I have heard that flax seed is not a good ingredient in dog food, especially breeding bitches. I can't remember why though, is flax seed a phyto-estrogen?

I agree with your issue and would likely still raise pups on Proplan. In that instance price is not a issue and I have no beef with Proplan.

I'm just looking for feedback on the 4 health, good, bad or indifferent.

I googled it and can't find anything but good things to say about flax seed in the canine diet, great for coats