Ventral Colon Research Articles

Electrointestinography, ultrasonographic contractility, and borborygmi of the cecum and colon are not altered by a single episode of hand walking exercise in healthy horses.

To evaluate the effect of hand walking exercise on myoelectrical activity and contractility in normal, healthy horses. Prospective experimental design. A convenience sample of 8 horses were randomized to a control or hand walking treatment group; each horse underwent both treatments. After a 30-minute baseline electrointestinography (EIG), horses were stall rested or hand walked for 15 minutes. Electrointestinography was repeated immediately and at 2 hours. Ultrasonography and auscultation monitored cecal and left ventral colon (LVC) contractions during EIG. Electrointestinography spectral analysis obtained dominant frequency (DF), dominant power (DP), total power (TP) frequency distribution, and changes in slow-wave rhythmic activity. The median (IQR) DF in cycles per minute (cpm) was higher for the cecum (2.067 cpm; IQR, 0.633 cpm) compared to the LVC (2.0 cpm; IQR, 0.396 cpm) but was unchanged by either treatment. Cecal DP (0.0086 mV; IQR, 0.0070 mV) was higher than LVC DP (0.0068 mV; IQR, 0.0051 mV) in the hand walking group, but DP and TP were unaffected by either treatment over time. Borborygmi at all time points were unchanged in both treatment groups. Ultrasonographic contractions were similar across time in both treatment groups and correlated with borborygmi (ρ = 0.63). Dominant power did not correlate with contractions or borborygmi (P > .2081). Brief hand walking as a single strategy to increase gastrointestinal motility did not affect contractility or EIG in normal horses. Fasting and stall rest may not represent the spectrum of severity of gastrointestinal stasis observed in clinical cases. This model is directly applicable to horses fasted prior to surgical procedures.

Gene Expression Analysis before and after the Pelvic Flexure in the Epithelium of the Equine Hindgut.

Previous research demonstrated the distribution of distinct microbial communities in the equine hindgut surrounding the pelvic flexure. The current study evaluated gene expression in epithelial tissues surrounding the pelvic flexure to characterize patterns that might correlate with microbial distribution. Gene expression was determined by analyzing RNA sequence data from the pelvic flexure, the left and right ventral colon, and the left and right dorsal colon. An average of 18,330 genes were expressed across the five tissues sampled. Most of the genes showed some level of expression in all five tissues. Tissue-restricted patterns of expression were also observed. Genes with restricted expression in the left ventral and left dorsal colons have communication, signaling, and regulatory functions that correlate with their known physiology. In contrast, genes expressed exclusively in the pelvic flexure have diverse functions. The ontology of genes differentially expressed between the pelvic flexure and the surrounding tissues was associated with immune functions and signaling processes. Despite being non-significant, these enrichment trends were reinforced by the functions of statistically significant expression differences between tissues of the hindgut. These results provide insight into the physiology of the equine hindgut epithelium that might influence the microbiota and its distribution.

Flowmetry and spectrophotometry can detect reduced intestinal microperfusion in nonsurvivors during equine colic surgery for large intestinal strangulation.

To evaluate the use of laser Doppler flowmetry and spectrophotometry (LDFS) for large intestinal viability assessment in horses with naturally occurring large intestinal strangulations. By use of LDFS, intestinal microperfusion was quantified as tissue oxygen saturation (tSo2), hemoglobin (tHB), and blood flow (tBF) in cases with large colon volvulus and small colon strangulations undergoing colic surgery (n = 17). Intestinal biopsies were taken from the pelvic flexure in all large colon cases and in small colon cases that underwent intraoperative euthanasia. Measurements were compared between survivors and nonsurvivors, and the correlation between LDFS and (immuno)histology was tested (P < .05). The tSo2 and tBF were clearly lower and tHB was higher than previously reported in healthy horses. Following correction of the lesion, pelvic flexure tBF was significantly lower than that of the left ventral colon. Prior to correction of the lesion, microperfusion did not differ between survivors and nonsurvivors, but following release of the strangulation the survivors had a significantly higher tSo2 and tBF compared to the nonsurvivors. There was a negative correlation between tBF and interstitium-to-crypt ratio and a positive correlation between tHB and the histological hemorrhage score. There were no significant correlations between LDFS measurements and inflammatory cell counts or hypoxia-inducible factor-1α immunoreactivity. Large intestinal microperfusion was decreased in nonsurvivors compared to survivors and was correlated with histological injury, suggesting that LDFS has the potential to predict tissue injury and postoperative survival. The use of LDFS as an ancillary diagnostic aid may improve intraoperative viability assessment during colic surgery.

