Colic is a leading cause of death in horses, with the most fatal form being strangulating obstruction which directly damages the intestinal barrier. Following surgical intervention, it is imperative that the intestinal barrier rapidly repairs to prevent translocation of gut bacteria and their products and ensure survival of the patient. Age-related disparities in survival have been noted in many species, including horses, humans, and pigs, with younger patients suffering poorer clinical outcomes. Maintenance and repair of the intestinal barrier is regulated by a complex mucosal microenvironment, of which the ENS, and particularly a developing network of subepithelial enteric glial cells, may be of particular importance in neonates with colic. Postnatal development of an immature enteric glial cell network is thought to be driven by the microbial colonization of the gut and therefore modulated by diet-influenced changes in bacterial populations early in life. Here, we review the current understanding of the roles of the gut microbiome, nutrition, stress, and the ENS in maturation of intestinal repair mechanisms after foaling and how this may influence age-dependent outcomes in equine colic cases.

BackgroundEquine coronavirus (ECoV) leads to outbreaks with variable morbidity and mortality. Few previous reports of risk factors for infection are available in the literature.ObjectivesTo describe unique clinical findings and risk factors for infection and development of clinical disease.Animals135 horses on a farm affected by ECoV outbreak.MethodsRetrospective cohort study. Data obtained included age, breed, gender, activity level, housing, and feed at the onset of the outbreak. Factors were evaluated for assessment of risk of infection using simple logistic regression or Fisher's exact test. Significance was set at p ≤ 0.05.Results and findingsForty-three of 54 (79.6%) horses tested on the farm were positive on fecal PCR for ECoV, and 17 horses (12.6%) developed clinical signs consistent with ECoV. Out of 17 horses in which the presence or absence of signs of colic was noted, 6 of 17 (35.3%) showed signs of colic. Three of these horses had small colon impactions, 2 of which required surgical intervention. Significant risk factors for having positive PCR results included being primarily stalled (OR 167.1, 95% CI 26.4–1719), housing next to a positive horse (OR 7.5, 95% CI 3.1–19.0), being in work (OR 26.9, 95% CI 4.6–281.9), being fed rationed hay vs. ad libitum (OR 1,558, 95% CI 130.8–15,593), and being fed alfalfa hay (OR 1,558, 95% CI 130.8–15,593).Conclusions and clinical importanceThis report describes risk factors for ECoV infection many of which were associated with intensive management of show horses. Clinicians should be aware that clinical signs vary and can include severe colic.

The enteric nervous system consists of a dense, complex network of neurons and glia which are instrumental in the maturation of normal intestinal physiology after birth. Our lab uses a comparative pig model to study the postnatal development of the enteric glial network and its role in regulating intestinal barrier functions in neonates. Immunolabeling‐enabled three‐dimensional (3D) imaging of solvent‐cleared organs (iDISCO) is a method of preparing tissue samples for volume imaging with a light sheet microscope. iDISCO has been optimized for use in primarily mouse organs and embryos for the study of early development and offers a more complete picture of the tissue than traditional histological analysis. Our objective was to optimize the iDISCO protocol for use in porcine intestinal tissue to allow complete qualitative and quantitative analysis of postnatal development of the enteric glial network in our comparative pig model. Antibodies against glial cell markers S100b, Sox10, and glial fibrillary acidic protein (GFAP) were used to triple‐stain fixed full‐thickness 3mm by 5mm samples of porcine jejunum using the iDISCO protocol. Samples were imaged with a light‐sheet microscope (Ultra‐II, LaVision BioTec®) using three different fluorescent channels and datasets were visualized and analyzed in 3D with Imaris software (Oxford Instruments®). The percent volume of GFAP+ glial cells was quantified by manually masking individual intestinal villi and optimizing a surface algorithm to identify glial network structures within those villi. Antibodies against all three markers tested produced the predicted staining pattern with minimal non‐specific staining. Percent of jejunal villus volume occupied by GFAP+ glia is higher in 6‐week‐old versus 2‐week‐old pig (0.49% versus 0.23%, *P≤0.05). Ongoing work will optimize quantification techniques for S100b and Sox10, and assess co‐localization patterns of these glial markers in the jejunum at discrete timepoints postnatally. iDISCO is a powerful imaging modality which will allow our lab to directly assess the expansion, complexity, and localization of glial cell subtypes by marker co‐expression analysis at discrete postnatal timepoints, and will be utilized in future studies to explore effects of disease and external interventions on the enteric glial network. Support or Funding Information NIH P30 DK034987 UNC CGIBD Pilot Feasibility; NIH T32 5T32DK007737‐22 UNC Basic Science GI Research Training Fellowship; USDA National Institute of Food and Agriculture, Animal Health Projects 1007263 and 07985; 2017 NC State CMI TPP Seed Grant

