In infants, defecation often follows a meal. The cause Gastroileal reflex of colonic contractions in this situation is

Gastrocolic reflex refers to the contraction of colon induced by entry of food into the stomach. This reflex results in an urge to defaecate after a meal. Because of this, defaecation after meals is a rule in children.However, in adults, the bowel training suppresses this reflex. Ref: Medical physiology, Indu Khurana