DEVELOPMENT OF THE SMALL-INTESTINE IN HEAVY AND LIGHT STRAIN CHICKS BEFORE AND AFTER HATCHING

1. Intestinal development was examined in Arbor Acres and Lohmann chic ks from one week before hatching until one week after. Changes in morp hology and concentrations of DNA, RNA and protein in the duodenal tiss ue were determined. 2. Villus height and perimeter increased 9 to 11 f old from day 14 of incubation until 7 d after hatching. Arbor Acres ch icks had values which were consistently higher than Lohmann chicks. 3. DNA concentration of duodenal tissue increased with age in parallel t o the increase in the number of enterocytes per villus. In the pre-hat ch period tissue activity as indicated by RNA/DNA, and ribosomal capac ity as shown by the RNA/protein ratios, were high for both strains; va lues for Arbor Acres embryos and chicks were greater than for Lohmann. 4. DNA concentrations, RNA/DNA, RNA/protein and protein/DNA ratios co rrelate with morphological measurements and can be used as additional criteria for evaluating development in chick intestine. 5. In the last week of incubation and immediately after hatching, intestinal growth appears to arise mainly from cellular hyperplasia and not from cellula r hypertrophy. Intestinal development patterns were similar for both s trains but growth was more rapid in Arbor Acres chicks.