Abstract: A control system for use with a self-locking pen paneling arrangement includes a series of retaining bars which are movable from a first access position to a first retaining position in response to downward movement of an animal's neck toward the feeding area. A movable locking member is mounted to each retaining bar, and is engageable with a latch member when the retaining member is in its first retaining position. A release mechanism is operable to disengage the locking member from the latch member to provide movement of the retaining bar to its first access position. If desired, the retaining bar can be moved to a second retaining position, distinct from the first retaining position, in which movement of the release mechanism does not disengage the locking member from the latch member. This "locks out" certain animals to prevent withdrawal from the feeding area, to enable the operator to dehorn, vaccinate or perform any other procedure, treatment or operation on the animal as necessary.