Purina start and grow is low on protein for ducklings. Here's a chart. Keep in mind flock raiser isn't perfect for all ages, nothing is, but it strikes a nice balance that will work for all ages.
http://www.metzerfarms.com/NutritionalRequirements.cfm?affiliate=undef&CustID=22059600
http://www.metzerfarms.com/NutritionalRequirements.cfm?affiliate=undef&CustID=22059600
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