Why did my dog suddenly eat feces?

Dogs eat feces because they are both predators and scavengers. There is nutrient material in feces of some animals, and people, that the dog can digest and use. Cat food has more fat and protein than dog food does, and cat feces contains nutrients a dog can use. So do human feces. It is very likely that man did not purposely domesticate wild dogs, but that the dogs who were confident enough to get closest to human settlements, where they could eat discarded food and human feces, were the ones who fared the best and reproduced successively more human-friendly offspring. Dogs can contract internal parasites from eating the stool of other animals. Dogs do not eat their own feces unless they have enzyme deficiencies that prevent them from completely processing their food, so that their feces still contains undigested nutrients. Enzyme supplements like Vet-Zyme, K-Zyme, Pro-Zyme, or sprinkling Adolph's Meat Tenderizer onto their food, solve this problem for most dogs who eat their own stool. A basket muzzle with a stool cup will foil the dog's attempts, but it cannot drink or pant with the stool cut in place. For some dogs, it can become a vice with no medical cause. It is because they eat feces (this is called coprophagia) that some cultures consider dogs to be "unclean".