Well, I'll be honest and say I don't like fermented feed in general for birds. Someone
here on BYC had to help their friend in the middle of the night when their birds started suddenly dying. A necropsy confirmed it was the fermented feed that did it.
Birds don't pass food directly to their stomachs like we do, it sits in their crop for awhile first. And it will continue to ferment in there - and grow mold, if mold spores got into the feed. And it can get moldy if left out for any length of time before the birds eat it. And for ducklings that need access to food at all times since they are growing and need to be able to eat whenever the mood strikes, that would mean leaving fermented feed out for them in their warm brooder constantly, which is the perfect environment for mold to start growing.
So in general I'm not a fan of fermented feed. Others may feel differently, but if it's done wrong it can and will kill your birds, as was verified by the lab report that verified that it was the fermented feed that killed the flock I mentioned above.