Niacin for ducks (in feed)- how much to give?

[Funky Feathers]

I bought Niacin 500mg capsules for my ducks. How much should I give each duck (they weigh 5-6 pounds)? Please respond asap. Thanks

 

[dot n'dave]

You can add 100 mg per gallon of drinking water. Dont give them too much.

 

[Funky Feathers]

OK, so one 500mg capsule (powder) in a 5 gallon bucket of water. Thanks.