Has the vet ruled out medical issues? Good article here : http://www.aspca.org/pet-care/virtual-pet-behaviorist/dog-behavior/coprophagia-eating-feces (excerpt below)
Medical Problems to Rule Out
Starvation, Malnutrition or Malabsorption Disorders
If your dog isn’t getting sufficient food or isn’t able to digest the nutrition in his food, he may resort to coprophagia as a way to supplement his diet. Before doing anything else, it’s important to have your dog thoroughly examined by a veterinarian to rule out medical problems that could cause coprophagia.
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