To reduce the risk of spraddle leg, you will want to avoid slick flooring in incubator trays, transport carriers, and brooders. Also, do not use newspaper or cardboard flooring for the first week of their lives. The best bedding is wood shavings, straw, or � inch hardware cloth floor. To prevent leg injuries, you will want to avoid slick surfaces for adult birds, too.
You can learn how to treat spraddle leg here.
Duckings walking safely on wood shavings in their brooder
You will also want to avoid surfaces on which ducklings and goslings can cut their feet. Circulation is not great in waterfowl feet, and a minor cut can lead to a nagging, swollen infection.
Especially with baby ducks, you'll want to make sure that the floor surface is flat and does not have any depressions that can cause them to fall, land on their backs, and not be able to get back up. If they spend too much time on their backs, they may develop spraddle leg.