Date of Graduation

5-2020

Document Type

Thesis

Degree Name

Master of Science in Poultry Science (MS)

Degree Level

Graduate

Department

Poultry Science

Advisor

Xiaolun Sun

Committee Member

Billy M. Hargis

Second Committee Member

Young Min Kwon

Keywords

Alternative to antibiotics, Bile acids, Growth promotion, Microbiology, Necrotic enteritis, Poultry health

Abstract

Necrotic enteritis (NE) has re-emerged following restriction of antimicrobial usage and costs $6 billion every year worldwide. The primary objective of the studies was to evaluate prevention and treatment of NE using a microbiota metabolic product, secondary bile acid deoxycholic acid (DCA), in drinking water. Day-old birds were tagged and placed in floor pens. In experiments 1 and 2, the birds were infected with Eimeria maxima (Em) at d 18 and C. perfringens at d 23 and 24 and the birds were euthanized at d 26. In experiment 3, birds were infected with Eimeria at d 20 and C. perfringens at d 25 and 26 and euthanized at d 27. DCA was administered in drinking water at 1.91, 0.95, or 0.48 mM, respectively. Small intestinal content and tissue were collected for histopathology and molecular study. Data were analyzed using one-way ANOVA followed by t-test. NE birds in experiment 1 developed subclinical signs of NE, while NE birds in experiment 3 suffered acute NE. DCA at 1.91 mM attenuated the BWG loss in experiments 1 and 3. Consistently, it reduced NE-induced intestinal histopathology in experiments 1 and 3. However, in experiment 2 because of minimal body weight alteration in Em and NE birds compared to non-infected birds, no tissue was collected. DCA reduced NE-induced expression of inflammatory gene Infγ in experiment 1. Similarly, DCA reduced elevation of NE-associated C. perfringens luminal colonization in experiment 1. Using targeted metabolomics (LC-MS/MS) of bile acids, we found that NE was associated with reduction of total bile acids in ileal content.

The second objective of the studies was to examine improvement of broiler chickens growth through modulating gut microbiota. Mouse specific pathogen free (SPF) stool was cultured on Brain Heart Infusion (BHI) agar under anaerobic or aerobic condition and collected as SPF anaerobic (SPF-Anaero) and aerobic (SPF-Aero) microbiota. Day-old birds were tagged, weighed and randomly assigned to 9 pens. The birds were then orally gavaged with PBS, 108 CFU/bird SPF-Anaero, or 108 CFU/bird SPF-Aero. Body weight was measured at d 0, 14, and d 28, and euthanized at d 28. Data was analyzed using one-way ANOVA followed by t-test. Birds colonized with SPF-Anaero grew 15% heavier during d 0-14 (28 vs. 24 g/day/bird, P= 0.0009) compared to control birds, while birds colonized with SPF-Aero gained 8% more body weight compared to control birds (26 vs. 24 g/day /bird, P= 0.02). Consistently, SPF-Anaero birds grew faster compared to control birds during d14-28 (67 vs. 60 g/day/bird, P= 0.007). SPF-Anaero and SPF-Aero birds grew 15 and 4%, respectively, heavier on accumulative body weight gain compared to control birds (47 vs. 42 g/day/bird, P= 0.0009; 44 vs. 42 g/day/bird, P= 0.03, respectively).

In conclusion, microbial metabolic product DCA in drinking water prevents NE-induced BWG reduction and histopathology, perhaps through reducing C. perfringens colonization and/or bile acid restoration. Modulating microbiota could be used as an antimicrobial free alternative to improve bird body weight gain. These findings may offer an alternative strategy to use of DCA and microbiota for NE prevention and growth promotion.

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