If you're inclined to experiment, "Tyfon" or "Holland Greens" are a very-fast-growing , high-yield-per-square-foot forage crop that is good for "cut-and-come-again". You could expose it to the chickens every 30 days or so.
You could also let it grow large (up to 60 days) and then cut and haul leaves to feed them.
It is VERY cold-hardy once established, like down to 10 F.
