Every evening we call the sheep into the barnyard and lock the gate so coyotes don't kill them overnight. Most of the animals come running (we give them a bit of alfalfa). See how fast they run here: http://www.livingthecountrylife.com/videos/v/92276781/the-running-of-the-sheep.htm
A few rebel lambs climb the compost pile, above, and force Bob to shoo them off and chase them around the pile.
An occasional lamb or ewe doesn't come running because her head is stuck in the woven wire fence. (The grass is not greener over there, silly animals.) For this reason, someone has to walk down to the pasture and check the perimeter. Freeing them requires tugging, pulling, and sometimes loss of an eartag.
I took this photo at dusk from the pasture looking up to the barn. That oat field does look inviting.