‘Coprophagia, to give the proper name, is a natural form of behaviour which most dogs learn from puppyhood when their mother will clean up after them.
It happens more in puppies which come from rescue kennels and pet shops. It can also be started by poor house-training where owners do not clean up after the pup.
Boredom is another cause. Dogs that spend long periods alone in the garden or in kennels can develop this habit.
In kennels, dogs will copy other dogs doing it. Don’t rub a dog’s nose in its excrement. This only teaches dogs to eat the evidence to avoid punishment. Don’t shout or chase the dog away. It will only learn to eat faster.
Remove the faeces or douse them with tabasco or peppers. The dog will not find that taste very rewarding.
It could be the dog is just hungry.
Split the daily food ration into several portions and feed the dog three or four times a day with a higher fibre content.
Alternatively, the dog could have a health problem. There is a condition called exocrine pancreatic insufficiency, where a lack of enzymes in the pancreas will result in dogs being ravenously hungry.
Dogs suffering from this will eat anything. Although the eating of faeces is absolutely repellent to humans, the smell and texture is attractive to dogs. If all else fails, only allow the dog off lead with a muzzle.