Molecular species determination of cyathostomins from horses in Ireland

Cyathostomins are globally important equine parasites, responsible for both chronic and acute pathogenic effects. The occurrence of mixed infections with numerous cyathostomin species hinders our understanding of parasite epidemiology, host-parasite dynamics, and species pathogenicity. There have been few studies of cyathostomin species occurring in horses in Ireland, where temperate climatic conditions with year-round rainfall provide suitable conditions for infection of grazing animals with bursate nematodes. Here, we amplified and sequenced the ITS-2 region of adult worms harvested at post-mortem from eleven adult horses between August 2018 and June 2020, and recorded species prevalence and abundance of worms recovered from the caecum, right ventral colon and left dorsal colon, using both BLAST and IDTAXA for taxonomic attribution. Phylogenetic relationships and community composition were also recorded and compared with other relevant studies, including a global meta-analysis. Overall, our results agree with previous studies that there does not seem to be a major difference in cyathostomin species occurrence in equids in different geographical regions. We confirmed the results of other workers in relation to the difficulties in discriminating between Cylicostephanus calicatus and Coronocyclus coronatus on the basis of ITS-2 sequences.

Nonsteroidal antiinflammatory drugs reduce anion secretion and increase apoptosis in equine colonic mucosa ex vivo.

Right dorsal colitis causes chronic colic associated with long-term treatment with nonsteroidal antiinflammatory drugs (NSAIDs). This study was designed to determine if NSAIDs could inhibit anion transporters that protect against intestinal mucosal injury in other species. 20 healthy horses. The effects of indomethacin (INDO) and firocoxib (FIR), on short-circuit current (Isc) in mucosa from the right dorsal colon (RDC) and right ventral colon (RVC) were measured in Ussing chambers by standard electrophysiological techniques. Immunohistochemical methods were used to detect apoptosis (caspase-3) with these NSAIDs and phenylbutazone (PBZ) and to locate the NKCC1 transporter. The Isc in RDC and RVC incubated with INDO or FIR was increased almost 3-fold (P < .0001) by prostaglandin E2 (PGE2) through a system inhibited by loop diuretics (P < .0001). Although these findings and anion replacement studies were consistent with anion secretion, the RDC also displayed an Isc response suggestive of a unique transporter apparently absent in RVC or NSAID-free solutions. In RDC, FIR, INDO, and PBZ induced apoptosis in the lower half of crypts. However, significant differences in apoptotic index were recorded in the RDC between NSAID-treated and control tissues (no NSAID). The effects of NSAIDs on Isc were consistent with reduced anion secretion, which could represent the pharmacological equivalent of the transport failure responsible for Cystic Fibrosis (CF) in other species. Failure of anion secretion could interfere with buffering acid from intraluminal fermentation, which could suggest a treatment target for right dorsal colitis.

Colon resection and anastomosis as treatment of an idiopathic colo‐colic intussusception in an adult horse

SummaryAn 18‐year‐old Thoroughbred gelding was referred for further investigation and treatment of acute colic. Exploratory celiotomy was recommended based on the degree of suspected large colon distension on rectal palpation, and only transient reprieve from colic signs following analgesia. This subsequently revealed an intussusception affecting the left dorsal colon (LDC) with the orad LDC (intussusceptum) within the aborad LDC (intussuscipiens). The intussusception, approximately 20 cm in length, was obstructing the colon. Following exteriorisation, reduction of the intussusception was performed, but marked thickening of the colon wall and luminal obstruction led to the decision to perform a partial colon resection of the left dorsal and ventral colon and side‐to‐side anastomosis. The gelding made an unremarkable recovery from anaesthesia and progressed well post‐operatively. Histopathology found no clear cause of the intussusception. Follow‐up (11 months post‐operatively) confirmed complete recovery and the horse had returned to the previous level of light exercise.

Ex vivo evaluation of a novel suture loop method for equine intestinal biopsies.

