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.

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.

Efficacy of Salmonella enteritidis-immune lymphokines on horizontal transmission of S. arizonae in turkeys and S. gallinarum in chickens.

Salmonella arizonae (SA) and S. gallinarum (SG) are of economic importance to international poultry production because of their pathogenesis in young poultry during the first week after hatching. Previous studies from our laboratory have shown immune lymphokines (ILK) produced by S. enteritidis (SE)-immunized chickens provide protection against SE organ invasion in day-old chickens and turkey poults. Previous studies have also demonstrated that SG organ invasion was significantly decreased by administration of ILK to broiler chicks. The objective of the present study was to determine the effect of ILK on the incidence of horizontal transmission of SA in turkey poults and of SG in broiler chicks. The effect of ILK administration on horizontal transmission of SA in poults and SG in chicks was assessed in a seeder/contact model. Seeders were challenged with the appropriate bacterium (SA turkeys, SG chicks), contacts were either untreated or administered ILK. Seeders and contacts cohabited within an experimental group throughout the experiment. Mortality and organ invasion as a result of horizontal transmission were determined. There were no significant differences in mortality between non-treated and ILK-treated contact poults. In contrast, SG was extremely pathogenic to young broiler chicks. Non-treated contact chicks had a mortality rate of approximately 68% whereas significant (P < 0.05) reduction in mortality was demonstrated in the contact chicks treated with ILK (15%). Horizontal transmission, as determined by organ invasion, of SA to contact turkey poults and SG to contact broiler chicks was also significantly (P <0.05) decreased by immunoprophylactic administration of ILK. Bacterial recovery of SA from the liver/spleen and the cecal tonsil in contact poults and SG from contact chicks treated with ILK was dramatically reduced when compared to non-treated contact poults and chicks. Our results strongly suggest the immunoprophylactic administration of SE-immune lymphokines to young turkey poults and broiler chicks significantly reduces the horizontal transmission of Salmonella in poultry. These results suggest the possibilities of using a non-vaccine immunologically-based preventative strategy against Salmonella in poultry.

Immunoprophylaxis of Salmonella enteritidis infection by lymphokines in Leghorn chicks.

Chickens were treated prophylactically with the soluble products from Con A-stimulated T-lymphocytes from Salmonella enteritidis-infected chickens in order to investigate the effect of such prophylactic treatment on organ invasion by S. enteritidis. At 18 days of age, chicks were injected intraperitoneally with one of the following: A) the Amicon YM 10 ultrafiltrate from immunized chickens, B) the Amicon YM 10 ultraretentate material from immunized chickens, or C) the Amicon YM 10 ultraretentate material from control nonimmune chickens. Thirty minutes after lymphokine injection, all birds were challenged per os with 10(8) colony-forming units of S. enteritidis. At both 1 and 6 days post-challenge, prophylactic treatment of chickens with the immune retentate resulted in a 51-60% reduction in S. enteritidis organ invasion. The reduction in S. enteritidis organ invasion was associated with a significant increase in lamina propria thickness based on morphometric analysis (P < 0.05). These results demonstrate that the prophylactic administration of S. enteritidis-immune lymphokines induces protection against S. enteritidis organ invasion, which is associated with a measurable microanatomical change in the cecal mucosa.

Effect of prolonged administration of dietary capsaicin on Salmonella enteritidis infection in leghorn chicks.

The effect of 14 or 19 days of dietary capsaicin (18 ppm) on Salmonella enteritidis infection and histological, morphometric, and pH changes of the ceca was investigated. At day 13 or day 18, chicks were challenged with 10(8) colony-forming units of S. enteritidis. Chicks were killed and cultured 24 hours later. The total number of S. enteritidis-organ-culture-positive chicks was significantly lower among chicks fed capsaicin for either 14 or 19 days than among controls (P < 0.05). Subjective histological examination revealed a mild to moderate infiltration of mononuclear cells and heterophils in lamina propria of ceca, as well as epithelial cell proliferation in chicks following either 14 or 19 days of capsaicin administration. Using morphometric analysis, the mean lamina propria thickness and mean epithelial cell thickness in chickens fed capsaicin for 14 or 19 days were significantly greater than in controls (P < 0.05). Capsaicin significantly decreased luminal pH in both trials (P < 0.05). These data indicate that the observed capsaicin-induced resistance to S. enteritidis organ invasion is associated with measurable pH and morphological changes of the cecal mucosa.

Effect of a commercial competitive exclusion culture (Preempt) on mortality and horizontal transmission of Salmonella gallinarum in broiler chickens.

