I have never had a newf, but when we got Max, my wolfhound, he was on purina and had loose stools. We switched him to Nutro, same thing, not runny, just really soft and loose. We switched him to Blue Buffalo, holistic or something. Still soft, loose stools. We switched to Innova Evo, same thing. All of this was over the course of a year. I finally changed everybody to raw and we have had nice firm stools, consistently, since then. I can feed complete meals of liver, kidney, gizzrds, etc., with no loose or runny stools at all. It is so nice.
Kathy