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I had an idea few years back for a species of "cow" living in arctic/tundra climate which could forage on "anything"- in their habitat it would be mostly vegetation, wood and remains of dead animals including bones. Clay or small rocks should work too if they include some useful minerals. They would be domesticated and fed any waste the humans would produce. They would probably be very strong, but slow, with slow metabolism similar to a sloth. These traits aren't absolutely necessary though. My question is, is it possible (and viable) to have digestive system capable of digesting almost everything? If it can exist, what effect would it have on animals biology and behavior? Some magic can be included but I would like to avoid that. The animal doesn't have to evolve naturally, but it has to be able to survive for many generations.