Our chickens are at 75 degrees w/heat lamp in the brooder, and are mostly feathered out (except for their heads) at 4 weeks. When do you think we could put them out in the top portion of our chicken tractor, without a heat lamp? We were thinking the fully enclosed portion with the ramp in the upright position would be warmer for them at least for a week or so, until they got used to the outside temps. Our temperatures here are 50 degrees at night, 60-70 degrees during the day. Here is our tractor.