A. When livestock is injured or killed by a locomotive or cars on the line of a railroad unfenced by good and sufficient fence or other barrier sufficient to turn livestock, the railroad is liable in damage to the owner of the livestock unless it is shown that the owner or his agent or servant immediately contributed to the killing or injury of the livestock.

B. Livestock straying, or grazing unattended by a herder, upon unfenced parts of the railroad is not contributory negligence of the owner.