Background An association between equine gastrointestinal disease causing colic signs and changes in faecal bacterial microbiota has been identified. The reasons for these changes and their clinical relevance has not been investigated. Withholding feed, which is an integral part of managing horses with colic, may contribute to the observed changes in the microbiota and impact interpretation of findings in horses with colic. Study objectives were, therefore, to determine the effect of withholding feed for 24 h on equine faecal bacterial microbiota in healthy mares to differentiate the effects of withholding feed from the changes potentially associated with the disease. Results Species richness and Shannon diversity (alpha diversity) were significantly lower at the late withheld (10–24 h post withholding feed) and early refed (2–12 h post re-feeding) time points compared to samples from fed horses (P < 0.01). Restoration of species richness and diversity began to occur at the late refed (18–24 h post re-feeding) time points. Horses having feed withheld had a distinct bacterial population compared to fed horses (beta diversity). Bacteroidetes BS11 and Firmicutes Christensenellaceae, Christensenella, and Dehalobacteriaceae were significantly increased in horses withheld from feed primarily during the late withheld and early refed time points. Bacteroidetes Marinilabiaceae and Prevotellaceae, Firmicutes Veillonellaceae, Anaerovibrio, and Bulleidia, and Proteobacteria GMD14H09 were significantly decreased in horses with feed withheld at late withheld, early refed, and late refed time periods (P < 0.01). Changes in commensal gut microbiota were not significant between groups. Conclusions Withholding feed has a significant effect on faecal bacterial microbiota diversity and composition particularly following at least 10 h of withholding feed and should be taken into consideration when interpreting data on the equine faecal bacterial microbiota in horses.

Background Rates of detecting ≥1 potential enteric pathogens (PEP) or toxins (PEP‐T) in feces, blood, or both of horses ≥6 months of age with enteric disease and impact of multiple detections on outcome of horses with colitis has not been reported. Objective To determine detection rates of PEP/PEP‐T in feces, blood, or both of horses with enteric disease and effect of detecting multiple agents on outcome of horses with colitis. Animals Thirty‐seven hundred fifty‐three fecal samples submitted to IDEXX Laboratories and 239 fecal and blood samples submitted to Michigan State University's Veterinary Diagnostic Laboratory (MSUVDL). Methods Retrospective evaluation of PEP/PEP‐T testing results was performed to determine rates of detection of 1 or more PEP/PEP‐T. Impact of detecting multiple agents on outcome was assessed in 239 horses hospitalized for colitis. Results One or more PEP/PEP‐T was detected in 1175/3753 (31.3%) and 145/239 (60.7%) of samples submitted to IDEXX Laboratories and MSUVDL, respectively. In a hospitalized cohort, survival to discharge was lower (76%) in horses with 1 agent, compared to horses with either no (88%) or multiple (89%) agents. There was no difference (P = .78) in days of hospitalization between horses with 0 (1–17), 1 (1–33), and > 1 positive (1–20) result. There was no difference in cost of hospitalization (P = .25) between horses with 0 ($2357, $1110‐15 553), 1 ($2742, $788‐11 005), and >1 positive ($2560, $1091‐10 895) result. Conclusions and Clinical Importance Detection rates of PEP/PEP‐T in horses with colitis vary with cohorts and tests performed. Detection of more than 1 PEP or PEP‐T did not affect outcome.

We investigated the effects of season and geographic location on detection of nucleic acids of potential enteric pathogens (PEPs) or their toxins (PEP-Ts) in feces of horses ≥6-mo-old in the United States. Results of 3,343 equine diarrhea PCR panels submitted to Idexx Laboratories for horses >6-mo-old were reviewed. Submission months were grouped into 4 seasons, and states were grouped into 4 geographic regions. Logistic regression was performed to assess effects of season and region on detection rates of PEPs and PEP-Ts. Agresti–Coull CIs were determined. Detection rate of Salmonella enterica was higher in the South in summer compared to all other regions, and was also higher in the South in fall compared to the Midwest and Northeast. The Neorickettsia risticii detection rate was lower during summer in the West and higher in fall in the Midwest. Detection of Cryptosporidium spp. was lower during spring, summer, and winter in the West. Differences were not identified for detection rates of Clostridioides difficile, Clostridium perfringens, Lawsonia intracellularis, Rhodococcus equi, equine rotavirus, and equine coronavirus. Overall, our data support seasonal and regional differences in detection rates of S. enterica, N. risticii, and Cryptosporidium spp. in horses ≥6-mo-old in the United States.

A 13-year-old multiparous Quarter Horse mare was presented to the Michigan State University’s, Large Animal Emergency service for dystocia. Clinical evaluation revealed a minimally dilated cervix on vaginal examination, with a palpable deceased fetus. Postmortem evaluation following owner-elected humane euthanasia revealed a circumferential, tan, fibrous band at the base of the uterine body that constricted the uterus and was adhered to the left and right ovaries. A routine histologic section of the incarcerating cord attached to the ovary consisted predominately of dense fibrous connective tissue, large blood vessels, and a central oviduct suggestive of a rent in the broad ligament. To the authors’ knowledge, this is the first case report to describe uterine body constriction that precluded vaginal delivery of a fetus in a late gestation mare.