I know this is your cat but my dog, 6 years old, is recovering from IBD. Traditional western medicine (large doses of Flagyl, then Prednisone among the things tried) did not help one bit and in desperation we turned to a Holistic Vet who has helped others we know of, and with our usual Vet's blessing. His recovery diet is cooked ground turkey and cooked sweet potato with varying assortments of "11 secret herbs and spices" mixed in.
I mention this only for your consideration.
My own 17 year old cat has been eating cooked hamburger (strongly advised against for my dog though, at this time, too fatty). She also dabbled in the dog's turkey till all of a sudden the darn grocery stores started putting rosemary extract in it and now none of the cats will touch it.
They must put a lot in, I can smell it myself.
More good thoughts.