It shall not be necessary for any person to fence against any of the species of animals enumerated in the petition that has been adopted, and it shall be no defense to any action or proceedings brought or had that the party taking up stock did not have his lands enclosed with a lawful fence. However, nothing in this section shall be construed to lessen or interfere with the obligations of the railroads in this state to fence the right-of-way of the railroads as is provided for by law.