Teaching your horse to open his mouth is useful in many instances, from bridling to husbandry. Once you’ve taught your horse this behavior, you’ll find it much easier to check his teeth and to perform routine worming. It also can be an excellent tool if your horse has an accident that requires you to regularly examine his mouth or perform regular dental care.
If your horse is head shy, please begin your training by reading about Horses Who Are Head Shy  and helping your horse overcome his fear.
The following are basic guidelines for teaching your horse a new behavior, such as opening his mouth on cue:
- Take it slow. Move slowly, and don’t try to teach your horse everything at once. You’ll be teaching him his new skill in small steps that are geared to help you and your horse succeed.
- Be patient with your horse and yourself.
- Let your horse see what you’re doing as much as possible.
- Let your horse know when he does what you want and then immediately reward him so he’ll repeat that behavior.
Please read this entire article before you begin training your horse to open his mouth, and keep the guidelines above in mind as you progress.
Recognizing and Reinforcing the Behavior You Want
Reinforcement is the strengthening of a particular behavior by following it with a desired consequence. In this case, “desired consequence” means that when your horse does what you want, you reward that behavior with something he wants. The reward is the consequence of his good behavior.
The first step in reinforcing behavior you want from your horse is to help him recognize when he’s doing the right thing by telling him so. You can say “Yes!” or “Good boy,” or even give a quick whistle to point out his good behavior. The sound you use doesn’t matter that much. What does matter is when you make the sound. You want to “catch” the behavior you desire from your horse while he’s doing it, not after he finishes. The sound draws your horse’s attention to what he’s doing at the exact moment he hears the sound. Catching behavior this way makes it memorable to your horse, and making it memorable helps him associate your reward with his behavior.
Steps to Teach Your Horse to Open His Mouth
Your goal when training your horse to open his mouth is to teach him that when you give him a cue of some sort, like a hand signal or the instruction “Open up,” he should open his mouth. But if you start with a horse who clamps his mouth shut when he sees the bit or the wormer, that goal seems a long way away. You can, however, reach that goal by taking small steps and rewarding each step as if it were the ultimate goal. Your horse will think that learning is fun, and soon he’ll be opening his mouth whenever you ask.
Step One: Teach Your Horse to Be Comfortable with the Cue
You begin by teaching your horse to be comfortable with your cue. A useful cue for asking a horse to open his mouth is to touch two fingers—your index finger and middle finger—against the side of his lower lip where it rests against his bar area. (The bar area is the area inside his mouth where there are no teeth.) To teach your horse to be comfortable with this, simply reward him just for letting you touch the area—and give the reward while you’re still touching him. For the reward to be associated with your finger touch, the order of events should go exactly like this:
- Touch your horse as described.
- Say “Yes!” to associate your touch with the reward.
- Give him a treat (with your free hand) as you take your fingers away.
Step Two: Teach Your Horse That the Touch of Your Fingers Brings Treats
- Begin with your horse tied or otherwise secured in cross-ties. (Later, after he’s learned to open his mouth while tied, you can teach him to do it while he’s loose in his stall.) As always, be certain that your tie system includes a panic snap or quick-release knot.
- Approach your horse’s head on the near (left) side by walking toward him from an angle that aligns with his left eye and right ear. Turn so that you’re still on an angle but you’re almost facing in the same direction as your horse. (You’ll actually be facing his left nostril.)
- Put a treat in your left hand. Raise your right hand—the hand closest to your horse—and hold up your index and middle finger, just like you did before.
- Say “Open,” and gently press the two fingers against your horse’s lower lip, centering them between the front of his lips and the corner of his mouth.
- Say “Yes!” Then take your fingers away and give him a treat. Repeat these steps four or five times.
Next you’ll teach your horse to open his mouth. This won’t be too difficult. He’ll be expecting treats because you’ve just been giving them to him for letting you touch his lips. Say “Yes!” when the gentle pressure of your fingers makes your horse drop his jaw, even a little bit. Your “Yes!” will catch his jaw drop so he learns that it’s the thing he did to earn his treat.
