Mo. Rev. Stat. § 537.260: Railroad liable for killing stock — irrespective of negligence unless road is fenced.

When any animal or animals shall be killed or injured by the cars, locomotive or other carriages used on any railroad in this state, the owner of such animal or animals may recover the value thereof, in an action against the company or corporation running such railroad, without any proof of negligence, unskillfulness or misconduct, on the part of the officers, servants or agents of such company; but this section shall not apply to any accident occurring on any portion of such road that may be enclosed by a lawful fence, or in the crossing of any public highway.