The disclosure relates to an agent when used to improve reproductivity of a ruminant that is not suffering from acidosis, the agent comprising at least one of cashew nut shell liquid, which may be a cashew nut shell itself, heat-treated cashew nut shell liquid, which may be a heat-treated cashew nut shell itself, anacardic acid, cardanol, and cardol. The disclosure also relates to a feed for the same purpose and a method of improving reproductivity of a ruminant using this agent.