I know @Miss Lydia uses nutritional yeast and because of her so do I now. When I refill my feed buckets which is about every 2 days I sprinkle 2 heaping tablespoons of nutritional yeast right on top of the food in each bucket. I don't mix it in so it gets eaten first. I like the olive oil idea though. I forgot to add that my ducks have never looked better which I attribute to the NY
I've been reading a lot of good things about the Nutritional yeast on here. I'm going to switch to that also. I have been using the Fresh Eggs Daily brand of Brewers Yeast with garlic supplement.