The Effects Of High Fluorine On Intestinal Antioxidant Function, Immunity And Microflora In Broilers

A total of 280 one-day-old healthy avian broilers were randomly divided into four groups and fed on control diet (F 22.6 mg/kg) or the same control diet supplemented with 400,800 and 1200 mg F/kg (high F groups I, II and III) in the form of sodium fluoride for 42 days. The histopathology, biochemistry, ELISA and PCR-DGGE methods were used to investigate the effects of dietary high fluorine on intestinal antioxidant function, mucosal immunity and microflora in broilers in the present study. Results were shown below:①he length, weight and viscera index of the intestines (duodenum, jejunum and ileum) were significantly decreased (P<0.05. or P<0.01) in the high fluorine groups II and III at 42 days of age in comparison with that of the control group. Histopathologically, the intestines showed the same or similar histological alterations such as the shedding of the epithelial cells and the congestion of the intestinal villi, and the villus height, crypt depth, villus height to crypt depth ratio, diameter, muscle layer thickness as well as the numbers of goblet cells were reduced (P<0.05 or P<0.01), whereas the diameter to villus height ratio was increased (P<0.05 or P<0.01) in the high fluorine groups II and III when compared with that of the control group. Ultrastructurally, the microvilli were short and disorganized, the mitochondrial cristae were fractured and/or disappeared, the endoplasmic reticulums were dilated and the numbers of secondary lysosomes were increased in the intestines of the high fluorine groups I, II and III.② The activities of SOD, GSH-Px and CAT, GSH contents, and ability to inhibit hydroxyl radical were markedly reduced (P<0.05 or P<0.01), while the MDA level was significantly increased (P<0.05 or P<0.01) in the intestinal mucosa of the high F groups II and III.③The levels of IL-2, IL-4, IL-6, IFN-y and TNF-a were assayed by ELISA, and the experimental data showed that contents of these cytokines in the intestinal mucosa were significantly lower (P<0.05 or P<0.01) in the high fluorine groups II and III than those in the control group.④The results of Immunohistochemistry and ELISA detection showed that the numbers of IgA+cells as well as the IgA, IgG and IgM contents were markedly reduced (P<0.05 or P<0.01) in the high fluorine groups II and III in comparison with those of the control group.⑤The counts of Lactobacillus spp. and Bifidobacterium spp. in the digesta of intestines (ileum and caecum) were significantly reduced, while the counts of Escherichia coli and Enterococcus spp. were markedly increased in the high fluorine groups II and III from 21 to 42 days of age. Meanwhile, the diversity (the number of DGGE bands, similarity and Shannon index) and composition of the intestinal microflora in the high fluorine groups II and III changed greatly when compared with the control group, as revealed by PCR-DGGE.In conclusion:①Dietary fluorine in the range of 800-1200 mg/kg could decrease the villus height, crypt depth, villus height to crypt depth ratio, diameter, muscle layer thickness and goblet cell numbers, and increase the intestinal diameter to villus height ratio, implying that the intestinal development was suppressed.②Dietary fluorine in the range of 800-1200 mg/kg could decrease the activities of SOD, CAT and GSH-Px, the contents of GSH as well as the ability to inhibit hydroxyl radical formation, and increase the level of MDA, thereby causing oxidative damage of the intestinal mucosa.③Dietary high F, especially in excess of 800 mg/kg, could decrease the contents of IL-2, IL-4, IL-6, TNF-a and IFN-y, which finally impairs the function of intestinal mucosal immunity. ④Dietary fluorine in the range of 800-1200 mg/kg could reduce the number of IgA+cells and the contents of IgA, IgG and IgM, which may eventually impact the mucosal humoral immune function in the intestines of broiler. ⑤Dietary fluorine in the range of 800-1200 mg/kg obviously altered the bacterial counts (Lactobacillus spp., Bifidobacterium spp., Escherichia coli and Enterococcus spp.), diversity and composition of the intestinal microflora, implying that the initial balance of the intestinal microflora was disrupted, and this imbalance may eventually impact the health of intestines through its adversely effects on intestinal immune function and integrity.