Evaluation of changes in serum chemistry in association with feed withdrawal or high dose oral gavage with dextran sodium sulfate- (DSS-) induced gut leakage in broiler chickens.

Dextran sodium sulfate ( DSS: ) has been shown to be effective at inducing enteric inflammation in broiler chickens, resulting in increased leakage of orally administered fluorescein isothiocyanate dextran to circulation. In a previous study, 2 doses of DSS (0.45 g/dose) administered as oral gavage resulted in increased mucosal permeability. The main objective of the present study was to compare serum turbidity in control and DSS treated birds plus with feed restriction ( FR: ), and evaluate the associated serum chemistry. Three independent experiments were conducted with different combinations of treatment groups. In Experiment 1, control full-fed ( CON: ) and DSS full-fed ( FFD: ) with n = 15 birds/group were evaluated, Experiment 2 had groups (n = 15/group) CON, FFD, feed restriction ( FRS: for 34 h), and DSS with feed restriction ( FRD: ), and Experiment 3 (n = 15/group) had CON, FFD, and FRS (29 h FRS). All DSS treated birds received one or 2 doses of DSS by oral gavage (0.45 g/dose/bird). Results showed that, compared to CON group, there was an increase (P < 0.05) in serum turbidity in FFD birds, even though the difference between FRS and FRD was not apparent (P > 0.05). Administration of DSS did not result in increase of serum enzymes such as alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase ( LDH: ), nonetheless, the FFD showed lower (P < 0.05) LDH level compared to CON in Experiment 2. Among the various serum chemistry parameters evaluated triglycerides had the highest positive correlation (r2 = 0.85; P < 0.05) with serum turbidity. DSS administration resulted in decreased serum protein levels, especially albumin. These results suggest that oral gavage with DSS in broiler chicks could result in changes to serum chemistry parameters which could be developed as potential marker/s for gut leakage.

Effect of dexamethasone in feed on intestinal permeability, differential white blood cell counts, and immune organs in broiler chicks.

We have previously shown that intestinal barrier function can be adversely affected by poorly digested diets or feed restriction, resulting in increased intestinal inflammation-associated permeability. Three experiments were conducted in broilers to evaluate the effect of dexamethasone (DEX) treatment on systemic fluorescein isothiocyanate-dextran (FITC-D; 3-5 kDa) levels, indicative of increased gut epithelial leakage. Experiment 1 compared DEX injections of 1 mg/kg, once per day on d 3, 5, and 9, with feed administration at 0.57, 1.7, or 5.1 ppm d 4 to 10, with FITC-D serum concentrations 2.5 h after gavage with 4.16 mg/kg FITC-D. All DEX treatments resulted in marked (2 to 6X; P<0.05) increased serum FITC-D levels. Feed DEX administration resulted in greater (P<0.05) gut permeability than injection at any dose, with numerically optimal effects at the lowest dose tested. In experiments 2 and 3, chicks were randomly assigned to a starter ration containing either control (CON) or DEX treated feed (0.57 ppm/kg; d 3 to 10 experiment 2, d 4 to 10 experiment 3). At d 10, all chicks were treated by oral gavage with FITC-D and serum samples were obtained as described above. Samples of the liver were aseptically collected, homogenized, diluted 1:4 wt/vol in sterile saline, and serial dilutions were plated on tryptic soy agar to evaluate total numbers of aerobic bacteria in the liver as an index of bacterial translocation (BT). In both experiments, FITC-D absorption was significantly enhanced (P<0.05) in DEX-treated chicks, again indicating increased paracellular leakage across the gut epithelium associated with dissolution of tight junctions. Experiment 2 differential cell counts showed an increased heterophil/lymphocyte ratio, and immune organ (spleen and bursa of Fabricius) weights for experiments 2 and 3 were decreased (P<0.05) from controls. In experiments 2 and 3, dietary DEX administration resulted in numerically (experiment 2) or significantly (P<0.05) increased enteric BT to the liver, supporting the observation that dietary DEX causes a stress-like inflammatory GI response, which may contribute to subclinical or clinical disease, and may be a useful model for ongoing disease mitigation research related to stress-related diseases of GIT origin.

Poultry enteric inflammation model with dextran sodium sulfate mediated chemical induction and feed restriction in broilers.

