The present invention provides an agent for promoting weight gain and/or improving feed efficiency for single-stomached animals or immature ruminants, an agent for reducing diarrhea, and an agent for improving intestinal bacterial flora, the invention being characterized in containing cashew nut shell oil, heat-treated cashew nut shell oil, anacardic acid, cardanol, and/or cardol.本發明提供單胃動物或幼小反芻動物的體重增加促進劑及/或飼料效率改善劑、腹瀉減少劑以及腸內菌叢改善劑,其特徵係含有腰果殼油、加熱處理腰果殼油、檟如子酸、腰果酚、及/或腰果二酚。
