When we lived on a small farm our dog would eat the cow patties. I think dogs eats **turds,,, i really don't know what word to use** because it is full of vitamins and protiens that they need, that is what I have heard. But it is common for dogs to eat that stuff. If it bothers you real bad I would try putting the litter box in a higher place, one where the cats can jump up to and one the dog can not reach. Just a suggestion.