[sillylupie]

I agree with adamyala, it is probably due to change in cat's diet.

I remember my cat, Lulu was having similar problem when she was on Smart Heart, Friskies or Whiskas. When she passed gas, we could hear her from upstairs! It was as loud as a human's!

I wouldn't worry if the cat is still eating, drinking and playing well! From your note, you mentioned a week of vet food, I assumed he was okay (poop and gas wise, hehehe) and it was only until the Friskies, then EVO & RC that the ordeal begins? If so, do check with the vet the brand of kitty food they have been feeding during his one week stay and give the same to him.

Also, do note that it is always very important to introduce new cat food in stages, otherwise there may be bout of diarrhea and gas problem.