my horse is an 11 year old 16.3 gelding. I have had him for three years, no problems. This winter he has been lacking in energy. After a ride recently he cramped up very badly, since then he is continuing to cramp during exercise, when he is standing he is lifting one or both back legs in a manner that indicates he is in pain. After he cools down he seems fine again. The vet gave me salts to add to his food but the problem persists.