What are you feeding your flock currently?
Food.

Sorry Abi, quotes messed up.
I wouldn't think so. All flock feed has enough niacin for ducks/ducklings, according to people I trust. Since it's meant for feeding to chooks too, not just ducks, I doubt the extra niacin hurts them.
Duh! Can you tell I haven't had babies in a while? Thank you. I can't believe I forgot!