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1. The fine structural alterations of villi and epithelial cells in each part of the small intestine were investigated in layer-type hens fasted for 12 h to 20 d or refed for one day after each fasting period. 2. Within the first 24-h-fasting, villi of the duodenum showed a remarkable reduction in height and those of the jejunum revealed a gradual decrease; such a significant reduction of the villus height was not obtained in the ileum. After 36-h-fasting, villus height in each part gradually decreased with days of fasting. 3. All intestinal villus heights increased after only 1-d-refeeding of various kinds of diets following 3-, 10-, or 20-d-fasting. The duodenum especially rapidly recovered even after long-term fasting of 20 d but the ileum showed very slow recovery, suggesting that the ileum seems to be inactive in absorptive function. 4. These variable alterations of villus height in the proximal intestine suggest that the higher intestinal absorptive ability is under the normal feeding, the more rapidly villus height is influenced by nutritional conditions. 5. Cell area and cell mitosis decreased after fasting, the latter showing a marked reduction. However, in spite of a remarkable decrease of cell mitosis in the proximal intestine after fasting, refeeding activated cell renewal and it soon reached control levels, demonstrating that the villus height mainly varied with the numbers of epithelial cells. 6. In the epithelial cells of the proximal intestine in chickens fasted for 20 d, large lysosomal autophagous vacuoles including mitochondria and dense bodies were observed. These were reduced in size by refeeding for only one day, suggesting that fasting may cause intracellular digestion through lysosomal autophagy. 7. These results lead to the conclusion that long-term for force moulting is possible, that a high protein and high energy diet can be fed immediately after fasting and that a cell undergoing lysosomal autophagy in normal chickens indicates undernutrition.

Recovery responses of intestinal villus height and fine structure on the villus apical surface to different refeeding procedures were compared at refeeding 3 or 24 h after 3-d of feed withdrawal from chicks. After 3-d of fasting, 45-d-old male White Leghorn chicks (Gallus gallus domesticus) were refed rice bran (RB) (CP, 14.8%; ME, 3,170 kcal/kg), conventional grower mash diet (CG) (CP, 18.2%; ME, 2,853 kcal/kg), or ground CG (GG). During the experimental period, birds were given access to diets and water ad libitum. After the end of each experimental period, the duodenum was fixed and examined by light and scanning electron microscopy for morphological changes in the villi. Duodenal villus heights of chicks fasted for 3 d were significantly decreased compared with control chicks fed ad libitum. Villus heights were significantly increased after a 3-h refeeding, and the villi of the GG-refed group were significantly higher than RB and CG. When compared with villus heights at the 3-h refeeding, the RB-refed group showed no changes after a 24-h refeeding, but the CG and GG groups had significantly increased villi heights. Villi heights in GG groups were significantly higher than in the CG groups. Dietary effects on cell area and cell mitosis numbers were similar to those observed for villus height. The surface of the duodenal villi apices of control birds fed ad libitum revealed a clear cell outline, cell protuberances, and cell extrusion into the lumen. After 3-d fasting, cell outlines became faint, and protuberances and extrusion of cells disappeared. After refeeding for 3 h, clear cell outlines were again apparent in all groups. In GG-refed chicks, larger cell outlines and protuberated cells were found as conspicuous morphological features. Similar observations were made at the 24-h refeeding. These morphological findings suggest that chickens that were on feed withdrawal benefit from ad libitum refeeding of a powdered diet that is nutritionally complete for rapid recovery of digestive function.

1. To obtain intestinal morphological data demonstrating the faster growth rate in broiler (BR) than in White Leghorn (WL) chickens, villi of the duodenum, jejunum and ileum were examined from 1 to 30 d of age by scanning electron microscopy. 2. At the first day after hatching, villi of each intestinal segment showed a finger-like shape in both breeds. Villi developed to a plate-like shape in the duodenum, a wave-like shape in the jejunum and a tongue-like shape in the ileum at 30 d of age via the common plate-like villi at 10 d of age. The fundamental villous shape and arrangement seem to be accomplished by 10 d of age; two types of obliquely elongated plate-like villi showed a zigzag arrangement, adjoining at an angle of 40 degrees to 60 degrees like an oblique T-shape. It is suggested that such a villous arrangement would be more effective for nutrient absorption by inducing a long zigzag flow of ingesta. 3. Compared with WL, even at the first day after hatching BR had many more developed epithelial cell protrusions over the whole apical surface of the duodenal villi. In WL the protrusions were not so apparent and located only in the central area of the villous tip. Furthermore, at 10 d of age BR showed more developed and larger villi, many wider microvilli at the apical portion of villi and more active extrusions of epithelial cells from the tip of the duodenal and jejunal villi. 4. These morphological characteristics of villi in early life in BR suggest a greater absorptive surface area and a more active intestinal function, permitting the faster growth rate of BR immediately after hatching.

To establish the intestinal histological alterations in chickens fed low-crude protein (CP) or low-crude fat (EE) in long-term isocaloric diets, 60 birds were allotted to three treatments, each with five replicates of four chickens. They were fed the control, low-CP or low-EE diet from the age of 9 to 16 weeks. The chickens receiving the low-CP diet showed a clear reduction in performance and carcass characteristics like breast and wings. However, these adverse effects did not occur in the chickens fed the low-EE diet. The villus height in the duodenum and ileum were lower (P<0.05) in the low-CP group. The duodenal villus area decreased (P<0.05) in both the low-CP and low-EE groups, whereas the ileum showed a lower value (P<0.05) in only the low-CP group. The cell area of the duodenum and jejunum displayed decreasing values (P<0.05) in the low-CP and low-EE groups. As regards the mitotic numbers, the jejunum and ileum showed a decrease (P<0.05) in the low-CP group. On the villus tip surface in the duodenum of the control and low-EE groups, clear protuberant cells and cell clusters with a great number of epithelial cells were found. These cell clusters degraded to faintly dome-shaped cells in the low-CP group, resulting in a lower level of morphological changes than in the other two groups. The epithelial cells on the jejunal and ileal tip surfaces did not show a specific change in the treatment groups. This work is licensed under a Creative Commons Attribution 3.0 License (by-nc 3.0). ©Copyright T.