If feeding anything other than starter they will need chick grit . They have to have a way to grind up anything other than starter and chick grit is what works.
Since I have a mix flock of chickens ducks and a goose I buy chicken feed and add nutritional yeast for the extra niacin. I start out using chick starter /grower and once they are laying age they all eat Layer. My Muscovy have always done real well on it. Chicken feed doesn't have enough niacin...