There is a very productive and cold hardy (10 F) leafy green called 'Tyfon' of Holland Greens. Cross between stubble turnips & Chinese cabbage, Brassica rapa. 40 DTM, high yielding.
It was originally bred for forage and cover crop use, but the young leaves are tender enough for human salad. Very mild, no 'mustard oil' so even cows milk has no mustard taste. Cut-&-come-again every 35 day if cut 1" or more above soil level.
I don't know if it would be practical for goats.
