Here's a good article on niacin supplements and niacin deficiencies.Oh ok got it! I am using non medicated chick starter - I’ll give the duckling niacin with that. I only just realised that it’ll take two weeks for the nutri drench to come so it might not be an option anymore, for the time being I suppose I’ll see how the duckling is once it’s dried up and see if it needs anything more
https://www.backyardchickens.com/articles/niacin-deficiency-in-waterfowl.75862/