I have tried every trick in the book to stop Josie from doing this. She is (luckily) very selective and only eats Suki's poo!!!
It never ceases to amaze me the lengths she will go to in order to get to Suki's poo before me. The only way I can stop her when we are out on walks is to keep Josie on the lead until Suki goes and then pick it up. The only problem is Suki is one of those dogs who has to go as far away as possible to poo in private
So off I go, over the field, frantically searching for it with Josie on a tight lead or she will snaffle it up before I even see it!!! Mind you, it is an excellent way of finding it in leaves or in the dark - I let Josie find it then grab it before she does.
I have tried putting pineapple in Suki's food - Josie loved it.
So all I can say is good luck and hope something works for you.
Josie has an excellent "leave it command"! - except when there is Suki poo to be found!!!