I just don't think I'm understanding completely.
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I checked Zupreem and the protein is 40% and fat is 20% which is the exact same as most high quality grain free cat foods. Cats and Ferrets are both carnivores which get everything they need from the meat bones and organs of their prey and need no plant matter in their diets.
You'd feet cats and ferrets the exact same diet if you did raw which would be 80% muscle, 10% bone, 5% liver and 5% other organs with plenty of heart. Since thye have the both dietary needs theres really no difference. Evo used to make a cat food and a ferret food and they exactly the same foods, but with a different name on the front of the bag.