The effect of fasting at different ages on growth and tissue dynamics in the small intestine of the young chick

The small intestines of hatching chicks undergo rapid developmental changes in the immediate post-hatch period when the birds are making the transitio n from endogenous nutrient supply from yolk to dependence on exogenous feed . This transition usually only begins 48 h or more after hatching, owing to logistical considerations of production. The effects of fasting for 48 h a t different times during this critical period on small intestinal developme nt and enterocyte dynamics were examined by morphometric determinations and use of staining for proliferative-cell nuclear antigen and 5-bromo-2-deoxy uridine. The effects of fasting were specific to both time of fasting and t he intestinal segment examined. Decreased development was found in the duod enum and jejunum, but was less apparent in the ileum. Fasting between 0 and 48 h decreased crypt size in the duodenum and jejunum, the number of crypt s per villus, crypt proliferation, villus area and the rate of enterocyte m igration. Fasting at later times resulted in smaller effects, although the jejunum appeared to be the most sensitive of the intestinal segments. Growt h was correlated with the number of cells in the crypts, the number of cell s along the villus and the segment surface area. The common practice whereb y feed is first available to chicks more than 48 h post-hatch may depress s ubsequent development.