The present invention provides a productivity enhancing agent, a wasting rate-reducing agent, an ameliorating agent for ascites, emaciation, or maldevelopment, and a prophylactic or therapeutic agent for inflammation or colibacillosis for use in poultry such as chickens for meat, which comprises unheated cashew nut shell liquid, heated cashew nut shell liquid, anacardic acid, cardanol, and/or cardol.