Your ducks can be perfectly happy and healthy without it, but most like to give them niacin from day one until they are grown.
Here is all the info I have:
Sometimes Pekins and larger ducks need more since they are heavier.
Common Niacin supplements
(Not all supplements will have the same as the ones in the pic)
Brewers yeast
2 tblsp = 10mg (50%)
Nutritional yeast
2 tblsp = 56mg (280%)
Vitamin B complex
Niacin
1 ml = 20mg
Liquid vitamin B complex supplement
Niacinamide*
1 ml = 100mg
Depending on how much is in your feed will depend on how much you will need to give everyday.
*"Niacinamide vs Niacin:
Niacinamide (aka nicotinamide or nicotinic acid amide) is derived from niacin. The body has the ability to convert niacin to niacinamide. However, there are some critical differences between these two vitamin B3 components. Niacinamide can also be made by our body from an amino acid known as tryptophan.
Although the two are used interchangeably, they have different properties. Their physical effects on the body also differ, and people who are sensitive to their effects may prefer to use one over the other."
https://martinswellness.com/wellness-connection/niacin-vs-niacinamide.html
"No-flush niacin lives up to the no-flush part of its name because it isn't providing the body with any niacin.
I also recommend staying away from extended-release niacin. Instead of delivering a big bolus of niacin, it generates a lower, steady dose of the medication for hours. Although this eases flushing, it keeps blood levels of niacin high all day. The liver never gets a break from processing niacin, which has led to cases of severe liver damage."
https://www.health.harvard.edu/news...-niacin-as-effective-as-other-kinds-of-niacin
Dumor brand chicken feeds have the minimum requirement of 55mg. Someone else posted that Purina brands do too.
Purina flock raiser does too.
Making sure that your feed bags manufacture date isn't more than 3 months old is also important, since the older the bag the less the vitamins and nutrients will be what they say they are on the bag.