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ARS Home » Midwest Area » Lexington, Kentucky » Forage-animal Production Research » Research » Publications at this Location » Publication #407565

Research Project: Sustainable Forage Production Systems for the Mid-South Transition Zone

Location: Forage-animal Production Research

Title: Equine fecal microbiota response to short term antibiotic administration

item PARKER, JORDAN - University Of Kentucky
item PAGE, ALLEN - University Of Kentucky
item JACOB, OLIVIA - University Of Kentucky
item STANTON, TORI - University Of Kentucky
item Harlow, Brittany
item Flythe, Michael
item ADAM, EMMA - University Of Kentucky

Submitted to: Journal of Equine Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/30/2023
Publication Date: 1/1/2024
Citation: Parker, J.L., Page, A., Jacob, O., Stanton, T., Davis, B.E., Flythe, M.D., Adam, E.N. 2024. Equine fecal microbiota response to short term antibiotic administration. Journal of Equine Veterinary Science. 133.

Interpretive Summary: Horses are prescribed antibiotics for a variety of bacterial infections. Unfortunately, some horses that receive antibiotics develop diarrhea. Antibiotic associated diarrhea (AAD) can be mild or serious, even life-threating. The spectra of activities of veterinary antibiotics include a wide range of bacteria, including the beneficial bacteria that live in the gastrointestinal tract of the animal. It is thought that when antibiotics kill beneficial bacteria, the gut can be colonized by pathogenic bacteria that cause AAD. Healthy horses were treated with one of three typical antibiotic therapies. Several groups of normal and beneficial bacterial were monitored in the feces of the horses for 28 days. Individual horses responded differently, but in general beneficial bacteria decreased. There was a simultaneous appearance of two pathogens that are known to cause diarrhea. These results support the idea that horses become vulnerable to pathogenic bacteria when their normal bacteria are suppressed.

Technical Abstract: Though generally deemed safe, research continues to demonstrate negative side effects of antibiotic administration on the gastrointestinal (GIT) microbiota across species. In horses, antibiotic associated diarrhea (AAD) is a life-threatening condition linked to the GIT microbiota. This study tested the hypothesis that short term antibiotic administration to healthy horses would negatively impact the fecal microbiota as measured by their ability to digest nutrients and through fecal shedding of disease-associated-bacteria. Twenty-four horses were assigned to one of four treatment groups: control (CO); potassium penicillin/gentamicin sulfate (KPG); ceftiofur crystalline free acid (EX); trimethoprim/sulfamethoxazole (SMZ); and treated for 4 days. Fecal samples were collected before treatment began (S0), the day after treatment conclusion (S5), and at 10, 14, 21, and 28 days after initiating treatment. Horses had highly individualized responses to antibiotic administration. All horses receiving antibiotics experienced significantly softer stool compared to controls. Lactobacillus spp. were dramatically reduced in all antibiotic treated S5 samples. Horses receiving antibiotics were significantly more likely to test positive for C. difficile or C. perfringens on fecal qPCR. In conclusion, response to antibiotic administration displays high inter-individual variability, but shows changes to the functions of fecal microbiota that may depend on the antibiotic used.