This study was conducted to investigate how chitosan (COS) affects intestinal mucosal barrier function and to further explain mechanisms of COS on growth performance. Thirty piglets, weaned at 21 days of age, were challenged with enterotoxigenic Escherichia coli during preliminary trial period. Three groups of Piglets in individual pens were fed a corn-soybean meal diet containing no addition, 50 mg/kg chlortetracycline, or 300 mg/kg COS for 21 days. Jejunal morphology and histology were analyzed under light microscope. The concentrations of occludin proteins were determined by western blot. Immunohistochemistry assays were used to determine secretory immunoglobulin (sIgA) level. Real-time PCR was used to detect Toll-like receptor 4 (TLR4) and Claudin-1 in jejunal mucosa. Feeding COS or chlortetracycline reduced (P<0.05) feed conversion ratio. Villus length, villus length/crypt depth, and goblet cells, were increased (P<0.05), but villus width and crypt depth were decreased (P<0.05) in both COS and chlortetracycline groups. Intraepithelial lymphocytes were higher (P<0.05) in the COS group than both chlortetracycline and control groups. Occludin protein expression was increased (P<0.01) in the COS group, but was decreased (P<0.05) in the chlortetracycline group. Expression of sIgA protein was higher (P<0.05) in the COS group than both control and chlortetracycline groups, however TLR4 mRNA expression was decreased (P<0.05) in both COS and chlortetracycline groups. There was no difference in expression of claudin-1 among the three groups. In conclusion, chitosan and the antibiotic have similar effects in promoting piglet growth and reducing intestinal inflammation, but different effects on intestinal mucosal barrier function. This indicates that chitosan can replace chlortetracycline as a feed additive for piglets.
Keywords: ABC; ADFI; ADG; ANOVA; Amino Acids; Average daily feed intake; BCA; CD; COS; Chitosan; DAB; DEPC; Digestion; ETEC; F/G; GAPDH; GCs; GLM; IECs; IELs; IL-6; Intestinal mucosal immunological barrier; NF-κB; Nutrition; OD; Occludin; PBS; Piglets; SAS; SDS PAGE; TJs; TLR4; TNF-α; Toll-like receptor 4; analysis of variance; average daily gain; avidin–biotin–peroxidase complex; bicinchoninic acid; chitosan; cluster of differentiation; diaminobenzidine; diethyl pyrocarbonate; enterotoxigenic Escherichia coli; feed conversion ratio; general linear model; glyceraldehyde-3-phosphate dehydrogenase; goblet cells; inhibiting nuclear factor kappa B; interleukin-6; intestinal epithelial cells; intraepithelial lymphocytes; optical density; phosphate buffered saline; sIgA; secretory immunoglobulin; sodium dodecyl sulfate–polyacrylamide gel electrophoresis; statistical analysis system; tight junctions; tumor necrosis factor alpha.
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