I have had a very severe diarrhea problem with one of my fillies for a year now. I FINALLY got her better, and it wasn't any one thing that did it I don't think. Things to check FOR SURE: sand in the gut. Get that cleared out. If you don't know how to check yourself, or have the vet out, just get your baby on some psyllium product like sandclear or something like that for a while. The first time I had my filly's belly x-rayed, she was full of sand and I had her on sandclear for a month.
Probiotics: Biosponge is the best, but any probiotics will be good as long as they have live cultures.
Ulcers: I treated my filly for 2 months, this did make a little bit of difference, but I was still in big trouble with her after the two months.
Chinese Herbal Medicine: If you have the availability of someone who really knows their stuff in this regard, this did help my filly also. The vet in this area that incorporates it into his practice is very very good. He studies in China, he is a board certified vet that incorporates western medicine with chinese herbal medicine, accupuncture, and chiropractic. We still weren't quite there with my filly after a month and a half on this.
I did the next things on the list pretty much at the same time. I was desperate, I was really going to lose this filly, she had been down for too long:
Isolate her, no friends, so I could monitor everything happening with her.
Diet: she is on timothy hay only, 1 dry cup beet pulp soaked and 1/2 dry cup LMF TACO (Timothy, Alfalfa, Corn and Oats) soaked given twice daily. Strongid C daily dewormer. And some drops formulated by the treatment person below:
Bicom Bioresonance Therapy: She had two Bicom treatments. This is one of those "magic" things that I have no way to describe. I didn't really believe it would help, but I was totally desperate. Well she had her first fully formed poo the day of her first Bicom treatment. The practitioner also formulated some drops for her food based on the therapy she was given.
All I can say is that I FINALLY have this problem licked. My filly is fat, spunky, full of energy and bright. No more diarrhea. I am so thankful. She is back in with a friend now and holding her own. I wish like heck I had a before picture but I didn't get one. Here is her after:
Forgot to mention that you can also give Pepto Bismol and that might help.