Personally I would hesitate to put them in a tractor at their age. Not so much because of the temperature, but because of the spring rain/cold/chill combo.

If they are feathered I don't worry about supplemental heat, but in a tractor they will be on the low damp ground, in cooler weather. Sooo, I'd come up with a different plan, but that's just me. Unless your weather isn't as wet as ours is this time of year?

We have a wire cage hung with wire twine from the ceiling we use when we need it. Maybe something like that would work temporarily?

Brendasue

I've heard after 6 weeks. This is based on starting them at 95 degrees, lowering their temp by 5 degrees every week, and then not needing supplemental heat after they are used to 70 degrees.