The board of supervisors of Shasta or Trinity County may, if it determines that all or any part of the county under its jurisdiction has ceased to be devoted chiefly to grazing, provide by ordinance that estray animals may thereafter be taken up on unenclosed property in the county or part of county under its jurisdiction. It is the intent and purpose of this section that the provisions of law which are generally applicable throughout the state shall be extended to all of the county when the conditions upon which the exceptions were based have ceased to exist.