Antibiotics are important to equine medicine, but can cause detrimental side-effects including reduced feed intake, allergic reactions, and diarrhea. Antibiotic-associated diarrhea (AAD) is attributed to disruption of the hindgut microflora, permitting proliferation of pathogenic microbes. The objectives were to evaluate the effects of antibiotics on beneficial fecal bacteria, AAD-associated pathogens, microbial species richness and fermentation. Horses were assigned to treatment groups: control (no antibiotics, n=6), trimethoprim-sulfadiazine (oral, n=6), or sodium ceftiofur (IM, n=6). Fecal samples were taken during adaptation (3 wk), antibiotic challenge (1 wk), and withdrawal (1 wk). Fecal cellulolytics decreased by >99% during challenge and did not recover during withdrawal (P < 0.0001). Lactobacilli decreased by >60% during challenge (P = 0.0453). Salmonella spp. increased 94% with trimethoprim-sulfadiazine challenge (P = 0.0115). There was no detectable Clostridium difficile during adaptation or in any control horse. C. difficile increased (P < 0.0001) when horses were challenged, and remained elevated 7 d after withdrawal. There was no effect of challenge on in vitro digestibility or microbial species richness as evaluated by denaturing gradient gel electrophoresis (P > 0.05). These results indicate that antibiotics can disrupt the normal flora and allow proliferation of pathogens, even without affecting digestibility and causing AAD.
| Identifer | oai:union.ndltd.org:uky.edu/oai:uknowledge.uky.edu:animalsci_etds-1011 |
| Date | 01 January 2012 |
| Creators | Harlow, Brittany E |
| Publisher | UKnowledge |
| Source Sets | University of Kentucky |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations--Animal and Food Sciences |
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