Don’t over do all you need it liquid b complex give your duckling 1 ml a day over something yummy like peas or dried mealworms. Putting it over something yummy keeps it from being watered down and you can make sure he is getting full dose. @Rudinsfarm2018 id actually give it any ducklings you have if feeding chick starter. Or buy Nutritional yeast for the ones not showing any symptoms. It won’t hurt your little patient in having it along with liquid b complex. NY is 1 Tab per cup
