Balancing protein levels?

[Angelove]

Thanks in advance for considering my infinite number of questions...
I am raising my ducks for pets/eggs, not meat production, which I understand means that by week 3 they should be eating food that is 15-16% protein.
David Holderread recommends you add 5% oats by volume each week until they are eating 25% oats and 75% chick starter/grower by week 5. I don’t understand how this alters my 20% protein food to 16%...I used the Metzer feed mixing calculator as well, which says that to get my feed down to 16%, I would need to mix 1 pound of my feed with 1lb of oats, which by volume is ~3 cups of my feed to 5 cups of oats..
This is over 50% by volume addition of oats.. by Holderread’s recommendations I would be feeing 3 cups feed to 1 cup oats..how/why is this so different?
I would have just followed Holderread’s advice, but after using the feed calculator I am very nervous..I really want to make sure that I am not giving them too much protein/am giving them the correct % so that they live long happy healthy lives..
Does anyone have a better understanding of this than me/experience mixing your feeds to the right protien level and/or can explain why Holderread’s numbers are so different than Metzer’s?

 

[Miss Lydia]

Why not instead of driving yourself nuts you find a good All flock and just feed that. Many of us have fed all flock without any problems at all.

 

[Miss Lydia]

I use to always feed Purina Flock Raiser crumble from hatch through all stages of life til I decided to use a NON GMO feed.

 

[Angelove]

I use to always feed Purina Flock Raiser crumble from hatch through all stages of life til I decided to use a NON GMO feed.

Non GMO is important to me, what type of feed do you use?...After having to do so much math, I am going to try to get a duck specific feed.

 

[Miss Lydia]

I use Natures Crest only NON GMO feed I can get here.

 

[HollowOfWisps]

Kalmbach has a 16% protein maintenance feed that is Non-GMO. Chew.com sells it.