Temporal control of feeding behaviour and its association with gastrointestinal function.

This paper summarises knowledge about temporal control of ad libitum feeding in poultry, from minute to minute, hour to hour and day to day, and about how it relates to aspects of gastrointestinal function. Evidence is presented of only loose control over initiation and termination of spontaneous meals, and it is proposed that degrees of hunger and satiety determine probabilities of feeding starting and stopping. Voluntary regulation of food intake can be considered in terms of adjustments in mean meal size, meal frequency or both. Short-term variation is associated more with meal frequency and longer-term changes more with meal size. Short-term adjustments appear to depend more on alimentary control and longer-term adjustments more on metabolic control (not considered here). Long-term changes affecting meal size are associated with changes in capacity of parts of the alimentary tract. Food can accumulate in the crop and gizzard, and meal initiation and termination are associated with varying degrees of emptying and filling of these diverticula during most of the day. Later in the day there is usually a conditioned change to cumulative filling of the crop (and gizzard) with food that is digested overnight. Possible roles of osmo-/chemoreceptors and gut peptides are discussed.