My source of info is at bottom of page at this link.
http://www.feathersite.com/Poultry/BRKRaisingDucklings.html
http://www.feathersite.com/Poultry/BRKRaisingDucklings.html
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Here is where there are several links and Quotes on this Question.
https://www.backyardchickens.com/t/62320/ducks-and-medicated-chick-starter[/URL
And all that was true 20+ years ago when sulfaquinoxaline was used....it is a vit K antagonist....amprolium is the one commonly used now...it is a thiamin blocker....ducks have the same thiamin requirements as chicks. I rely on actual research data, not
web links. Might want to read Scott and Dean. Nutrition and management of ducks.
Clint