What story does Weston tell the lamb in the kitchen?

While in the kitchen in Act Three, Weston talks to the lamb that is inside. Weston tells the lamb the story of the day he is castrating lambs and an eagle keeps swooping down. Weston realizes the eagle is trying to get the discarded testes, so Weston throws the testes on top of the barn each time and watches the eagle swoop down and grab each one.