My last dog was over 100lbs and had an 'abundance' of poop. I switched him to Natural Balance Limited Ingredients and it made a noticeable difference and he did very well on it. I'm currently feeding Diamond Naturals Grain Free and I'm really happy with it. Cas has been on it for almost a year and looks wonderful! There are certainly other grain free kibbles that are 'as good', but it's trial and error with some dogs.
'If you find a way to enjoy the ride, it doesn't really matter where you end up'
5 GSDs at the gate: Katie, Iroc, Red, River, Jake