While I know very little about cat food, I do know that you cannot look at just the nutritional analysis where it says how much protein, how much fat, etc. That doesn't tell you what kind of protein it is. The pet food recalls of 2007 were because of a chemical called melamine which mimics protein - so a pet food with melamine in it would test just as high as a pet food with actual meat in protein levels.
There is a thread here somewhere that gives the example of mixing motor oil, shoe leather and sawdust and the resulting 'nutritional analysis' from that mixture. If you looked at just the nutritional analysis, then you wouldn't realize that the mixture is nothing but motor oil, shoe leather and sawdust.
Here it is:
Say you’ve got a pair of old leather boots…
some used motor oil… and a scoop of sawdust.
Now, grind them all up… blend them together…
and send that whole concoction to a food testing
laboratory… for analysis.
And the results? This toxic medley of rubbish
Livin in a Newfie Drool Zone