In an action for the recovery of the value of livestock referred to in AS 42.30.150, proof of death or injury is conclusive evidence of negligence upon the part of the person or the person's lessee or agent owning or operating the railroad. Contributory negligence on the part of the plaintiff in the action is a defense. However, allowing stock to run at large upon common unfenced range or upon enclosed land owned or in possession of the owner is not contributory negligence. Proof of wilful intent on the part of the plaintiff to procure the death or injury of stock defeats the recovery of damages for death or injury.