In cases of inadequate maintenance, dogs eat their own defecation, often for reasons of master reprimand and excessive hunger. A dog who is excruciated by the master is afraid and even thinks that excrement is wrong, and next time, he/she eats his/her own excrement in order to destroy evidence.
If dogs are not fed regularly for a long period of time, resulting in over-hungry, the dog eats its own shit in order to feed. The best way to feed a dog is to eat less than one meal a day, leading to hunger.
All we have to do is give the dog a rational diet and the dog doesn't have to eat his own shit. Every day, the dog is fed regularly, occasionally with a small snack, supplemented with nutrients of various kinds, and the dog has no desire to eat poop.