To compare a novel suture loop method for intestinal biopsies (SLB) with a two-layer, hand-sutured biopsy (HSB) technique in equine small and large intestines. Experimental, randomized, ex vivo study. Eight healthy adult horses. The duodenum, aboral jejunum, and ventral and dorsal large colon were harvested after euthanasia and divided into three sections each. The sections were randomized to SLB, HSB, or control (C, no biopsy) groups. Tissue samples were excised after placement of a suture loop formed by a 4S Roeder knot and oversewn with a Cushing pattern using barbed suture (SLB), or a simple continuous pattern oversewn with a Cushing pattern (HSB). Intraluminal diameter was assessed with contrast radiographs; bursting pressure and wall tension were determined using a solid-state sensor after instillation of fluid. Tissue samples were evaluated by a board-certified pathologist. Tissue samples were full thickness with similar depth and quality (p > .3). Changes in intraluminal diameter did not differ between methods (p > .16). The bursting pressures were higher for controls than biopsied sections (p < .009) but were not different between biopsy methods (p = .998). Bursting wall tension was higher for controls (p < .02) and was similar for both biopsy methods (p = .852). The SLB was equivalent to HSB in strength and effect on intraluminal diameter. The HSB samples were larger and more likely to contain mucosa/villi for histologic diagnosis. The SLB method can be adapted for laparoscopic surgery to obtain both small and large intestinal biopsies. Further investigation is needed before clinical use.

Large intestinal ganglioneuromatosis in a juvenile Arabian filly: Management and long‐term follow‐up

SummaryAn 11‐month‐old Arabian filly was presented for chronic diarrhoea, ill‐thrift and intermittent colic. Abdominal ultrasonography revealed multifocal regions of marked colonic wall thickening. Exploratory laparotomy confirmed multifocal, multi‐sized nodular and segmental intramural mass‐like lesions affecting the right ventral and transverse colon, respectively. Locally extensive regions of mural thickening in the aborad transverse colon resulted in severe luminal restriction (&lt;2.5 cm) and subsequent obstruction of the orad transverse and right dorsal colons with impacted feed material. The lesions were unresectable and full‐thickness biopsy samples were submitted for histopathological evaluation. The filly was subsequently diagnosed with transmural intestinal ganglioneuromatosis of the right ventral and transverse colons. The filly was successfully conservatively managed over a 24‐month follow‐up duration. Management consisted of long‐term dietary modifications in the form of a low‐bulk diet, as well as enteral laxatives and a tapering course of corticosteroids postoperatively. This is the first case of intestinal ganglioneuromatosis in veterinary literature that was (1) diagnosed in a juvenile horse, (2) successfully medically managed and (3) followed up for more than 12 months.

Colonic T-cell-rich, large B-cell lymphoma associated with equid herpesvirus 5 infection and secondary trans-colonic fistula in a horse.

A 17-y-old Rocky Mountain gelding was presented to the Virginia-Maryland Veterinary Teaching Hospital because of a 4-wk history of anorexia, weight loss, lethargy, and fever of unknown origin. Abdominal ultrasound revealed lymphadenomegaly of the abdominal and colonic lymph nodes, thickening of the wall of the large colon, and a mass associated with the large colon. The horse was euthanized given a poor prognosis. On autopsy, an ~20-cm diameter mass was found within the mesocolon between the right ventral and right dorsal colon. The mass had invaded through the colonic walls and formed a fistula between the 2 involved lumina. On histologic evaluation, the mass consisted of small numbers of large neoplastic lymphocytes, numerous small lymphocytes, and many foamy macrophages. A diagnosis of T-cell-rich, large B-cell lymphoma was made based on immunohistochemical staining for CD79a, CD3, and Iba1; concurrent infection with equid herpesvirus 5 was confirmed with in-situ hybridization (ISH). To our knowledge, neither a trans-colonic fistula resulting from alimentary lymphoma in a horse nor detection of intralesional equid herpesvirus 5 in equine alimentary lymphoma by ISH has been reported previously.

