Neurohormonal regulation of feed intake and response to nutrients in fish: aspects of feeding rhythm and stress

The regulation of feed intake is very complex and involves interaction among the circadian and homeostatic control systems within the central nervous system, the gastrointestinal tract and the environment. The hypothalamus, which receives, integrates and transmits relevant internal and external signals, is recognized as the primary centre of regulation of feed intake. The neuroendocrine factors that originate from the hypothalamus either stimulate or inhibit feed intake so that nutritional demands of the organism can be fulfilled and energy balance can be achieved. Appetite regulation is a physiological mechanism in which a variety of neurohormones interact and fish show different feeding behaviour (e.g. diurnal, nocturnal). This complicated system is very sensitive to any disturbance. Fish in farms and fish in a natural environment are equipped with the same combination of neurohormones to regulate feed intake, but they meet different challenges, particularly with regard to the type of feed and feeding schedule. In this review, the neurohormonal regulation of feed intake is analysed in fish in terms of entrainment of their circadian feeding rhythms and while exposed to different stressors in captivity.