I am definitely no expert as this was our first time but we have used nutrolac and I am very pleased with it, no runs from the pups and Mum loves it too. We gave it with the eukanuba to our bitch before to tempt her to eat as she got very fussy just before the pups were born....no such problems now though!
I've ordered Nutrolac from Berriewood - it's coming tomorrow. My pups have been loose on Lactol and Welpi, so I'm hoping this will sort things as it is goats milk based. That doesn't really answer your question does it lol because I've never tried Skinners! I think what I'm trying to say is that I personally would steer away from cow's and towards goat's milk. I have heard much better reports all round recently on goat's.