Coprophagy is the scientific term for "eating feces." It is not really a sign of nutritional deficiency or illness but most often an unfortunate habit that puppies develop out of instinctive behavior to keep their sleeping area clean. It is not really a risk for the puppy excepting when intestinal parasitism is present then in effect the puppy is reinfecting itself. There is a product called "Forbid" which can be added to the puppy's food. It alters the proteins in the feces and creates an unpleasant taste. You can also try adding a sprinkle of unseasoned meat tenderizer to the food which can accomplish the same thing.