Equine chiropractors are pretty mainstream nowadays. The one I use is an excellent vet to start with who also does adjustments. There's wackos out there, but there's definitely some properly trained individuals who do a lot of good. I get my mare done every other year or so. Her back gets sore, it's super obvious when you're riding her, the chiro comes out, and she's so much more relaxed and moves more freely when I get on her the next day. A year or two later, she's sore again and we repeat.

Crap, even the old school Kansas cowboy I used to ride with uses them. When his ranch horses start acting sore, he gets a chiro out. The man can do pretty much anything else veterinary himself, and does, but calls in an equine chiro for his working animals.