As nasty as it seems to us, poo eating is obviously very common in the animal world and for good reason.
Carnivore poo (ie, dogs/cats) is full of protein - dogs and cats have very inefficient digestive systems so a lot of what they eat goes right on through. Also, a lot of dog foods are corn based, and corn is not digested all that well either, so dog poo is rich in protein and also may have a lot of partially digested corn in it also. Gross to us, but a delicious buffet to chickens.
We all know about the bad parasites and bacteria that can be present in poop, but did you also think that poo is very high in PRO-biotics too? Many young animals eat the adult poop as a source of positive bacteria to colonize the gut and make digestion more efficient, so eating healthy poo (not loaded with parasites) can be good for the chicken's digestive health.
Herbivore poo is extremely rich in partially digested grasses and other plant materials. As we all know, chickens have to grind up food in a sac full of rocks before digesting it - eating cow or horse poo is just a short cut for them.
Animals eating poo is the natural world's ultimate recycling. And when you get the circle of poop eating - ie dog eats chicken, chicken eats dog - that's recycling at it's finest. LOL
Scatology lesson over for today....now back to your regularly scheduled programming....