Impact of a 24 h feed withdrawal on active nutrient transport, intestinal morphology and gene expression in the equine small and large intestine

Abstract Horses are often subjected to short term feed withdrawal (FW) pre- or post-surgery to reduce anesthetic complications. However, removing nutrients from the intestinal lumen may negatively impact intestinal health. Thirteen horses were used to determine the effects of a 24 h FW on gut barrier function, active nutrient transport, transporter gene expression and intestinal morphology. Following 0 or 24 h FW (0FW or 24FW, respectively), horses were euthanized via overdose of sodium- pentobarbital and –phenytoin, and segments of proximal jejunum (PJ), mid jejunum (MJ), ileum (Il) and right ventral colon (RVC) were harvested for histology (PJ and Il), gene expression, and active nutrient transport analysis. Active transport measurements were determined using modified Ussing chambers following the addition of glucose, phosphorus, glutamine and Gly-Sar. Carbachol induced chloride (Cl) ion secretion was measured to examine the diarrhetic response. Messanger RNA expression of the intestinal Na-dependent glucose cotransporter (SGLT1), fructose transporter (GLUT5), di- and tri-peptide transporter (PepT1) and neutral AA/glutamine transporter (ASCT2) were determined using RT-PCR. The GLM procedure of SAS was used to determine the effects of FW and responses among various intestinal sections. The horse served as the experimental unit. Villus heights (P &amp;lt; 0.002) and crypt depths (P &amp;lt; 0.02) in the Il were larger than in the PJ, though no differences were observed between 0FW and 24FW horses. Active glutamine absorption increased 82% in the PJ of 24FW horses compared to 0FW horses (P &amp;lt; 0.02). The mRNA expression of SGLT1 decreased (P &amp;lt; 0.05) moving aborally in the gastrointestinal tract. Horses subjected to 24FW had 82% less GLUT5 (P &amp;lt; 0.05) and 61% less PepT1 mRNA expression in the PJ, compared to 0FW horses. Interestingly, ASCT2 mRNA expression increased 164% from PJ to RVC (P = 0.05). However, a 36% decrease in ASCT2 mRNA expression was observed overall for 24FW horses. This data indicates that SGLT1, GLUT5, PepT1 and ASCT2 are expressed throughout the small intestine and RVC of the horse at varying concentrations, and that they can be differentially regulated by a 24 h FW. Data from this experiment also indicates that a 24 h FW results in up regulation of active glutamine absorption, presumably in an effort to supply glutamine as an energy substrate for enterocytes.

Integrated multi-omics reveals novel microbe-host lipid metabolism and immune interactions in the donkey hindgut.

Evidence has shown that gut microbiota play a key role in host metabolism and health; however, little is known about the microbial community in the donkey hindgut as well as the interactions that occur between gut microbes and the host. This study aimed to explore the gut microbiome differences by analyzing the microbial community and differentially expressed genes (DEGs) related to lipid metabolism and the immune system along the donkey hindgut. The hindgut tissues (cecum, ventral colon, and dorsal colon) were separated, and the contents of each section were collected from six male donkeys for multi-omics analysis. There were significant differences in terms of dominant bacteria among the three sections, especially between the cecum and dorsal colon sites. For instance, species belonging to Prevotella and Treponema were most abundant in the cecum, while the Clostridiales_bacterium, Streptococcus_equinus, Ruminococcaceae_bacterium, etc., were more abundant in the dorsal colon. Apart from propionate, the concentrations of acetate, isobutyrate, valerate and isovalerate were all lower in the cecum than in the dorsal colon (p < 0.05). Furthermore, we identified some interesting DEGs related to lipid metabolism (e.g., ME1, MBOAT1, ACOX1, ACOX2 and LIPH) and the immune system (e.g., MUC3B, mucin-2-like, IL17RC, IL1R2, IL33, C1QA, and MMP9) between the cecum and dorsal colon and found that the PPAR pathway was mainly enriched in the cecum. Finally, we found a complex relationship between the gut microbiome and gene expression, especially with respect to the immune system, and combined with protein-protein interaction (PPI) data, suggesting that the PPAR pathway might be responsible, at least in part, for the role of the hindgut microbiota in the donkeys' gut homeostasis. Our data provide an in-depth understanding of the interaction between the microbiota and function in the healthy equine hindgut and may also provide guidance for improving animal performance metrics (such as product quality) and equine welfare.

Comparison of the host response to larvicidal and nonlarvicidal treatment of naturally acquired cyathostomin infections in horses.

