Some dog eat poop and for dogs this is totally natural, for us this is totally gross. About the only thing i could do to stop one of my dog from eating her own poop was to be standing behind her with a pooper scooper and get it before she could turn around. Drove me insane! Because she never did it before she had puppies. But i guess they drove her to do this and then she got hooked. :p
Walk him on lead, pick up ASAP and correct him for even looking at crap.
I'm not Nutro's biggest fan, 5.5 cups a day a is a heck of a lot of kibble. Try a higher quality food and feed less. Maybe this will stop.
Or you can try "Forbid, Distaste or SEP (stop eating poop) which are food additives that are suppose to make poop taste bad. But don't you think poop should taste bad already?
This could be a by product of a few things. Food not giving enough nutrition. Bad habit from his previous owner, comes from a line of crap eaters, yes it does run in some lines.
Better supervision is the cheapest answer.