The cat who nips at your hand is similar to the horse who nips at (air bites) your hand, and you can use the same methods to stop the behavior.  Keep your hands away from his face; never allow him to play with your hands; and never, ever, physically punish him.

Keep your hands aw0ay from his face.  Most horses either like you or are indifferent to you.  Since humans value emotional reciprocity, if you like your horse—and most owners do—you want your horse to like you.  (Professional trainers don’t care one way or the other.)  Most horse lovers are enchanted by a friendly horse who walks up to the fence at your approach and sticks his head between the bars of the arena, the way Gunsmoke is doing in this photo.  (If he were taller, he would stick his head over the top bar.  He prefers it this way—he can rub his mane out.)   He’s begging you to pet me, pet me!  Often a horse will move away from you, usually along the fence line, until his butt is right in front of you.  Such a horse is asking you to scratch his rump, please.

Horses who literally reach out to you usually want a head rub or scratch, and there’s no reason not to do it—unless your horse is nippy to begin with.  Gunsmoke was an unbroke five-year-old stallion when I rescued him. He didn’t understand how to lead or what whoa meant, and he didn’t understand what you wanted when you asked to pick up his leg (just to be on the safe side he kept snatching it back).  He was opinionated and always hungry.  Gelding him got rid of his testosterone, which made him less aggressive, but he will always be opinionated and eat anything you put in front of him.  While John worked with me in the beginning—as a professional trainer he knew more about unbroke, recently-gelded stallions than I do—he was disinclined to use food to reward good behavior.  Gunner liked his face rubbed—he still does.  In fact he liked physical contact with humans so much that getting brushed after a training session became a reward.  It was after John stopped helping me that I got into trouble.

Whenever I tried to do anything with Gunner—halter him, lead him, sometimes even simply brush him—he would give me air bites.  Not hard enough that I could hear his teeth click, but nip and run—in other words, he’d immediately yank his head away.  When I complained to John, he said, “Then keep your hands away from his face.  When you halter him, stand at his withers and slide the halter up his neck.  When you lead him, don’t hold your hand directly under his jaw.  When you brush his face, don’t brush his lips, and hold the cheekpiece of his halter with your other hand to keep him from reaching for you.”

Don’t let him play with your hands.  Since Gunner was such a friendly horse, I couldn’t break myself of the habit of walking over to rub his face.  One day John watched me hold my hand flat against the mesh wire so he could rub his upper lip against my hand. “You’re making it hard for him to do the right thing when you let him play with your hand like that,” he said.  Should I have known that from my experience with my nippy orange cat?  Of course.  Did I apply it to my nippy dun horse?  Of course not.

Do not physically punish him.  The sad fact is that I was in over my head with Gunsmoke, and for a long time I was too embarrassed to ask John for help again.  I was riding him—no problem.  My problem was his ground manners.  It seemed as though whenever I handled him, he’d try to nip me.  One afternoon I lost my temper.  Instead of returning him to his corral and calling it a day, I snapped off a dead stick.  While I walked beside him, every time he took a swipe at my hand, I “corrected” him by jabbing him in the jaw.  In about five minutes I went from having a horse that nipped to one who was seriously trying to bite me.

Was there a way to fix this problem?  I didn’t know.