Mont. Code Ann. § 81-8-313

When the copy of the process or instrument, with the proper notice appended thereto, is filed as hereinbefore provided, it has the same effect as if actual possession of said cattle and horses had been taken by the officer or person charged with the execution of such process, or the party required under said instrument to take the same, and shall continue to have such effect until actual possession of such property has been taken or had by the officer, person, or party aforesaid; provided, that such actual possession be had or taken prior to August 1 next succeeding.