I have found that “distraction” can be a very handy tool when faced with something painful, uncomfortable, disliked or unwanted.
For example, when your animal is about to get a shot, scratch their ears or whatever their favorite itching spot is, and scratch them a little bit harder than you might normally. The trick is in the timing – start scratching them just a moment before the needle goes in. This approach will divert their attention to something they like, and because you are scratching with more pressure than usual, their total attention will be engaged — the shot will be given before they know what happened.
With the girth issue, you have a routine of A) attaching it on one side, then B) going to the other side to tighten it. When you do “A” she is anticipating “B” and gets ready for her response – biting you. Therefore, your goal is to stop her from doing “B” — said another/better way, you want to give her a ‘new and improved’ step “B.”
So, try changing that routine:
0) Before you start: put a piece of bailing twine through the ‘other’ buckle of the girth (the buckle that will be attached later), so you can position the twine on the ground under the horse in order to easily pick it up when you move to the other side of the horse. By doing this, your action of reaching for the unattached end of the girth will not be detected by the horse. You can slowly pull the twine until the buckle is in your hand and then remove the twine.
1) attach the girth to the saddle as you normally do; move the twine so it ready for you to pick it up on the other side
2) fiddle with something else on that same side (maybe pull the stirrup down and put it back up again),
3) pat her on the neck or wherever her favorite spot is
4) go to the other side and pat her on a favorite spot
5) fiddle with the saddle pad or something else
6) pick up the end of the twine that is attached to the girth while fiddling with something, scratching her leg or asking her to lift her foot (YOUR OWN MIND is focused on whatever you are fiddling with – reaching for the girth, in your mind, is just something extra to do. Your mindset here is very important – she WILL read your mind.)
7) gradually pull the twine until the end of the girth is in your hand. Scratch her with more pressure on her neck, chest, her leg or find something very interesting on her hoof
8) place the buckle of the girth at the last (loosest) hole of the billet, but do not attach it. (If she goes into high-alert, keep the end of the girth in place, don’t move. With your other hand, fiddle with something else, scratch her somewhere else, until she relaxes a little and you can see that her attention has shifted. Don’t get frustrated if it takes a while — this is the part of the routine that you are trying to change and thus the hardest part of the process.)
9) attach one buckle to the loosest hole of the billet, give her a rewarding pat or treat, provided she doesn’t try to nip
10) go on to whatever you do after attaching the girth, or do something else that is not associated with the girth – pick out her feet, groom her some more, etc.
11) while doing these other things, and with YOUR MIND focused on those other things, sneak in the step of attaching the other buckle to the loosest hole of the other billet, give her a rewarding pat or treat, provided she doesn’t try to nip
12) follow the same approach to tighten the girth, one buckle at a time, one hole at a time. Take it slow, distract her with something she likes.
A few questions for the behaviorists out there.
~~ Step 8: (Other end of girth has been positioned at the billet and ready to be attached.) If the horse does not relax, and if ‘lovehorses’ is not able to divert her attention, should she back off and a.) let the girth drop away while holding the twine, b.) return to earlier steps, or c.) Press on? How long can she wait for the horse to relax? (As Clint Eastwood says, “A man’s gotta know his limitations.”)
~~ Step 9: (Attaching the buckle to the billet.) Concerning the notion of rewarding good behavior and not even acknowledging bad behavior — if the horse does try to nip (I’m thinking it would not be as aggressive as usual given attaching the buckle is happening unexpectedly) is it OK to ignore the nip and then reward a good behavior as soon as she can?
Hope this is helpful to you. I know it’s long and detailed, but . . .
“On Target Training” or “Clicker Training” might be something you can learn more about. Here is a link to the Search Results for Shawna Karasch, a true guru and trainer.