http://cats.about.com/cs/catfood/a/reading_labels.htm
There are a lot of good articles here. This particular link has a formula for figuring out some of the label jargon and numbers.
I went to the link posted below, but it was for Innova food, and just compared various types of food within that brand.
Have a good browse - I found this really helpful!
Catty1
Bookmarks