Some dogs really do eat poop - it could be something lacking in their diet or just because the poo was left to long. I have used pills, powders and sour apple they didn't work for me the vet suggested I get some meat tenderizer and place on their food, with in a couple days the poo eating stopped. (this was not in my poodles - but either way) Also pick the poo up quickly.Brian ate poop when I first got him, he was 12 weeks old and from a reputable breeder. Some dogs like poop.
I gave him pineapple - it makes the poop taste bad lol. he eventually grew out of it/really hated pineapple flavored poo.
is the puppy chewing the base of his tail? ... could it be anal glands or fleas?