PROBLEM TO BE SOLVED: To provide a preparation using a highly safe active ingredient which can improve and enhance the reproductive performance such as the conception rate and the pregnancy rate of livestock (dairy cattle, beef cattle, swine, or the like), and which fully exerts its effect by being administered orally or fed to the livestock, and to provide a method or the like for improving and enhancing the reproductive performance.SOLUTION: By administering trehalose orally or feeding it to livestock (dairy cattle, beef cattle, swine, or the like) as an active ingredient, the conception rate, the pregnancy rate, or the like, are enhanced, and the non-pregnant days, the interval between deliveries, or the like, are shortened； therefore, the reproductive performance can be easily and effectively improved and enhanced.
