Things like raptors or snakes that swallow prey whole do so to get complete nutrition. Feeding them something like chicken breast for example, only would provide the nutritional content of lean muscle protein. They wouldn’t be getting calcium from the bones, minerals from the different organs, fats from skin, and the water content from the whole body. Each body part holds specific things that are needed for the predators (and the prey when it was alive) to survive. So the simplest way to feed them is to feed them as close as possible to how they’d eat in the wild.

I don’t feed all the carnivores we have just mice though. Each animal is getting a customized nutritional plan based on their species, weight, and current state of health. We have baby chickens and baby quails and other whole animals we can give them. And some mainly eat fish, so we occasionally need to stock whole fish as well. We just need to keep them functioning as close to how they would in the wild as is feasible.