Functional development of the small intestine in domestic birds: Cellular and molecular aspects

The development of a functionally intact intestinal tract is essential for the successful production of poultry, particularly meat-type birds and turk eys, Yet, a paucity of information exists on the development of the small i ntestine, especially in newly hatched chicks and poults. Several criteria a re used by our group for examining intestinal maturation and functional dev elopment of the small intestine. Among them are morphological studies, ente rocyte proliferation, migration and turnover time, and the biochemical acti vity and RNA expression of brush-border enzymes. Our observations have docu mented rapid morphological development after hatching with differing rates of increase in villus volume in the duodenum, jejunum and ileum. When acces s to first feed is delayed, small intestinal development is slower. Prolife rating cells are located in the crypt and up to the middle region of the vi llus, with the crypt region exhibiting a significantly higher number of pro liferating cells. Different migration rates of enterocytes along the villi are observed in the three sections of the small intestine, with the highest rate in the duodenum and the lowest in the ileum. The brush-border enzyme activities differ in the three regions of the small intestine and are alter ed when first feeding is delayed or in vitamin A deficient diet. The use of cDNA probes detected the RNA expression of two brush-border enzymes. The u nderstanding of molecular mechanisms regulating enterocyte proliferation an d functional maturation will introduce a new dimension to poultry nutrition and will contribute to a better matching of the diet at an early age. More over, it will open a field of manipulations, administrated either by in-ovo treatments or in the first days after hatch, which will contribute to earl ier development of the small intestine.