DO NOT hit the dog in any case. Thats because they DO NOT KNOW what they've done wrong and by hitting them will make matter worse. Please don't use any physical punishments towards your pet. He/she will have a bad impression on you if you keep on hitting him/her. To stop the dog from eating the poo, just simply say 'aaa..aaa' or 'NO!' and praise him if he doesn't eat it. Give the puppy a pat for his/her well behaviour. You have to do that many times until your puppy understand the message. My puppy used to eat rabbit's poo too as if its her candy and i found it really disguisting. So, everytime i take her out, i keep an eye on what she's sniffing and say 'aa..aa' before she sniff the poo and praise her afterwards. It really worked. Now, she knows that i'm watching her every move.