I do not know about Kalmbach but if it is formulated for ducklings it should be fine. I have used Manna Pro. It is ok. Personally I prefer Purina duck for mine, for life. I would encourage you to rethink switching to chicken layer feed. Several years ago, my ducks were on Manna pro duck layer and my feed store stopped carrying it. They told me chicken layer feed would be fine. After six months I was as having trouble with rubber eggs and feather quality. I switched to Purina omega chicken layer with only minor improvement. Then, they started carrying Purina duck. After only a month or so the rubber eggs went away and feather quality improved. It has now been a couple years without issue. I will forever stick with food formulated for ducks.