Q: I bought a horse at auction with an unknown training history. When I rode her, I found that she’s saddle broke but has an incredibly hard mouth when ridden in a snaffle. Any time I put pressure on the reins, she responds by pulling 10 times harder. She’s difficult to steer and stop, and don’t even think about trying to “collect” her or set her head. What can I do to soften her mouth and make her more responsive?

A: Horses develop a hard mouth for many reasons, including pain, stress, and learned behavior. To resolve the problem, consider each possible cause, starting with pain.

Is your horse experiencing discomfort or pain?

A veterinarian can determine if your horse’s resistance to rein pressure is due to pain. Checking the oral cavity is an obvious first step; a problem as simple as sharp points on the molars can lead to painful ulcers of the buccal membranes (the inside lining of the cheeks).¹^,² Poorly fitting tack can also cause discomfort. A bit that doesn’t fit properly can cause bruising and ulcerations on the bars and corners of the mouth² and a tight noseband (sometimes used to prevent the horse from evading the bit) can impede breathing and cause bone microfractures.¹

Tack-fit issues should be evaluated by a veterinarian or experienced trainer, who can make informed recommendations about equipment (for example, trying a bitless bridle or different bit). In general, avoid using mechanical devices, such as a severe bit, draw reins, or martingale, which may offer a short-term solution but won’t ease discomfort or teach the horse to respond to a light hand