Why do dogs eat their own poop?

They never say. Most whys about dogs are guesswork. I go along with diet. However, even if it is diet, large breed puppies are better off on a diet they find too skimpy and lean. Such a diet slows growth and allows more time to develop sturdy joints. Better to have a however disgusting but largely harmless habit as a puppy, than bad hips.

If you can make cleaning it up before they have a chance work, it is the best thing. You can add pineapple juice or canned pumpkin to their food, or the commercial products Forbid and Deter.

Most puppies go through a phase of eating everything in sight. The medical term for dogs eating stool is Cophragia (sp?). They usually outgrow it with the help of their owners. You need to keep an eye on the dog and redirect his/her attention away from the stool or anything else he/she may be tempted to eat or taste. If it is it's own stool and is in the yard, as labman states, it should be picked up and disposed of. The suggestion that labman has made regarding the foods mixed in with the dogs diet, also helps with deterence.