...Why?

In researching the Newfoundland breed, we knew what to generally expect as an end-point, but there was a distinct lack of information about how fast they attained their tremendous size or what they looked like along the way. We sought to remedy that. (A gain of 2.5-3 pounds per week seems to be about right, as it happens.)

Another thing the Internet lacked was a straight-forward to how much these things need to eat. The following is from our vet, so of course does not constitute medical advice for your dog, but it's what ours has been given since he was nine weeks old and he seems to be doing just fine.

Calorie needs for Giant Breed Puppies (> or = to 55-60 pounds) are as follows:
Resting Energy Requirements (RER): [30 x (weight in pounds / 2.2) ] + 70 = xx daily kcalories
From 6 wks - 4 months : kcal needs = RER x 3
From 4-12 months : kcal needs = RER x 2
12 months through 18 months : kcal needs = RER x 1.6
>= 18 months adjust as indicated based upon activity / lifestyle

I put it into a spreadsheet and then just update the weight field as needed, like so:

Weight in lbs
Resting energy requirements:	=SUM((30*(B1/2.2))+70)
4-12 months	=SUM(B2*2)
kcal from treats
Cups Holistic (375kcal/C)	=SUM((B3-B4)/375)