Coprophagia, or the eating of feces, can have several different causes. It is extremely difficult to pinpoint the exact cause of this unwanted behavior. Causes may include:
Boredom;
Attention seeking;
Exploration;
Feces that taste good;
Poor hygiene;
Acquired habits;
Mimicking the mother, who often eats the feces of her puppies before they are weaned, to keep the nest clean.
So the causes can vary widely. A nutritional deficiency is almost never the cause, provided, of course, that your dog receives a well-balanced dog food and does not exhibit any gastrointestinal problems.