
Just wanted to add that Cat Litter depending on the kind and what is added to it to deodorise is poisonous, and there will always be some clinging to the poos so please find somewhere dog inaccessible for the litter tray.
Poo eating is a perfectly natural adaptation to recycle nutrients, and of course bitches do it to keep the pups nest clean and hide their presence from predators. Some bitches are loath to give up the behaviour especially if the pups are being fed high protein food and not digesting it for some reason. Pups learn to do it for the same reason.
It is disgusting to us, but dogs are naturally scavengers and will eat the most disgusting things if there is some nutritional benefit. That is why it can happen if they are lacking something in their diet, or not digesting it properly.
Then you have behavioural reasons, such as hiding the evidence of their crime, attention seeking etc.
The best way to stop the behaviour is to not allow it to occur which means vigilance and cleaning up as soon as they eliminate, if it is their own of kennel mates at home.