The Classic Comprehensive Handbook of Cat Care
(GASTROINTESTINAL TRACT): FLATULENCE (INTESTINAL GAS)
Having a flatulent cat around is more of an inconvenience than a real medical problem. Excessive gas formation unaccompanied by other problems can usually be controlled by changing the diet. With a little observation you can often find that flatulence occurs only when a specific flavor or brand of food is fed or only with certain types of table scraps.
Some cats cannot digest oligosaccharides such as raffinose and stachyose, which are carbohydrates contained in soybeans. Since soybeans are a common ingredient in dry cat foods, oligosaccharide- intolerant cats may develop excessive intestinal gas when they are fed them. Oligosaccharide intolerance is similar to lactose intolerance, which occurs when a cat is unable to digest milk sugar (lactose) and bacteria in the gut ferment the excess carbohydrates causing gas production and sometimes diarrhea.
Cats eating relatively poor-quality diets that are high in fiber may also develop flatulence, because diets high in fiber decrease the digestion of nutrients in the small intestine allowing them to pass on to the large intestine where they undergo bacterial fermentation and accompanying gas formation. Flatulence that is not reduced by a diet change and is accompanied by diarrhea necessitates thorough physical examination and treatment directed toward resolving the diarrhea. When the stool becomes normal, flatulence often disappears.