A commercial competitive exclusion (CE) culture (PREEMPT) was evaluated for its ability to decrease mortality during the first 10-12 days posthatch resulting from the causative agent of fowl typhoid, Salmonella gallinarum. In the first experiment, chicks provided the CE culture on day of hatch and challenged with 10(5) S. gallinarum on day 3 had a significant decrease in mortality compared with non-CE-treated S. gallinarum-challenged chicks in all four replicates. Mortality for control chicks when averaged across all four replicates was 74% compared with 7.5% for the CE-treated chicks. A second experiment was performed that was designed to measure the efficacy of the CE culture in decreasing the horizontal transmission of this pathogen from infected to uninfected chicks when commingled. Day-of-hatch chicks that were directly infected (seeders) with 10(5) S. gallinarum and provided no CE culture averaged 86% S. gallinarum organ positive and 80% mortality during the first 12 days posthatch across four replicates. Untreated contact (not directly infected) chicks that were commingled with the seeder chicks averaged 84% S. gallinarum organ positive and 54% mortality, and the commingled CE-treated contact chicks (provided CE culture on day of hatch) average 35% S. gallinarum organ positive and 9% mortality during the same time period. These results are of importance to the poultry industry in geographic areas where poultry production is adversely affected by fowl typhoid and indicate that treating newly hatched chicks with this commercial CE culture may be a novel way of decreasing economic losses associated with this highly pathogenic organism.

Eimeria tenella or Eimeria adenoeides: induction of morphological changes and increased resistance to Salmonella enteritidis infection in Leghorn chicks.

The effect of either low doses of the chicken coccidium, Eimeria tenella (ET) or high doses of the turkey coccidium, Eimeria adenoeides (EA) on Salmonella enteritidis (SE) organ invasion, as well as histological and morphometric changes in the ceca of Leghorn chicks, was investigated. In these studies, chicks were inoculated orally with either saline solution (control) or one of three doses of sporulated oocysts of either ET or EA at 1 d of age. Five days later, 10(4) cfu of SE were administered per os to all chickens. Chicks were killed and organs cultured for SE 6 d following bacterial challenge. A clear relationship of decreased SE organ invasion was observed by increasing the dose of sporulated oocysts of either ET or EA. Furthermore, the increased resistance to organ infectivity in both experiments was matched with an increase in lamina propria thickness based on morphometric analysis (P < .05), probably due to a marked infiltration of inflammatory cells in the cecal mucosa. In both trials, a significant correlation was found (r = -.98 for ET; r = -.99 for EA) between the rate of bacterial organ infectivity and lamina propria thickness of the cecum. These data indicate that the increased resistance to SE organ invasion following subclinical coccidial infections were associated with morphological changes in the ceca of Leghorn chicks.

Salmonella enteritidis immune leukocyte-stimulated soluble factors: effects on increased resistance to Salmonella organ invasion in day-old Leghorn chicks.

Cytokines, derived from either concanavalin A-stimulated Salmonella enteritidis-immune chicken T lymphocytes [SE-immune Lymphocyte Stimulated Soluble Factor (LSSF)] or lipopolysaccharide-stimulated SE-immune chicken macrophages [SE-immune Macrophage Stimulated Soluble Factor (MSSF)], were evaluated for their ability to increase resistance to SE organ invasion in day-old Leghorn chicks. In Trial 1, day of hatch chicks were injected i.p. with either SE-immune LSSF or SE-nonimmune LSSF (control). In Trial 2, chicks were similarly injected with either SE-immune MSSF, SE-nonimmune MSSF, or SE-immune LSSF (positive control). Thirty minutes postinjection, all chicks were gavaged with an invasive dose of SE. Twenty-four hours later, livers and spleens from all chicks were cultured for SE. In Trial 1, SE-immune LSSF caused a rapid and marked protection (P < .01) against SE infection as determined by the number of chicks that were culture positive regardless of challenge dose. In Trial 2, SE-immune MSSF was not associated with protection against SE organ infection. These experiments demonstrate that SE-immune LSSF, but not MSSF, are able to confer protection against SE organ invasion in day-old Leghorn chicks. Thus, it appears that the stimulated immune T cell, and not the macrophage, is responsible for producing the soluble products that protected the chicks.

Heterophils are decisive components in the early responses of chickens to Salmonella enteritidis infections.

Chickens injected with 5-fluorouracil (5-FU) were found to have a three- to nine-fold reduction in circulating heterophils without a reduction in the number of circulating mononuclear cells. A 50% organ invasive dose (ID50) for orally and intravenously administered Salmonella enteritidis (SE) was established in the heteropenic chickens. When challenged orally, about 150-fold fewer SE cells were required for organ invasion in the 5-FU-treated chickens; whereas an intravenous challenge of the heteropenic chickens required about 4000-fold fewer bacteria for organ invasion than found in the control birds. Significant (P < 0.0001) SE-dose-dependent reductions in body weight with increased mortality and lesions in the eye, heart, and thymus were found in the 5-FU-treated birds versus the control birds. Alternatively, the control birds had significantly more intestinal lesions than the 5-FU-treated birds. No consistent significant hepatic lesions were observed in either treatment group. Under the conditions used in these experiments, 5-FU treatment of chickens caused otherwise subclinical SE infections to rapidly become clinical infections with more severe extraintestinal organ infections, whereas the control chickens had infections that were primarily restricted to the intestine. These findings suggest that the heterophil is extremely important in controlling both initial SE organ invasion and subsequent disease pathogenesis in chickens.