Thank you for the advice, Timothy.
I've kept up my search, and from what I have read, it seems that most people start ducks on a commercial chick starter and add brewer's yeast to make sure there is
enough niacin. The ratio is about 3 pounds yeast to 25 pounds feed or 2-3 cups yeast per 10 pounds of feed. There are quite a few homemade chick starter recipes to be found, so, what I will most likely end up doing is going with one of those recipes or something similar, and adding the brewer's yeast. I will post my recipe and my results for anyone else who might be interested!