I don't know about feeding cats raw, but I have been feeding my dogs a 100% raw diet for a while now. I chose not to feed any commercial foods at all, the reason I changed to raw was I was not happy with the ingredients in commercial, so there would be no point feeding half and half if you see what I mean. From all I have read, raw and commercial should not be fed together as the different digestion rates can make the animal uncomfortable. I've known people that do do it, and their animals have been ok, but how do you know if they are feeling overfull and uncomfortable? Like if you have a big roast and you feel like you've over done it? I think it's similar to that.
It may not do any major damage, but I'd avoid it myself

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