Nov 11, 2008 — If you're in the market for bull DNA, this Heard Up North is for you. Artificial inseminators criss-cross the North Country everyday, servicing dairy farms. In the back of the truck, they carry an injecting gun and a tank of liquid nitrogen that keeps bull semen chilled at negative 320 degrees. David Sommerstein caught up with one breeder while he was - literally - up to his elbow in a cow.