Abstract: In the present study, the immunohistochemical method streptavidin-biotin-peroxidase complex (SABC) was used to examine the effect of energy on serotonin-like neurons in hypothalamus of Cherry valley ducks bred with high energy feed and low energy feed, respectively. All films were analysed by using a computer-assisted image analysis system. In high energy group, labeled cells are widely distributed in paraventricular nucleus(PVN，17.73±1.41 neurons/19.46×103μm2) and ventromedial hypothalamus (VMH, 15.80±1.71 neurons/19.46×103μm2). In low energy group, labeled cells are widely distributed in lateral hypothalamus(LH，11.25±1.53 neurons/ 19.46×103μm2), yet none in PVN.These results indicate that serotonin-like neurons in hypothalamus are involved in the regulation of food intake and energy metabolism.

Key words: Cherry valley duck, Serotonin, Hypothalamus, Food intake, Energy metabolism