I have an Appaloosa that is an incredible trail horse. He is getting older these days (around 16) He is one of those horses that could eat himself to death. During the summer we have to watch how long we put him out to pasture so that he doesn't founder himself. I bring this up to mention that he is pretty overweight right now. We haven't had the time to get out and ride him very much during the last six months. Here is what I know, I took him out on a trail ride back in October. This was the first long trailer ride (2 hours one way) he had been in about 10 years. When we got to the trail this horse had the runs (diarrhea) really bad. At the time I equated it to him being nervous from the long trailer ride and in unfamiliar circumstances. I have since been able to only ride him 5-6 times since then and I have been noticing his diarrhea still. It is extremely runny and I am really worried about his health. We feed him alfalfa hay, he is fed the same thing as the other four horses he is with who all seem to be fine. What would you recommend, I give him?