I am sorry but I do not know any, I don't even live in Indiana but I go to a chiropractor, I am going to become a chiropractor, my brother is one and i could go on with the list.
Anyway...what I am getting to, is see if you could find a chiropractor that does humans and see if they would be willing to adjust your horses. Animals, including horses, are built almost exactly alike just animals stand on all four limbs, people stand on two. So for a chiropractor to adjust a horse, it wouldn't be that difficult, if they are a good chiropractor.
An equine chiro near me (sorry, not near you) is also a human chiro. However, I think that human chiros must be certified in animal equine also, or else it is illegal for them to practice on animals. Just something to think about... I could be wrong though.
I was looking to become an equine chiro - and I believe you had to have a vet license 8\ To do it legally. -shrugs- I don't know... I don't think McDavitt would travel that far south - but if you want his number it's worth a shot. If you made it worth his time (more than 6 horses or so)... but I know he requires 2-3 horses around here before he'll come out. Which is bullocks because he still charges a farm call I believe.
I guess you could do that but it will not be the same thing as a chiropractic adjustment. A massage will just get to the muscles and help them relax and stuff like that. When a chiropractor adjusts your horses it realigns all the bones so none of the nerves or anything are being pinched so your horse's muscles, nerves and everything in its body can work as they should. It is kind of hard for me to explain since I don't know everything about it yet.
You need to contact Brad King in Daleville. I will PM you his number. He is the vet that does all the horses at the track in Anderson and is the highest recommended equine vet in Indiana. Pm'ing you now!!