We live in the country and have rabbits running all over the place...which means they poop all over the place.
2 of mine seem to think rabbit coco puffs are a delicacy and it is nearly impossible to keep them from finding them.
While neither have been negatively affected by it...we also don't live in an area where poisons are used.
I would absolutely do everything in your power to prevent them from eating ANYTHING they find outside.