Mo. Rev. Stat. § 272.290
Whenever the fence of any owner of real estate now erected or constructed, or which shall hereafter be erected, constructed or rebuilt, the same being thereafter a fence designed to restrain swine, sheep or other animals requiring special fences, borders the land of another or which becomes a part of the fence bordering the land of another and is used to enclose such animals owned by the other person, on demand made by the person owning the fence, the other person shall pay the owner one-half of the value of so much thereof as borders his land, and upon the payment shall own an undivided half of the fence; except that no owner shall be required to pay more than the amount which would have been required to erect, construct or rebuild a lawful fence of four barbed wires on his one-half of the fence.
§ 272.290, RSMo