While you may see a decrease in symptoms just by changing the diet, treatment is still necessary to actually allow the ulcers to heal because a horse's stomach produces gastric acid all the time rather than just on demand like humans. Ulcergard may help reduce symtpoms as well, but it is not a high enough dose of omeprazole to treat ulcers. So, if you suspect ulcers you and your friend should talk to the vet about options for diagnosis and treatment.
Gastroguard (higher dose of omeprazole than ulcergard which is the preventative dosing), ranitidine or cimetadine are the 3 drugs that can be used to treat ulcers.
Free choice forage, remove grains, choose forage based supplemental feeds if needed (senior feeds or especially ration balancers are a good choice), eliminate work load during treatment....
You can go to www.thehorse.com
and do a search for gastric ulcers and come up with tons of articles on gastric ulcers. Here are a couple of them: The Horse: Tummy Troubles: Equine Gastric Ulcer Syndrome The Horse: Gastric Ulcers