Differences in the equine faecal microbiota between horses presenting to a tertiary referral hospital for colic compared with an elective surgical procedure.

BACKGROUND: The faecal microbiota is emerging as potentially important in intestinal disease. More research is needed to characterise the faecal microbiota from horses with colic. OBJECTIVES: To compare the relative abundance of bacterial populations comprising the faecal microbiota in horses presenting for colic compared with an elective surgical procedure. STUDY DESIGN: Prospective observational clinical study. METHODS: Admission faecal samples were collected from horses presenting for colic and elective surgical procedures. Faecal samples were extracted for genomic DNA, PCR- amplified, sequenced and analysed using QIIME. Species richness and Shannon diversity were estimated for each faecal sample. The extent of the relationship between bacterial communities (beta diversity) was quantified using pairwise UniFrac distances, visualised using principal coordinate analysis (PCoA) and statistically analysed using PERMANOVA. The relative abundance of bacterial populations between the two treatment groups were compared using ANCOM. RESULTS: Faecal bacterial communities in horses presenting for colic had fewer species (P<0.001) and lower diversity (P<0.001) compared with horses presenting for elective surgical procedures. Based on the PERMANOVA analysis, there was a significant difference in the bacterial community composition between horses admitted for colic vs. elective procedures (P = 0.001). Based on ANCOM test, at the genus level, 14 bacterial lineages differed between the two groups. The relative abundance of known commensal bacteria including Prevotella, Clostridia, Lachnospiraceae were reduced whereas Christenellaceae, Streptococcus and Sphaerochaeta were increased in horses with colic when compared with elective cases. MAIN LIMITATIONS: Relative low numbers and a diverse population of horses. CONCLUSIONS: Changes in bacterial populations in the faecal microbiota of horses presenting for colic observed in this study concurs with previous studies in veterinary and human patients with gastrointestinal disease. Future studies focusing on different causes of colic, chronic or recurrent disease, and the association with histological changes within the intestine are needed. The Summary is available in Portuguese - see Supporting Information.

Multicentre, blinded, randomised clinical trial comparing the use of flunixin meglumine with firocoxib in horses with small intestinal strangulating obstruction.

BACKGROUND: Small intestinal strangulating obstruction (SISO) is associated with endotoxaemia which leads to an increased risk of death. Nonsteroidal anti-inflammatory drugs (NSAIDs) are used to treat signs of endotoxaemia by inhibiting cyclo-oxygenases (COX). COX-1 is expressed constitutively and promotes gut barrier function, whereas COX-2 is inducible and contributes to the signs of endotoxaemia. In preclinical SISO trials, intestinal barrier recovery was more complete with reductions in endotoxin permeability in horses treated with COX-2 selective NSAIDs as compared with horses treated with flunixin meglumine. OBJECTIVES: We hypothesised that treatment of post-surgical SISO horses with firocoxib (COX-2 selective) would reduce the signs of endotoxaemia to a greater extent than flunixin meglumine (nonselective COX inhibitor) while continuing to provide similar levels of pain control. STUDY DESIGN: Blinded randomised clinical trial. METHODS: In addition to clinical monitoring, preoperative and 12-, 24- and 48-h post-operative plasma samples were assessed for prostaglandin E2 (PGE2 ), thromboxane B2 (TXB2 ), TNF⍺ and soluble CD14 (sCD14). RESULTS: In 56 recruited SISO horses, either flunixin meglumine (1.1 mg/kg, i.v., q12h) or firocoxib (0.3 mg/kg, i.v. loading dose; 0.1 mg/kg, i.v., q24h) was given in the post-operative period in three university hospitals from 2015 to 2017. COX-2 selectivity was confirmed by a relative lack of inhibition of the COX-1 prostanoid TXB2 by firocoxib and significant inhibition by flunixin meglumine (P = 0.014). Both drugs inhibited the COX-2 prostanoid PGE2 . There were no significant differences in pain scores between groups (P = 0.2). However, there was a 3.23-fold increased risk (P = 0.04) of increased plasma sCD14 in horses treated with flunixin meglumine, a validated biomarker of equine endotoxaemia. MAIN LIMITATIONS: Horses were all treated with flunixin meglumine prior to referral. In addition, many horses were treated with lidocaine, which has been shown to mitigate the deleterious effects of flunixin meglumine. CONCLUSIONS: In SISO cases, firocoxib reduced a biomarker of endotoxaemia as compared with flunixin meglumine while continuing to provide similar levels of pain control.

Assessing gastrointestinal motility in healthy horses comparing auscultation, ultrasonography and an acoustic gastrointestinal surveillance biosensor: a randomised, blinded, controlled crossover proof of principle study.

