It's not just cow versus rodent (although I think that is important nutritionally), it's also the organ meat, bones, and hair that contain vital nutrients and minerals. Snakes need the whole animal for full nutritional value.
The Intuits were able to survive almost entirely off meat (whereas the Europeans quickly got scurvy without fresh fruit, a commodity lacking at the North Pole) because they prized the organ meat (chock full of important nutrients) and gave the nutritionally worthless steak cuts to the dogs.