A while ago, I had two dogs, a big happy golden retriever and a Jack Russell. The golden used to follow the Jack around and eat his poop, drove me nuts. I tried smacking his nose, yelling at him, anything I could think of. Didn't matter, the golden kept eating the terrier's poop.
I decided to call the vet. He said, "Oh yeah, this does happen sometimes. But don't worry, I can prescribe this spray that really works."
I'm skeptical. "Really? A spray? Do I spray it on the golden's nose as a deterrent?"
Vet: "No, you just follow the little guy around, and when he poops, you spray it on the poop. And be generous."
Me: "Ummm... and how does that work?"
Vet: "Simple! The spray makes the poop taste bad!"
Obviously this guy never owned a golden retriever...