Coprophagia is seen more frequently in puppies but most eventually outgrow it. Puppies may indulge in coprophagia as harmless investigative or playful behavior and owners must be cautious not to inadvertently reinforce the behavior by giving the puppy additional attention when it consumes feces. Pets that are underfed or placed on an overly restricted diet may have a voracious appetite which may also include coprophagia. Pets that have been overfed, and those with gastrointestinal conditions such as malabsorption or trypsin deficiencies may have higher amounts of undigested ingredients remaining in the feces. These feces might then be palatable enough to appeal to some dogs. Similarly, horse and cat feces can be particularly appealing to some dogs. It is commonly thought that inadequate exercise and environmental stimulation may make a dog more likely to consume its own feces.
The ultimate cause of coprophagia in adult dogs has always been elusive. Some feel that the problem is behavioral, while others are convinced there is an organic reason. Soft stools, incomplete digestion of food within the stools, evidence of steatorrhea (fat in the feces), increased stool frequency or volume, or a voracious appetite might indicate a problem with maldigestion or malabsorption. Other gastrointestinal disturbances such as inflammatory bowel disease, systemic health problems including renal failure and endocrinopathies (unlikely in an otherwise normal 7 month old), medications such as glucocorticoids (prednisone, e.g.), central nervous system diseases or any disease process that causes polyphagia (increased hunger) might lead to picas (eating non-digestibles) and coprophagia. Calorie-restricted diets, especially those that are not balanced or do not adequately satiate the dog may also lead to picas including coprophagia. Recent research has suggested that there may indeed be a medical component to the problem in some cases. In a small study of nine coprophagic dogs, all had at least one laboratory abnormality that could explain the problem. The laboratory profile included a complete blood count, complete biochemical profile, amylase, lipase, trypsin-like immunoreactivity (TLI), vitamin B12, folate, fecal fat, fecal trypsin, fecal muscle fiber, trace minerals including zinc, selenium, copper, iron, magnesium and boron, and fecal sedimentation (an ova and parasite exam). Most had borderline to low TLI (suggesting pancreatic exocrine enzyme deficiency/a lack of digestive enzymes produced by the pancreas) while others had abnormalities in folate, Vitamin B12 or other nutrients.
As you can see, it might be wise to have blood work performed by his vet. Please respond with further questions or concerns if you wish.