PITTSFIELD, Maine - The Balfour Farm organic creamery operation, about 40 miles south of Bangor, is just over a year old. It sits on 100 acres of pasture, where 20 Jersey, Normandy, and Holstein cows graze. Owners Heather and Doug Donahue, both 38, decided to become full-time farmers and set their sights on Maine. Heather Donahue says they found the state “a haven for dairy farmers.’’ The Donahues typify the new breed of young agricultural entrepreneurs who come to farming from other fields. Heather was a middle-school science teacher in New Hampshire and Doug worked in construction. They started off as hobby farmers with a single cow grazing in their back yard acre. Today their 1835 white clapboard farmhouse is attached to a new creamery and milking rooms.