This study aimed to collect information on local and systemic inflammatory responses, and goblet cell-associated components, following anthelmintic treatment with moxidectin and ivermectin in horses naturally infected with cyathostomin parasites. Thirty-six horses aged 2-5 years of age were randomly allocated to three groups. Group 1 received ivermectin/praziquantel (0.2mg/kg), Group 2 received moxidectin/praziquantel (0.4mg/kg) and Group 3 were untreated controls. Tissue samples from the Cecum, Dorsal and Ventral Colons were used for histopathological evaluation and preserved for RNA isolation and gene expression analysis. Whole blood was collected weekly for gene expression analysis as well. The control group had significantly higher inflammation associated with higher larval scores. The treatment groups displayed no differences in larval counts and inflammatory cell populations (p > .05). Mucosal larval counts were positively correlated with goblet cell hyperplasia scores (p=.047). The moxidectin-treated group had a significantly lower expression of IFN-γ (p < .05). The data suggest that removal of cyathostomins reduced the pro-inflammatory response associated with cyathostomin infections. Pro-inflammatory reactions associated with anthelmintic treatment were minimal, but lowest for moxidectin-treated horses. Results suggested that cecum, ventral and dorsal colons responded differently to cyathostomin larvae, which may have implications in the disease process.

Mechanisms of bicarbonate secretion in the equine colon ex vivo.

To examine bicarbonate (HCO3-) secretion ex vivo in the equine large colon to determine any differences between the right dorsal colon (RDC) and right ventral colon (RVC). The effect of phenylbutazone (PBZ) on HCO3- secretion was examined in the RDC. 14 healthy horses. In anesthetized horses (n = 10), segments of mucosa from RDC and RVC were harvested to measure HCO3- secretion ex vivo with the pH Stat method. The effect of PBZ on HCO3- secretion in the RDC was studied in 4 additional horses. Three distinct mechanisms of HCO3- secretion previously described in a murine model were confirmed in the equine colon. The RDC had a greater capacity for electrogenic, Cl--independent HCO3- secretion than the RVC (P = 0.04). In the RDC, all HCO3- secretion was decreased by PBZ (P < 0.02) but was not studied in the RVC because of low baseline secretion. Secretion of HCO3- by the RDC could play a pivotal role in equine colon physiology, because intense microbial fermentation in this site could require HCO3- secretion to buffer short-chain fatty acids. Inhibition of this secretion by PBZ could interfere with mucosal buffering and predispose to changes associated with right dorsal colitis.

Precision of cyathostomin luminal worm counts: Investigation of storage duration and fixative

Essentially all grazing horses are infected with cyathostomin parasites. Adult cyathostomins reside in the large intestine of the horse and larval stages encyst within intestinal mucosa. Manual worm collection from aliquots of intestinal content is the current gold standard for retrieval and enumeration of luminal parasites, however, no research has been conducted to standardize specific parameters for processing and storage of samples. The aims of this study were (1) to evaluate the precision of current standard operating procedures for enumeration of luminal adult cyathostomin populations, (2) investigate the influence of chosen fixative, either 70 % ethanol or 10 % buffered formalin, as well as storage duration, immediately post necropsy vs. stored for eight weeks, on the magnitude and precision of worm counts, and (3) compare the luminal count magnitude between the three intestinal segments (cecum, ventral colon, dorsal colon). Ten miniature horses were enrolled in this study for euthanasia and necropsy over a four-week period. Luminal worm counts were conducted for 2 % aliquots of the cecum, ventral colon, and dorsal colon and samples were allocated to the two fixatives and the two storage durations. Precision was evaluated by coefficient of variation (CV) and was 13.04 % for total cyathostomin counts. Mean CV for large intestinal segments ranged from 15.31 % to 52.50 % irrespective of fixative used or storage duration. cecum worm counts were significantly lower compared to the ventral colon (p = 0.008) and dorsal colon (p = 0.01). Fixative and storage duration were not statistically associated with count precision or magnitude. This study demonstrated moderate to high precision estimates for luminal cyathostomin worm counts but did not identify any effects of fixative and storage duration within the framework of the study. This is the first study to determine cyathostomin worm count precision, and results will be useful for power analyses in the future.

Comparative Analysis of Bacterial Diversity between the Liquid Phase and Adherent Fraction within the Donkey Caeco-Colic Ecosystem.

