Coprophagia is when a dog or other animals consume their own poop or that of other dogs or animals. Some claims that lack of some nutrients is responsible for this behaviour. I will tell you that puppies that are being fed with high quality premium dog food can still engage in this act.
The simple way to stop the behaviour is to add blended succulent part of pineapple to the food of the dog. Mix a little portion of the blended pineapple with the food thoroughly. When the dog eats the mixture and it is digested, the resulting poo will have an unpleasant taste and the dog will not find the poo palatable again. If you add the pineapple to its food for some days, the dog will see its poo as unpleasant thing to eat. Also there are some drugs in the market to curb poo eating in dog.