From my understanding you would measure by weight not volume.
I just gave a new home to some older ducklings, about 11 weeks old. Trying to get a better understanding of the dosing for the brewer's yeast at this point. Will ask on another thread. Since I do not know the content of niacin it...
Good to know the about using weight instead of measure. I have not gone that far into my research. We plan on trying to grow our own feed eventually, so I have been doing research.
Remember every percentage will change, not just the protein, when you add something.
Here are a few links that may have the answers you are looking for:
http://babel.hathitrust.org/cgi/pt?id=coo.31924003011545;view=1up;seq=1...