Review on Chicken Intestinal Villus Histological Alterations Related with Intestinal Function

The normal bacterial flora contains antibiotic resistance genes to various degrees, even in individuals with no history of exposure to commercially prepared antibiotics. Several factors seem to increase the number of antibiotic-resistant bacteria in feces. One important factor is the exposure of the intestinal flora to antibacterial drugs. Antibiotics used as feed additives seem to play an important role in the development of antibiotic resistance in normal flora bacteria. The use of avoparcin as a feed additive has demonstrated that an antibiotic considered "safe" is responsible for increased levels of antibiotic resistance in the normal flora enterococci of animals fed with avoparcin and possibly in humans consuming products from these animals. However, other factors like stress from temperature, crowding, and management also seem to contribute to the occurrence of antibiotic resistance in normal flora bacteria. The normal flora of animals has been studied with respect to the development of antibiotic resistance over four decades, but there are few studies with the intestinal flora as the main focus. The results of earlier studies are valuable when focused against the recent understanding of mobile genetics responsible for bacterial antibiotic resistance. New studies should be undertaken to assess whether the development of antibiotic resistance in the normal flora is directly linked to the dramatic increase in antibiotic resistance of bacterial pathogens. Bacteria of the normal flora, often disregarded scientifically, should be studied with the intention of using them as active protection against infectious diseases and thereby contributing to the overall reduction of use of antibioties in both animals and humans.

An experiment was conducted to test the hypothesis that the decline in eggshell quality over time during egg production, and its improvement after molting, paralleled the rate of calcium uptake by the duodenum of the laying hen. In vitro duodenal calcium uptake rate and femur ash (percentage of femur weight) were determined at 37, 45, 51, 58, 68, and 72 wk of age. Percentage shell and shell thickness (millimeters) were determined at 22, 29, 36, 44, 50, 57, and 71 wk of age. Molt was induced at 63 wk of age. Three commercial strains DeKalb XL-Link, ISA/Babcock B-300V, and Hy-Line W-36 were compared. There were no differences in duodenal calcium uptake rate among strains. There was a significant decline (P < .01) in duodenal calcium uptake from 408 pmol/mg tissue per min at 37 wk of age to 329 pmol/mg per min at 58 wk of age. Femur ash decreased (P < .01) from 50.8% at 37 wk of age to 47.6% at 58 wk of age. Percentage shell and shell thickness declined (P < .01) from 9.79% and .403 mm at 22 wk of age to 8.88% and .373 mm at 57 wk of age, respectively. After the induced molt, duodenal calcium uptake increased (P < .01) to 402 pmol/mg tissue per min, and percentage shell and shell thickness increased (P < .01) to 10.23% and .389 mm, respectively. Duodenal calcium uptake increased immediately postmolt, whereas femur ash did not increase until 72 wk of age (P < .01).

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.