"Slow grow is the way to go" ....I have seen so many newfs encounter unnecessary difficulty when with owners who are so "anxious" for there gentle giant to be ...well giant...so hard on the joints.
I have had several newfs over the years and our most recent is Wesly ..a beautiful 7 month puppy. We feed Innova adult maintenance and include every day fresh fruit, veggies, and a raw chicken neck cut into small bite size pieces (bones and all ...great source of calcium). We also suppliment with canine metabolizer (Malpleton).
I should also mention we have a long haired dachshound(Howard)who had terrible skin allergies ...nothing seemed to work to relieve the itching...it was heart breaking. Then our vet picked up a new partner who specializes in pet nutrition and suggested we switch from corn based foods....many dogs are allergic to corn... Anyway, she suggested we switch to California Natural (rice and lamb are the only ingredients) ..and Howard now looks great ...his coat is beautiful, no skin allergies ...no scratching.. no licking (and thankfully...no more weird shampoos, dips, lotions, potions, whoodoo or voodoo...a happy little puppy!!!!!
I web site that discusses most major brand kibble ingredients is
http://www.iei.net/~ebreeden/kibble.html
Exciting waiting for that puppy isn't it ...silly as it may sound I lost sleep at times waiting for our most recent addition