Lower survival has been reported in foals than adults with small intestinal strangulating obstruction (SISO), but age-dependent outcomes have not been examined directly. Hospital records were collected from five US academic referral hospitals. It was hypothesized that foals would exhibit lower survival than case-matched adults. Foal cases 6-months-of-age or younger, and adult cases between 2- and 20-years-of-age were collected. Data revealed 24 of 25 (96.0%) foals and 66 of 75 (88.0%) adults that were recovered from surgery for SISO survived to hospital discharge. Sixteen of the total 41 (39.0%) foals studied were euthanized intraoperatively, whereas 30 of 105 (28.6%) adults were euthanized intraoperatively. Common lesions in foals that were recovered from surgery were volvulus (n = 13) and intussusception (n = 5), whereas common lesions in adults were volvulus (n = 25) and strangulating lipoma (n = 23). This study was limited by incomplete medical records, relatively small sample size, and lack of long-term follow-up. Unexpectedly, short-term survival tended to be higher in foals than adults and may have been partly driven by case selection prior to referral or surgery or decision-making intraoperatively. More optimism toward surgical treatment of foals with SISO may be warranted.

In our pig intestinal ischemia model, a neonatal defect in epithelial barrier restitution in the jejunum can be rescued by ischemic mucosal homogenate from weaned pigs. This is associated with an immature enteric glial cell (EGC) network, a known driver of restitution that matures postnatally partly in response to microbial colonization, which can be modulated with dietary prebiotic fiber. Therefore, we hypothesized that dietary oligosaccharide supplementation accelerates postnatal microbial colonization and EGC network maturation in the jejunum and colon, thus enhancing restitution after ischemic injury. After 24‐hours of colostrum, piglets were fed control or oligosaccharide‐supplemented formula (control‐fed or prebiotic‐fed) for 21 days and fecal swabs were sequenced for 16S rDNA. Intestinal samples were collected for western blot, imaging, and EGC culture. Surgically ischemia‐injured jejunal and colonic mucosal samples from select day 14 pigs were recovered ex vivo while monitoring epithelial barrier function by transepithelial electrical resistance (TEER). Migration abilities, calcium responses to ATP, paracrine effects on IPEC‐J2 cell restitution, and protein secretome were assessed in jejunal and colonic EGC cultures. Colonic microbial taxa changed in a time‐ and diet‐dependent manner with the prebiotic‐fed taxa clustering by day 7 and becoming progressively more tightly clustered over time (P<.050). TEER and histology of uninjured jejunum and colon were unaffected by diet. Following ischemia, low initial TEER recovered to control levels in the control‐fed colon but not prebiotic‐fed colon (diet and injury interaction, P=.038), while diet had no effect on jejunal TEER recovery. Prebiotic‐fed colon had lower levels of the EGC markers glial fibrillary acidic protein (GFAP) and S‐100B at day 21 (P<.050), and subjectively reduced density of GFAP+ and S‐100B+ EGC were noted in preliminary volume imaging of prebiotic‐fed jejunal submucosa at days 14 and 21. EGC from prebiotic‐fed colonic submucosa showed decreased chemotactic motility toward sterile‐filtered colonic contents (P=.010), decreased intracellular calcium response to ATP (P=.0075), and their co‐culture with IPEC‐J2 enhanced epithelial restitution versus monoculture (P=.032). Oppositely, EGC from prebiotic‐fed jejunal submucosa showed increased intracellular calcium response (P=.050) and their co‐culture with IPEC‐J2 did not enhance restitution as efficiently (P=.33) as those from control‐fed jejunal submucosa (P=.019). For future study, prebiotic‐fed colonic submucosal EGC differentially secreted 13 proteins of interest versus control‐fed. Preliminary results indicate dietary oligosaccharides in neonates exert different effects in the jejunum versus the colon on EGC network development and phenotype, and on epithelial restitution in vivo and in vitro. Ongoing work to understand microbiome‐ EGC‐epithelial interactions during postnatal development may lead to novel preventative and clinical practices to improve intestinal health in vulnerable neonates.