Abstract
Background:
Fecal microbiota transplant (FMT) is increasingly administered as part of the treatment of colitis in horses, yet there are little data as to effectiveness.
Aim:
Retrospective evaluation of the effects of FMT on discharge status, fecal consistency, length of hospitalization and improvement in clinical signs in horses hospitalized for diarrhea.
Methods:
Retrospective case-control study. Medical records of adult horses (>1 year old) that received at least one transfaunation treatment (2013-2018) in two referral hospitals were identified through a medical records database search. Medical records of contemporary adult horses with diarrhea that did not receive FMT at the same study centers were used as controls.
Results:
Control horses had statistically significant shorter hospitalization (7 [1-21]) as compared to the transfaunation group (12 [3-31]) (P=0.0006). There were no significant differences between groups in number of days to improvement of feces (P=0.38), or in days to normalization of fecal consistency (P=0.43), respiratory rate (P=0.42), heart rate (P=0.27), body temperature (P=0.12), peripheral white blood cell count (P=0.37), improvement in appetite (P=0.81) or attitude (P=0.06). There was also no significant difference in survival to discharge (transfaunation 28/37, 75.7%; control 56/74, 75.7%, P=1.0).
Conclusions:
There were no significant advantages of performing fecal microbiota transplant in horses with diarrhea in this retrospective study. This highlights the need for prospective, randomized studies to evaluate the efficacy of FMT, as well as different formulations, in horses with colitis before this can become standard practice.

Key words: Colitis, Diarrhea, Equine, Transfaunation, Treatment