Make sure he is always hydrated, lots of hay, and gradually tighten your girth.
TuffRock G.I (Gastro Intestinal) is fantastic. It naturally works to help prevent stress stomach ulcers and has so many other benefits.
Ulcer Gard works great, but there are many other supplements that could help. Contact you vet and see what they recommend!
Talk to your vet. Maybe there is a supplement that could help prevent ulcers