Section 3. The writ shall require that the bond be given for double the value of the beasts but shall not express the amount for which it shall be given. If the parties do not agree as to the value of the beasts, it shall be ascertained by three disinterested appraisers, who shall be appointed and sworn by the officer, and the penalty of the bond shall be double the value ascertained by such appraisers or by a majority of them.