Hatching birds which have been dependent on the yolk for their energy supply during much of the embryonic period must undergo a rapid transition to utilising carbohydrate rich exogenous feed. This change is accompanied by the preferential growth of the small intestine and activation of digestive enzymes and absorption pathways. The ontogeny of these processes is described and includes the intense development immediately after hatching. The effect of delayed access to feed on intestinal development is also discussed.
