Next 5 days here not above 10 degrees,,,several nites way below zero with wind chills around 25 below. I cannot imagine peas in an outside pen without a enclosure to be locked into if necessary. I would venture to say mid 20's protein feed levels would be minimum if the birds had no protection from the cold wind.And that may not be high enough.
Mine are enclosed, but I still use game bird feed at 28% protein!