reducing protein in feed

[TLWR]

What can I add to the feed for the ducklings to reduce the protein.
They eat an unmedicated 18% protein chick starter. They run the deck or are in a brooder in the yard or free range in the yard for an hour or so. The plan was to construct a 12x12 pen for them to hang in during the day in the yard instead of just in their brooder in the yard.

 

[Speceider]

Not certain why you want to reduce the protein....most all-flock feeds are 18%. Many will say cut with oats, but that screws up the ME of the diet and throws the amino acids out of balance.

Clint