Gut inflammation is a cardinal event occurring in various gastrointestinal diseases regardless of etiology. A potential mechanism of action for antibiotic growth promoters and probiotics is alleviation or attenuation of such inflammation. In vivo inflammation models and markers to quantify changes in inflammation, such as paracellular leakage and tight junction function, are necessary tools in the search for methods to reduce enteric inflammation. Dextran sodium sulfate (DSS) and feed restriction (FRS), and fluorescein isothiocyanate dextran (FITC-d; 3 to 5 kDa) marker were evaluated for induction and assessment of enteric inflammation in broilers. Three independent experiments were conducted where birds received an inflammation inducer treatment and an oral gavage of FITC-d (2.2 mg/bird) 2.5 h before killing on d 4, followed by measurement of serum FITC-d levels and release of FITC-d from different regions of gastrointestinal tract (GIT) to evaluate tight junction function. Experiment 1 tested control (CON) and DSS; Experiments 2 and 3 evaluated CON, DSS, and FRS. In all experiments DSS, as well as FRS in Experiments 2 and 3, showed higher (P<0.05) leakage of FITC-d into serum than CON, but FRS was not different from DSS. The amount of FITC-d retained in duodenal and cecal tissue was affected (P<0.05) by FRS in Experiments 2 and 3, and DSS affected FITC-d retention in duodenum only, suggesting differences in gut passage or absorption/adsorption. In conclusion, DSS oral gavage and FRS could induce leaky gut, with changes in serum FITC-d and migration of FITC-d from GIT.

Dose titration of FITC-D for optimal measurement of enteric inflammation in broiler chicks.

Traditionally, antibiotic growth promoters (AGP) have been used in foodstock animals to reduce enteric inflammation and maintain intestinal homeostasis, thus improving growth and performance. Due to increasing restrictions regarding the use of AGP however, precise and high throughput enteric inflammation models and markers to search for effective alternatives are urgently needed. In this paper, oral administration of fluorescein isothiocyanate dextran (FITC-d, 3-5 kDa) and its passage into blood was used as a marker for tight junction permeability. In experiement 1, broilers were assigned to a control group, a group which received 24 h feed restriction (FR), or a group which received dextran sodium sulfate (DSS) (0.75% in water for 5 d), and each group then underwent an oral gavage of FITC-d 2.5 h before sample collection on d10. FITC-d in serum and intestinal samples (duodenum and ceca) were found to be higher (P<0.05) after FR than in the DSS and control groups. In experiment 2, FR was evaluated for its effect on mucosal leakage and an oral dose of FITC-d of 0.5, 1.1, or 2.2 mg/chick was used to measure the gastrointestinal tract (GIT) permeability at 6 d of age. The amount of FITC-d remaining in the duodenal tissue of the control birds increased with dose, only the 1.1 mg FITC-d/chick dose resulted in differences (P<0.05) between the control and FR groups. No differences were noted between the control and FR groups, regardless of FITC-d dosage in cecal recovery of FITC-d. Additionally, FR increased FITC-d serum levels when compared to the control group and in a dose-dependent manner. Experiment 3 compared serum levels after administration of 0.55 and 1.1 mg/chick doses of FITC-d in birds treated with FR, rye-based diet (RBD), and DSS. Intestinal sections were collected for FITC-d recovery in the 1.1 mg dosage group. All inflammation treatments significantly increased serum FITC-d levels at both doses. Only FR resulted in increased (P<0.05) FITC-d recovery from duodenum, ileum, and ceca. In conclusion, FR, DSS, and RBD affected GIT tight junction integrity, suggesting their value for enteric inflammation models, and FITC-d may be a good indicator of permeability.

Histopathological and morphometric changes induced by a dextran sodium sulfate (DSS) model in broilers.

Oral administration of dextran sodium sulfate (DSS) is commonly used as an inducer of enteric inflammation in rodents. However, there is a dearth of knowledge regarding appropriate dosage, timing, or ageresponses in broilers for this potential inducer of inflammation without necrosis. Two experiments were conducted in day-of-hatch chicks to analyze clinical parameters and enteric histological changes induced by DSS when administered via drinking water ( DW: ). In both experiments, birds were distributed into nontreated control or varying concentrations of DSS in DW. For both experiments, only 0.75% DSS in DW was histologically evaluated. In Experiment 1, chicks received DSS from day 3 to 11, and at 3, 6, and 8 d of treatment, chicks were weighed, and sections of the duodenum, ileum, and ceca were formalin fixed. The addition of 0.75% DSS caused depression, anemia, and watery bloody diarrhea, plus significantly (P < 0.05) decreased BW gain at all times. Shortened ileal villi at 6 d and duodenal villi at 8 d of treatment, reduced duodenal and ileal epithelial cell height at 3, 6, and 8 d, and increased duodenal goblet cell density at 6 and 8 d were observed in response to DSS administration (P < 0.05). In Experiment 2, birds received DSS from days 10 to 16 and were sampled at 3 and 6 d of treatment. Similar changes were found in ceca of treated birds. There was no significant change in the duodenal villus height and goblet cell density by 6 d of treatment, suggesting that 6 d of 0.75% DSS in DW was not sufficient for the reproduction of duodenal symptoms in these older birds. However, there was a significant decrease in ilealvillus height and decreased ileal epithelial cell height at 3 and 6 d of treatment, as well as a significant decrease in BW compared to the control group. These findings indicate that DW administration of 0.75% DSS caused generalized mild and non-necrotic enteritis in broilers and that this compound may be useful for enteric inflammation modeling in poultry.