Answer

By Your Horse

Natural Horsemanship Expert Charles Wilson replies:

There is usually a physical reason for a horse resisting in the mouth. I would ask your vet to recommend a dentist to have a look – sometimes a long tooth at the back of the upper jaw presses on the lower jaw, landing behind the lower teeth. This is very hard for dentists to see. Or there may be a deep-seated abscess in the skull. Once this has been ruled out, the other physical factor is the bit. The bit needs to be wide enough to have half an inch showing beyond the mouth, and placed comfortably, with the sides of the mouth slightly wrinkled.
You have tried different bit types – have they been of different materials? Plastic or rubber bits are the softest on the horse’s mouth – then there is vulcanite and various metal types. Many horses like the taste of sweet iron, but it is not as smooth as stainless steel. For your horse, I suggest a simple bit, such as a jointed or straight bar snaffle.
If there are no physical factors, you need to consider tension and lack of trust in the rein contact. If his early experiences were of too strong a hold on the reins, he will have developed a habit of trying to avoid any contact.
Ride with one hand at the buckle and let him have complete freedom. He may well fuss less, which would indicate that he needs more education to accept a bit. He will need a loose cavesson noseband – any tightening on his nose bone will make him feel constricted and resentful. By giving him nothing to lean on, hopefully his habits will subside. Then, over time, you can re-establish a light and giving contact.