Ulcers will indeed cause a lack of appetite. Stomach ulceration can be painful and lead to nausea. While dogs often vomit with ulcerations, cats usually do not. Sometimes hiding behavior, slight decrease in activity or appetite is all that is seen. Sometimes the clinical signs are more dramatic.
Christopher A. Lee, D.V.M., C.V.L.S.
Promoting surgical options and pet comfort through the use of lasers.