Good thing is most cats outgrow the nasty farting stage (kittens seem to get it when moving on to solid foods). Go with a good brand of catfood- Science Diet, Purina Proplan, ect- not the supermarket brands. Slowly switch brands over a week or 2 or you may make the farting worse. Look for brands high in protein and lower in fiber. Also avoid corn fillers- rice is better. Also avoid wet foods