This is actually more normal than not. Cats have a short digestive system designed for eating meat. When cats consume a diet that contains other ingredients, especially when the food is sprayed with fats after manufacture so it’s palatable to the cat, the feces will also contain undigested fats. Plus, cat feces have an odor that attracts dogs. Although we find this disgusting, if your dog eats a piece of cat feces once in a while it’s no problem. However, if your dog raids the litterbox filled with clumping cat litter, and does so regularly, that litter can cause a major problem in your dog’s intestinal tract. It will clump, as it was designed to do, but will obstruct and damage the intestines. Make the litterbox inaccessible to your dog and if he gets into that litter, call your veterinarian.