The Collie brings agility into the breed ie they know when to make a kill and when not to. You ever sin a collie x on the lamp , when it just stands there looking at bunnies on the hedgerows and you and the dog are about 100 yard away. They know soon as they get in feet of the bunnies there guna bolt straight in the warrens so there using there heads. Now ive sin whippets with the turbos on thinking there guna get there before the bunnies have time to bolt back down ,and then stood over warrens used all that energy for f**k all.