Fecal Transplant for Treating Diarrhea in Adult Horses 

Researchers evaluated the efficacy of fecal transplants in equine enterocolitis cases.
Sick horse with diarrhea in stall
Clinical parameters of horses receiving FMT did not improve compared to control horses in this study. | Getty Images

Many treatments are available to address complicated diarrhea or colitis in horses. One of these treatments is fecal microbiota transplant (FMT), also called transfaunation. Equine practitioners from UC Davis, Hagyard Equine Medical Institute, and Steinbeck Peninsula Equine Clinics participated in a retrospective study to evaluate the efficacy of fecal transplants in enterocolitis cases.  

Fecal Microbiota Transplant (FMT) Study

The technique involves feces collected from a healthy equine donor. After straining the material, the veterinarian administers fecal fluid to a recipient horse via nasogastric tube. The study authors reviewed the effects of fecal transplant in 37 horses older than 1 year that were hospitalized for treatment of diarrhea. They compared this group to 74 control horses treated with conventional methods and hospitalized at the same time in the same hospital—either UC Davis Veterinary Medical Teaching Hospital or Hagyard Equine Medical Institute. All horses received a proton pump inhibitor (omeprazole) prior to FMT treatment to decrease gastric acidity. Lowering gastric acidity has the potential to improve bacterial survival as the fecal fluid transits through the stomach environment to the large intestines. 

Veterinarians implemented FMT on Day 6 of hospitalization in most cases. They treated the horses with FMT between one and five times, with a median of two treatments. At the first equine practice, veterinarians mixed 3 liters of fecal fluid with 1-3 liters of bismuth subsalicylate. Of 24 horses receiving FMT, 18 also received antimicrobials. At the other equine practice, 13 horses received 2-5 liters of fecal fluid. Eight of the 13 received only fecal fluid, and the other five also received either bismuth subsalicylate or a feed supplement digestive fortifier or Bio-Sponge. Of the 13, eight received systemic antimicrobial agents. 

Study Results

The horses in the control group had shorter hospitalizations (seven days median) than those treated with FMT (12 days median). Fecal consistency improved in a median of 7.5 days in controls and 11 days in FMT horses. Control horses’ attitudes also improved quicker than those receiving transfaunation. The authors proposed this result could be somewhat biased because the horses given FMT might have had a more serious diarrhea condition that failed to resolve with conventional treatment.  

Study Conclusions

The authors concluded from this retrospective study that clinical parameters of horses receiving FMT did not improve compared to control horses. The findings also suggest antimicrobial drugs should be discontinued prior to transfaunation in horses with diarrhea. More research is recommended to focus on intestinal microbiota composition of donors as well as on efforts to optimize microbial survival within the fecal fluid once it enters the recipient’s stomach. 


Quattrini C, Bozorgmanesh R, Egli P, Magdesian KG. Fecal microbiota transplant for treatment of diarrhea in adult hospitalized horses – 111 cases (2013 – 2018). Open Access Veterinary Journal 2023, vol. 13(9): 1135 – 1140; DOI: 10/5455/OVJ.2023.v13.i0.9

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