Feed intake is the central issue in animal husbandry, being the key factor in determining health, welfare and productivity. This is the focus of this text, which has been developed from the 5th Zodiac Syposium held in Wageningen in April 1998. It reflects research in observing natural behaviour and investigating form-function relationships, physiology, metabolism and genetic makeup, and by offering choices of feed and environment. Information from studies on humans, wild birds and fish, as well as farm animals, is presented.