Simple SummaryThe bacteria residing in donkey hindgut are clearly divided into two distinct ecological sites: liquid phase (Lq) and adherent fraction (Ad). Though both the Lq and Ad bacteria play an important role in feed digestion, the Ad bacteria have not previously been specifically sampled or directly compared with the Lq bacteria. The present study was conducted to comparatively analyze the bacterial community composition between the Lq and Ad fraction within the donkey caeco-colic ecosystem. The results showed that the relative abundance of Bacteroidota, Spirochaetota, Fibrobacterota and Patescibacteria in the Ad fraction was greater than the Lq fraction, indicating that bacteria associated with plant biomass are mainly responsible for plant fiber degradation. Regarding the genus level, the liquid phase presented higher abundance in Lactobacillus compared to Ad fraction. The activities of enzymes related to fiber degradation were predicted by PICRUSt, and they were also higher in Ad bacteria than Lq. In addition, the bacterial community composition was also distinct within the donkey caecum, ventral colon and dorsal colon. The present study provides evidence that bacteria adherent to feed particles may be better at plant fiber degradation than Lq bacteria due to the greater cellulolytic populations and activities.Donkey hindgut is an enlarged fermentative chamber that harbors a highly complex and extremely abundant community of anaerobic bacteria. It can be divided into two different ecological sites: liquid (Lq) phase and adherent fraction (Ad) colonized by bacteria. However, the Ad bacteria have not previously been specifically collected or directly compared with the Lq bacteria. In the present study, the digesta collected from the caecum, ventral colon and dorsal colon of nine Dezhou donkeys was separated into Lq and Ad fractions. The bacterial community structure was comparatively determined using 16S rRNA gene sequences by Illumina MiSeq. The Ad bacteria had a higher bacterial diversity than Lq bacteria due to the higher Chao and ACE index (p < 0.05). The predominant bacteria at the phylum level were Firmicutes (55.4~74.3%) and Bacteroidota (13.7~32.2%) for both the Lq and Ad fraction. The relative abundance of Bacteroidota, Spirochaetota, Fibrobacterota and Patescibacteria in the Ad fraction was greater than Lq (p < 0.05), suggesting that bacteria associated with feed particles were mainly responsible for plant fiber degradation. At the genus level, the abundance of Lactobacillus in Lq was greater than that in the Ad fraction (p < 0.05), indicating that the bacteria in the Lq fraction were better at hydrolyzing readily fermentable carbohydrates. PICRUSt showed that the activities of enzymes related to fiber degradation in the Ad fraction were also greater than Lq. In addition, the hindgut region also had a significant effect on the bacterial community composition. The relative abundance of Rikenellaceae_RC9_gut_group, Clostridium_sensu_stricto_1, Christensenellaceae_R-7_group and norank_Bacteroidales_BS11_gut_group was increased (p < 0.05) along the donkey hindgut. In summary, the present study provides evidence that bacteria adherent to plant biomass were different to those in the liquid phase within the donkey caeco-colic digesta, and bacteria associated with feed particles may mainly be responsible for plant fiber degradation.

Leukocyte numbers and intestinal mucosal morphometrics in horses with no clinical intestinal disease.

Healthy horses and other animals have large numbers of resident leukocytes in the intestinal wall, but there is scant information regarding which and how many leukocytes are normally present in the equine intestinal wall. Our aim was to provide a reference range of leukocytes in the intestinal mucosal and submucosal propria of normal horses. We included in our study intestinal tissues from 22 Thoroughbred racehorses with no clinical intestinal disease, which had been euthanized because of catastrophic musculoskeletal injuries. Neutrophils, lymphocytes, eosinophils, macrophages, and plasma cells were counted in 5 random 17,600-µm2 areas of villus lamina propria of the duodenum, jejunum, and ileum, and deep lamina propria of the duodenum, jejunum, ileum, right ventral colon, left ventral colon, left dorsal colon, right dorsal colon, and small colon. Other features investigated in the same intestinal segments included villus height and width (small intestine), presence of ciliated protozoa, Paneth cells number, subcryptal leukocyte layers (number of leukocyte layers between the bottom of the crypts and the muscularis mucosae), and submucosal leukocytes. Lymphocytes were the most numerous cells in all segments analyzed, followed by plasma cells, eosinophils, macrophages, and neutrophils. Eosinophil numbers were significantly higher in both lamina propria and submucosa of the large intestine than in the small intestine. The duodenum had shorter and thinner villi than either jejunum or ileum. The data provided from our study will be useful for diagnosticians examining inflammatory processes in the intestinal tract of horses.

