I really do not. I was told it years ago and honestly it could have just been to get me to keep me and the dog from eating cat food (i was a stramge child). I've used it before for birds too, but just a tiny bit spread over time, and they haven't shown anything bad, but they didn't live off of it
So, if I remember right, cat food can be bad because it's got some type of sodium or something that most animals aren't really supposed to eat.
Is there a reason you didn't get another bag when you started getting low? It just seems odd you waited until you were almost completely out/were out...