To see if your cat(s) likes raw, try giving him a piece of raw chicken, or what ever meat/protein you're fixing for yourself (assuming you're not a vegan or vegetarian), and see how they react. If the raw food you feed is less than 15% of the total food you feed your cat, then you don't have to supplement.
There may be an additive in the dry or canned food that your cat can't tolerate.
There may be an additive in the dry or canned food that your cat can't tolerate.