People, please understand that chiro's can have as little as 5 HOURS of training and that can all be ONLINE. They are simply not a substitute for a veterinarian. They have NO medical training unless they are also a veterinarian. There are no requirements for training for calling yourself and equine chiropractor, education and certification can be granted by anyone who can print a document using their computer.
In a situation where there is a problem with your animal you should always have a veterinarian perform a physical exam to rule out that there is some medical condition that needs treatment. Then consider a chiropractor if a back issue is diagnosed.
And don't count on people from an online forum to tell you if something isn't likely to need veterinary care. What everyone missed in this post is one of the classic descriptions of a horse tying up. This horse needs to be examined by a veterinarian within 12 hours of one of these episodes so that blood work can be run to see if that is in fact what is going on. (The changes in the blood that indicate muscle damage start to return to normal after 12-24 hours. So blood needs to be collected during that time period.) And any pattern to these episodes needs to be looked for as well. It may be a dietary issue, a metabolic issue or a poor conditioning issue if it is indeed tying up. http://www.thehorse.com/pdf/factshee...p/tying-up.pdf
Get a vet exam and if your horse is not tying up and your vet can't find a problem then consider a chiro but don't try to use them in place of a veterinarian.