Date of Graduation

5-2015

Document Type

Thesis

Degree Name

Master of Science in Poultry Science (MS)

Degree Level

Graduate

Department

Poultry Science

Advisor/Mentor

Hargis, Billy M.

Committee Member

Tellez, Guillermo

Second Committee Member

Bielke, Lisa R.

Third Committee Member

Bowen Faulkner, Olivia

Keywords

Broilers; Fluoroscein isothiocyanate dextran; Gut leakage; Intestinal inflammation

Abstract

Traditionally, antibiotic growth promoters (AGP) have been used in food animals to reduce enteric inflammation and maintain intestinal homeostasis, thus improving performance. Due to increasing restrictions regarding the use of AGP, precise and high throughput enteric inflammation models and markers to search for effective alternatives are urgently needed. Oral administration of fluorescein isothiocyanate dextran (FITC-d) and its passage into blood can be used as a marker for tight junction permeability. FITC-d is a large molecule (3-5 kDa) which does not usually leak through the intact gastrointestinal tract barrier. However, when conditions disrupt the tight junctions between epithelial cells, the FITC-d molecule can enter circulation as demonstrated by an increase in trans-mucosal permeability associated with chemically induced disruption of tight junctions by elevated serum levels of FITC-d after oral administration. In chapter one, we evaluated the dose titration of FITC-d for optimal measurement of enteric inflammation in broiler chicks using the following models: a) 24h feed restriction (FR); b) dextran sodium sulfate (DSS); or c) rye-based diet (RBD). In these experiments, FR, DSS, and RBD significantly increased (P < 0.05) serum concentrations of FITC-d, suggesting that FITC-d may be a good indicator of permeability as has been shown in some mammalian models. In chapter two, a series of experiments were conducted to evaluate the effect of dexamethasone (DEX) treatment in feed on systemic (serum) FITC-d levels, total numbers of aerobic bacteria in liver as an index of bacterial translocation (BT), differential white blood cell counts, and immune organs in broiler chickens. DEX-treated chickens showed a significant increase in serum FITC-d and BT, again indicating that stress increased paracellular leakage across the gut epithelium associated with dissolution of tight junctions. Additionally, heterophil/lymphocyte ratio was significantly increased and relative spleen and bursa of Fabricious weight ratios were significantly decreased in DEX-treated chicks. These results provide a robust measurement model for enteric inflammation model in broiler chickens to further evaluate candidate non-antibiotic anti-inflammatory treatments as candidate AGPs.

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