The degradation of four different horse feeds in vitro previously evaluated in ponies in vivo

Total tract in vivo digestibility values give no information on the manner or site of feed degradation. However, the site and mode of feed degradation may differ between feeds yielding similar nutrient profiles and digestibility values, with potential consequences for equine metabolic health. Here, the course of in vitro fermentation of three subtly different complementary feeds with the same in vivo dry matter (DMD) and gross energy (GED) digestibilities [Winergy Equilibrium High Energy (WEH), Buckeye EQ8 Gut Health (EGH) and Spillers Power Cubes (SPC)] and grass hay was monitored via the evolution of head space gas, to determine between-feed differences in fermentation parameters. In experiment 1, ground feeds (WHOLE) or their residues remaining after incubation with pepsin/HCl and pancreatin (PRE) were incubated with an equine fecal inoculum (F). In experiment 2, feeds were sequentially incubated with digesta from the equine stomach (G) small intestine (SI) and right ventral colon (RVC) all obtained at an abattoir from animals euthanised for non-research purposes. Feed in vitro dry matter digestibilities (IVDMD) were also determined post-incubation with pepsin, pancreatin and F (experiment 1), and after incubation with G, SI and RVC (experiment 2). Incubation with pepsin and pancreatin resulted in substantially elevated IVDMD of all feeds compared with G and SI digesta. The end-point IVDMD of the three complementary feeds incubated with F or RVC were the same within inoculum type. The total gas evolved during the fermentation of HAY with either F or RVC was lower (P < 0.001) than that of the three complementary feeds. EGH yielded less gas and had longer T50 [time taken (h) for evolution of 50 % of total gas] (P < 0.001) than WEH or SPC when incubated with RVC, and yielded (P < 0.001) longer lag and slower fractional rates than WEH and SPC when incubated with F. This suggests that despite the complementary feeds having the same in vivo DMD and GED, EGH was the most slowly fermented by both F and RVC. Such information may help identify which of several apparently similar feeds may be the most suitable for equines prone to nutritionally elicited metabolic disorders, enabling more refined and targeted ration formulation for such animals.

A retrospective study of gastrointestinal disorders in a predominantly Austrian leisure horse referral hospital population

SummaryThe aim of our retrospective study was to produce and analyse epidemiological data on gastrointestinal (GI) disorders of Austrian leisure horses. Case records of horses referred to the Equine Clinic of the Veterinary University of Vienna were collected from an electronic hospital information system using its search options. All cases reported to have suffered a GI disorder between March 2003 and February 2015 were selected. In this period of 4314 days, data of 1833 GI cases, mostly accompanied by colic signs, were analysed. The vast majority of our GI cases appeared in the abdominal parts of the GI tract 96% (1760/1833) while just 1.3% (24/1833) could be definitively attributed to oesophageal disorders, whereas in 2.7% (49/1833) of the cases a definitive diagnosis could not be made. The highest prevalence of GI disorders was seen in July and October/November. A breakdown of figures for cases clustered under the colic syndrome showed that colon impactions in left ventral large and/or pelvic flexure (35%) were the major problem followed by gastric disorders (18%), spasmodic colic (9%), enteritis (7%), caecal tympany (6%); caecal impaction (4%), colitis (3%), abnormal anatomical positions of large colon including complete and partial strangulation/volvulus, nephrosplenic entrapment of the left ventral and dorsal colon and right dorsal displacement of the large colon (3%) and small intestinal volvulus (2.7%). In 12% of the cases, the cause of the abdominal discomfort was likely idiopathic paralytic ileus. The searching tool of the electronic patient data also brought up cases with malabsorbtion/IBD syndrome and GI ruptures, both these contributed less than 1% of the referred GI cases. Results suggested that the causes of colic are diverse, but the major reasons for referred cases of colic in the east Austrian horse population are large colon impaction or displacements. Seasonal distribution and specific causes of gastrointestinal disorders should be considered essential components of the initial clinical assessment of horses presenting with colic.

