My parents have an older female Great Dane that does this, and they have tried almost everything possible to stop her. The vet recommended hot sauce (like Tabasco or similar) on the poop at first, but after that failed they tried a vet product called Forbid. It's a powder that's mixed into the dog's food, I believe. Anyway, even that didn't work, and the vet was stumped. Now my folks are just resigned to having to follow Lizzie around when she goes outside and cleaning up after her IMMEDIATELY!

The vet did say that most dogs can be cured to some extent, but some dogs never stop. It's not known why they do it, either.