Step Three: Teach Your Horse That Opening His Mouth When You Touch Him Brings Treats
- Say “Open,” and press the first two fingers of your right hand against your horse’s lower lip, just like you did in the steps above. As you press, maintain slight but consistent pressure, and move your fingers so they go just under his upper lip. You don’t need to press hard at all—you aren’t forcing your horse’s jaw down. When he opens his mouth, quickly say “Yes!” to catch the movement of his jaw, and then take your fingers away as you give him a treat. You can also praise your horse and tell him how smart he is. Repeat this step four or five times.
- Say “Open,” and press your fingers against your horse’s lower lip. This time, hold your fingers in place until he opens his mouth far enough for you to see light on the other side. He might open his mouth a bit and then close it—but don’t give up. Just calmly hold your fingers in place until your horse opens his mouth enough for you to see light. The instant that happens, say “Yes!” Then take your fingers away and give him a treat. Repeat this step four or five times.
Now you’re ready to teach your horse that he has to open his mouth wide enough to let you put something inside. And presto! He’s trained!
Step Four: Teach Your Horse to Open His Mouth Wide and Let You Put Something in It
For this last step, you’ll need something to place in your horse’s mouth. Two practical suggestions are a bit or a worming tube. The worming tube will go into your horse’s mouth very close to where you’ve been touching him with your fingers, but the bit goes in from the front, so the steps are different.
The bit Select a bit. Make certain it’s wide enough for your horse’s mouth. (It’s fine if it’s too wide.) A curb bit is a good choice because you can hold the shank as you slip the bit in. A solid snaffle is another reasonable choice.
- First, show your horse the bit. Even if he’s fearful at bridling time, he probably won’t react with fear because the bit looks quite different when it isn’t attached to a headstall. But if he seems worried, hold the bit up to his muzzle and let him sniff it or lip it. (Horses like to explore things with their lips.) When he touches it, say “Yes!” and give him a treat. Once he’s okay with you holding the bit near his face, you can start your training.
- Hold the bit at the front of your horse’s mouth with your left hand on the right shank. You should be standing on your horse’s near (left) side, facing him on an angle in line with his left eye and right ear. Be sure to hold your left arm below his chin rather than in front of his face, so that your arm doesn’t spook him. Say “Open,” and press your fingers (right hand) against his lower lip. When he opens his mouth, slip the bit in, keeping it upright and straight so the shanks can’t catch his lips. You might need both hands to do this, but don’t let go of the bit. When you have the bit in his mouth, say “Yes!” Then take the bit from his mouth and give him a treat.
- Repeat the steps until he anticipates your command of “Open” and reaches for the bit when he feels it at his lips.
The wormer tube Teaching a horse to cheerfully accept worming is all but impossible because each time he opens his mouth for the wormer, he’s rewarded with vile-tasting medicine. What you can teach him, however, is to accept something that looks like a worming tube but ends up tasting like peppermint frosting. You can do this by picking up a tube of squeezable mint frosting or by buying a small, inexpensive frosting or cookie press tube and filling it with a concoction made of confectioner’s sugar, water and mint.
- With the filled tube in your left hand, approach your horse so that you’re facing him on an angle in line with his left eye and right ear. Say “Open,” and press your fingers (right hand) against his lower lip. When he opens his mouth, slip the tube in just above your fingers. Squeeze the tube a bit and then quickly say “Yes!” Remove the tube and your fingers, and give your horse a treat. Horses are neophobic—they fear or dislike new things or things that seem strange to them—so your horse may toss his head, flip his tongue or act like he doesn’t like the taste of the frosting paste. Don’t worry—very few horses dislike minty sugar paste. So, after a few experiences, your horse will be quite happy with his training.
- If your goal is to make worming easier, you’ll need to practice with your horse several times per week with the frosting for every one time you actually worm him. If you’re worming him every other month, he should get at least 15 sessions with the frosting tube for one actual worming. But don’t have a frosting paste session right after worming your horse. The wormer will make the paste taste bad, and he may remember the bad taste the next time he smells mint. Then you might have a hard time getting him to open his mouth for the worming tube at all—whether it’s filled with tasty mint paste or the nasty tasting wormer!