I've never had a ferret become aggressive because they are raw fed, I do have one who nips but she always has, didn't change whether she was fed kibble or raw. Mine picked up eating mice off the one original girl who would, eventually 5-6 of the others would eat mice fine, once they had that down any whole prey was game although mine barely touch large rats. They love mice, quail, guinea pigs, rabbit, chicks. You don't want to feed just one prey item though, you want variety or it will be incomplete.