Many cuddly and not so cuddly animals eat shit on a regular basis. (Remember that next time
Poochie wants to lick your face). These include rabbits, rodents, gorillas, and
man's best friend the dog.
Rabbits, rodents and their ilk eat shit because their
diet of plants is sometimes hard to digest efficiently, and they have to "make two passes at it to get
everything out of the meal." Also, the bacteria in an animal's colon produces certain vitamins and minerals that Fluffy just can't resist. "The animal is unable to
absorb the vitamins through the intestinal wall, but can get at them by eating the poop."
Now you may be saying to yourself, "That's fine for a rabbit, but why is my dog eating cat shit?" Well, the answer is good old fashioned protein. Apparently, cat scat is a high protein food and has a taste that dogs just love. So if you're the resourceful type and not too squeamish, you might never have to buy kitty litter again.
Source : Brenna E. Lorenz (a vet who lives in Guam and therefore has plenty of time to study this shit)