Withholding food helps reduce the amount of possible poop and semi digested food mess during butchering. Choosing a best practice that doesn't involve using a knife too close to the intestines will help minimize risks too. Such as with quail just pulling apart the rib cage from the back. As animals pass away they can defecate and you could cause some to come out during butchering possibly contaminating your work surface and the meat. Not ideal to do it but if you have no choice, have some bleach and paper towels on hand and be ready to clean should any poop show up. It is definitely doable.