My 2 year old sheltie was exactly the same, we tried pineapple and it didn't work. So we supervised her when out and told her off if she went near poo, picked poo up regularly and when out unsupervised we put a basket muzzle on her. She isn't half as bad as she used to be, once they stop doing it for a while they tend to forget about it, it's a matter of breaking the habit. Here are some points from an article I read not long ago by Keith Allison (www.bahnm.org)
Coprophagia - Eating excrement
Autocoprophagia - an animal eating its own faeces
Intraspecific Coprophagia - eating faeces from another animal of the same species
Interspecific Coprophagia - eating faeces from another species
There's no simple explanation as to why dogs to it, there could be many reasons. Although we find it revolting it doesn't usually do the dogs any harm and can sometimes be beneficial.
There are many theories:
1) Underlying medical problem - pancreatic insufficiency, pancreatitis, intestinal infections, malabsorptive syndromes and over-feeding (especially high fat diets). Though Coprophagia is probably not the only symptom in one of these cases.
2) Coprophagic dogs may be lacking in natural micronutrients such as vitamins.
3) They find the chemical appetite enhancers found in some dog foods attractive, despite having been digested by the dog.
4) If a dog is not fed fresh meat or ’wet’ food the dog may be attracted to another dog that is.
5) The dog is trying to introduce beneficial bacteria into their digestive systems, as most dog foods are almost sterile.
Behaviour theories:
1) Attention seeking - The dog is rewarded with the owner’s attention when it eats poo.
2) Coprophagia is also associated with allelomimetic behaviour - where the dog observes the owner picking up the faeces and learns to do so as well.
Cures:
1) Food additives: Pineapple and other citrus fruits, pumpkin seeds, peppermint, papaya and aniseed.
2) Garnish the faeces in something like vinegar or spring onion juice - something the dog doesn’t like.
3) Clean up faeces regularly.
4) Put the dog on a lead and let him sniff the poo and growl ‘No’ at the dog. When the dog pays no attention to the poo praise the dog.