Question: I own a stout rescued mustang. He is very responsive when he chooses. My main problem is that he gets his tongue over every bit I've tried. He's properly fitted. I don't know if he needs a different bit or if I should ride him in hackamore or a combination. I can't take him on the trail as he some times gets his tongue over, and he can buck and leave the country. What do you recommend? I'm not sure if it is a comfort issue or just a habit.
Answer: The issue of bitting can be a complex one. Ultimately the horse does have the final say, since he has to wear it. Since bits are made from metal they can be hard and unforgiving.
The very first thing to check when you have a bitting problem is the teeth. Have you had a good floating job done in the last year? Most horses need about a yearly schedule, but some need it more frequently. A well-done job cannot be accomplished in five or 10 minutes. On the other side the use of power tools to float teeth can and is often overdone, leaving the horse with an unbalanced mouth that can cause problems for a long time while the teeth grow and wear back to normal. Power tools can be very useful, but care needs to be taken. Many dental technicians and veterinarians fail to round off the front of the teeth enough to be comfortable where the bit sits.
Horses who get their tongues over the bit are usually expressing discomfort of some sort. Often that discomfort is from too much pressure on the tongue. Also horses who fuss constantly, stick their tongue out of their mouth and open their mouths are expressing discomfort. Occasionally these habits become so ingrained that the only solution is to remove the bit, but in many cases you can figure out the problem and solve it with a different style mouthpiece. Also, check your noseband. You should be able to slide a couple fingers between the leather and the nose; if you cannot the nosepiece is too tight. If your horse opens its mouth or does any of the other behaviors above, do not tighten the noseband, look for the source of discomfort.
Once you are sure the teeth are not a source of discomfort, then you need to look inside the mouth at the tongue. How big or small does the tongue look? If you open the mouth and see a large tongue leaking over the edges of the teeth, there is little room for a bit, so you will need a thin mouthpiece. A few of those horses will never be comfortable with a bit. If you try to put a thick mouthpiece in this situation often the horse cannot even shut his mouth all the way. The shape of the roof of the horse's mouth (the palate) also helps decide how much room there is for a bit. A flat palate means there is less room, while an arched palate leaves plenty of room.
A horse with a small tongue can handle a thick mouthpiece and may even appreciate it. A thicker mouthpiece can have a gentler edge against the bars, but if there is no room the thicker bit is worse.
Next to consider is the type of mouthpiece. The commonly-used snaffle bit exerts a downward force on the tongue preventing swallowing when rein contact is being taken rather than pushing up into the roof of the mouth as is traditionally believed (see illustration). Obedient horses who can tolerate the tongue pressure will basically keep their heads in the correct "frame" or position for the sport you choose with only minor moves to swallow. Horses ridden with a loose rein will be able to swallow in any bit since there is no pressure on the tongue other than the weight of the bit. Most horses will try to escape the tongue pressure by either putting their noses up in the air or ducking "behind the bit" in order to swallow.
Bits with a port or curved mouthpiece can be much more comfortable and offer relief to the tongue (drawing port bit). Several companies now manufacture bits with creative mouthpieces. Myler was the first to offer a line of bits that really looked at mouth comfort and ability to swallow. Now many other bit companies have curved mouthpieces that relieve tongue pressure. Dr. Hilary Clayton has done a study on the effects of bits on the mouth.