I think raw is best, but it’s takes a bit more effort. I get some on mine, like chicked wings and heart etc, from the supermarket as it’s cheaper than from the pet shops. I but tripe and minced lamb and beef in 1lb packets, 40 at a time from a local supplier and keep them in a freezer in the garage that I just used for dog and ferret food. This time of year, they get rabbit and hare too, with Pidgeon mixed in.