth.  The OTTB simply associates the bridle and bit with stress, no matter the situation and this can show in the mouth with fussing and fiddling.

Thankyou to a facebook fan who sent this picture for illustration purposes.

Riders often say their horses get their tongue over the bit, but in reality this is actually fairly rare.  It is more common that the horse draws his tongue up and back, and it bulges over the mouthpiece without actually falling all the way over.  Obviously this is not ideal, as the tongue is a big muscle and drawing it back not only adds tension along the neck and back, but also restricts the airways.  (which is one of the reasons why the use of a tongue tie is so common in racing, to improve performance in a horse that does this by keeping the airways clear, as well as maintaining control).

In saying that, a fiddly fussy mouth is more often than not related to the back.  If the horse has any back issues, it can show in the mouth, or if the horse is not correctly through and over the back, it can also show in the mouth.  Most riders will comment that the horse is better towards the end of a workout than at the beginning- as the horse works more properly through and develops a better connection from back to front, the mouth quietens in response.  The same applies to the hollow backed horse that is hesitant to drop his poll and take a contact.

Changing this behaviour will take time and patience, as it is often something they have been doing for many years.

Things to check first- if the bit is sitting high enough in the mouth.  If the bit sits too low, it will sit on a thinner, more sensitive part of the tongue or hit the canine teeth repeatedly.  Do not look at the wrinkles, look inside the mouth.  Ideally the bit should rest halfway between the canines and the molars.  Moving the bit a little higher temporarily can help re train the mouth as it makes it harder for the horse to play with.

Also check the correct size- if the bit is too big, again it will droop in the mouth and sit too low.  If the bit is too thick, he will be unable to comfortably close his mouth at all.

Be sure his teeth have been recently (within the last 3 months) checked to be sure there are no issues there, and the same with his saddle fit and back health.

Consider his diet, the possibility of ulcers, if he has been let down appropriately before the start of his re-education.

Video your training sessions and work with your instructor to critically assess if the horse is correctly through and forward (not rushing) and tracking up, and if the back is lifted or hollow.

Consider changing to a copper alloy mouthpiece, as this is a great conductor of heat, meaning the mouthpiece becomes very warm in the mouth and not something cold and foreign to inwardly fixate on.  This can help improve the general acceptance of the bit. Something like the bits below may help:
%%GLOBAL_ShopPath%%/sprenger-dynamic-rs-eggbutt-40414-88/
%%GLOBAL_ShopPath%%/neue-schule-tranz-angled-eggbutt-snaffle-8023e/

Another bit that I have found that suits the TB mouths quite nicely, though it is a loose ring, if the Team Up:
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Or, mullen style as this gives the horse even less to play with and move around.   By taking away some of the gratification and distraction can help the rider improve the behaviour through training:
%%GLOBAL_ShopPath%%/nathe-standard-snaffle-bit-1786/

There is no easy, quick solution to retraining this behaviour.  It requires a holistic approach, as the symptoms of the fussy mouth are just that- symptoms of other problems.  Giving an OTTB a chance at a new life after racing is wonderful thing, but some can offer more of a challenge than others.  I wish that I had a magic bit that would make this job a lot easier for everyone, but I just don’t!  As with most things with horses, patience and consistent correct training is the key to a good result.