33 Profiling miRNA transcripts in the equine hindgut by quantitative PCR

Gastrointestinal (GI) homeostasis in a horse results from dynamic interactions between a horse's gut physiology and the microbes in the various compartments. MicroRNAs (miRNA), single-stranded 20–22 basepair RNA molecules involved in post-transcriptional control of gene expression, have been implicated as an essential mechanism for control of gastrointestinal physiology and communication between host and microbe. Researchers have described how host-derived miRNAs influence microbial communities' composition in the GI. We have recently described how the pelvic flexure separates distinct microbial populations in the equine hindgut and subsequently have wondered if equine miRNA transcripts expressed by GI tissues could have a role in maintaining this separation. Investigations to characterize miRNAs' expression profile and other non-coding RNAs in the equine GI tract are limited. To address this, it is critical that we first know something about the expression of non-coding transcripts in the equine GI. This study investigated miRNA expression in tissues of the hindgut surrounding the pelvic flexure. RNA was isolated from the intestinal epithelium of 3 4-year-old American Quarter Horses collected from the right and left ventral colon (VC), pelvic flexure (PF), and right and left dorsal colon (DC). The miRNA transcripts were reverse transcribed using the miScript II RT kit, and relative abundance was quantified using the miScript SYBR Green PCR kit and primer sets for 286 annotated mature equine miRNAs. Biological replicates were pooled, and differential expression was determined following normalization by the delta Ct = Ct(target) – Ct(sample) method. A total of 230 miRNA transcripts were expressed in at least one GI location, with 60 expressed in all 5 locations. Twenty-eight transcripts had expression restricted to a single site, 5 of which were only expressed in the pelvic flexure. Additionally, 42 transcripts have patterns of expression across a subset of anatomical locations. Notably, 10 transcripts were expressed in the VC and PF, 5 transcripts were expressed in the DC and PF, and 15 transcripts were expressed in the VC and DC but not PF. Pathway and target analysis for the miRNAs with compartment restricted expression was performed using DIANA TOOLS. Of note, miRNA transcripts expressed only in the PF were predicted to target genes in the Hippo signaling pathway, which is associated with the regulation of intestinal tissue proliferation and homeostasis. Further investigation of miRNA expression in the equine hindgut will improve our understanding of gastrointestinal homeostasis's regulatory processes.

138 Expression profiling of the ventral colon, pelvic flexure, and dorsal colon epithelium by RNA-seq

The equine large intestine is essential for nutrient absorption and as a location for microbial digestion. The pelvic flexure is an important anatomical landmark that divides distinct microbial communities in the equine hindgut. Previous work from our group showed that several taxonomic groups were restricted to the cecum and ventral colon. Since no physical barrier separates these compartments from the more distal areas, we became curious about alternative mechanisms that support the segregation of different microbial groups. Physiological differences in each compartment likely result in different requirements from the microbiota at each location. This study evaluated gene expression in the mucosal and submucosal layers of the right and left ventral colon (VC), pelvic flexure (PF), and right and left dorsal colon (DC). Samples were collected from 3 4-year-old American Quarter Horses, and total RNA was isolated. Single-end libraries were prepared using the NEBNextⓇ Ultra II Directional RNA library kit and sequenced on an IlluminaⓇ NextSeq 550 platform. The sequencing generated an average of 22.5 million reads per sample (range 14.5 to 30.9). Gene expression analysis was performed using the Galaxy platform by aligning quality trimmed sequence reads to EquCab3 using the HISAT2, assembling transcripts with StringTie, and quantifying transcript abundance with Salmon. DESeq2 was used to assess differential expression between the intestinal compartments. Expression (present in 2 of 3 biological replicates) was detected in at least one intestinal compartment for 21,987 transcripts and ranging from 14,766 to 15,134 transcripts per sample. A total of 13,944 transcripts were detected in all 5 areas, and 739 transcripts demonstrated a tissue-restricted expression pattern (detected above threshold in only on anatomical location). Gene ontology was used to identify the functional roles of transcripts expressed in all or only one hindgut compartment. Transcripts expressed in all tissues were associated with internal cell metabolic processes, which are common despite cell type. In contrast, transcripts with tissue-restricted expression patterns were associated with cellular differentiation and secretion processes. Matrix metalloproteinases, transcription factors, and integrin proteins were identified as differentially expressed (P < 0.05) in the PF compared with the surrounding VC and DC compartments. Continued investigation of these transcripts in the equine hindgut will enhance our understanding of digestive physiology and support future studies of interactions between host and microbiota.