At Grassland Dairy, Wentworth, Mo., cows wait to be milked in a round holding pen. The design is something that the producers brought with them from New Zealand. The holding pen is gently sloped from the outside edge toward the center. A drain located in the center of the circle leads to a nearby lagoon. After the last cows enter the parlor, the entire holding pen is hosed down by simply turning the water on and letting the backing gate rotate around the pen.