The dog digestive system is remarkable.

Dogs put food in one end, then put poop out the other end, and sometimes eat the poop one more time just for good measure.

Exactly how the dog digestive system works is a bit of a mystery.  Humans, for instance, do not need to digest poop (food) a second, third, or fourth time.  Yet canine digestive systems all seem to keep telling their canine mouths/noses/legs/heads to seek out poop and digest it.