BACKGROUND: Auscultation and ultrasonography are noninvasive techniques used to assess gastrointestinal motility in horses. Recently, noninvasive acoustic gastrointestinal surveillance (AGIS) biosensors evaluating intestinal motility have been validated in humans. OBJECTIVES: To compare AGIS to auscultation and ultrasonography for detecting decreased motility after xylazine administration. STUDY DESIGN: Randomised, blinded, controlled cross-over proof of principle study. METHODS: Six healthy horses were evaluated under fasted and nonfasted conditions and randomly assigned to receive treatment with 0.4 mg/kg xylazine or an equivalent volume of 0.9% NaCl intravenously. After a 48-h washout period, the process was repeated with the alternate treatment. Motility was assessed pre and posttreatment. Borborygmi were assessed in each abdominal quadrant and graded on a scale of 0-3, with 3 being continuous borborygmi. Duodenal, jejunal and caecal contractions were assessed ultrasonographically in consistent locations. Four AGIS biosensors were applied in standardised locations (duodenum, caecum, ventral midline, right dorsal colon). The biosensors measure acoustic signals and data were recorded in transport metric. Data were analysed using cross-classified multilevel random effects logistic regression including area under the receiver operator characteristic curve (AUC ROC). Sensitivity, specificity and accuracy were calculated for each modality. RESULTS: All three modalities detected a reduction in gastrointestinal motility following xylazine administration with AUC ROC being 0.85, 0.84 and 0.86 for auscultation, ultrasonography and AGIS respectively. The sensitivity, specificity and accuracy for auscultation was 88, 71 and 75%; for ultrasonography was 67, 63 and 64%; and for AGIS was 69, 70 and 70%, respectively. MAIN LIMITATIONS: The study was performed in normal healthy horses and application of this device to clinical patients warrants further investigation. CONCLUSIONS: In this proof of principle study, AGIS was able to discriminate between horses given xylazine from those given 0.9% NaCl with comparable accuracy as auscultation and ultrasonography. The Summary is available in Spanish - see Supporting Information.

Are horse age and incision length associated with surgical site infection following equine colic surgery?

It is our clinical impression that age and incision length are more strongly associated with surgical site infection (SSI) following colic surgery than skin closure or wound protection method. Therefore, the objective of this observational clinical cohort study was to identify the risks for SSI in horses undergoing colic surgery. Data collection included pre-, intra-, and postoperative variables. Variables with P < 0.2 following univariable analysis were used in a logistic regression multivariable model. Variables with P <0.05 were included in the final model. Odds ratios (OR; 95% confidence intervals, 95% CI) were determined. The area under the curve (AUC) for the receiver-operator characteristic was calculated. The final multivariable model included breed (P = 0.008), incision length (P = 0.004), surgical procedure classification (P <0.001), and postoperative (PO) colic (P = 0.037; overall model P <0.001, and AUC was 0.81 [excellent discrimination between SSI vs. no SSI]). Warmbloods (OR 12.0; 95% CI 2.7-74.8), American breeds (OR 6.4; 95% CI 1.2-43.0), and Thoroughbreds (4.5; 95% CI 1.1-25.5) more commonly had SSI than other breeds (ponies/miniature horses, Draft breeds, Standardbreds, Arabians, and Crossbreeds [referent]). A higher SSI rate was associated with incision lengths >27 cm (3.7; 95% CI 1.5-9.9), heavily contaminated procedures (12.0; 95% CI 3.3-49.9), and horses with PO colic (2.7; 95% CI 1.1-6.8). SSI appeared to be more common after heavily contaminated procedures and in horses with PO colic, which probably resulted in more incisional contamination and trauma. Some breeds appeared to have higher odds of SSI. Age was not associated with SSI. The risk of developing SSI was higher for horses with an incision >27 cm; therefore, surgeons are encouraged to use the minimum incision length required to accomplish the necessary abdominal exploration and bowel manipulation in the safest manner possible.

Comparison of short- and long-term complications and survival following jejunojejunostomy, jejunoileostomy and jejunocaecostomy in 112 horses: 2005-2010.

REASONS FOR PERFORMING THE STUDY: There is disagreement among surgeons over whether jejunoileostomy (JI) or jejunocaecostomy (JC) is the better method of anastomosis following proximal ileal resection. OBJECTIVE: To compare short- and long-term complications and outcome in horses undergoing jejunojejunostomy (JJ), JI and JC and to test the hypotheses that a higher proportion of horses undergoing JI would have short-term complications and mortality compared with horses undergoing JC or JJ and that JC would be associated with a higher long-term mortality and occurrence of colic. STUDY DESIGN: Retrospective cross-sectional study. METHODS: Medical records of horses undergoing celiotomy for a small intestinal obstruction and JJ, JI or JC from 2005 to 2010 were reviewed. Post operative complications were recorded. Short-term outcome was alive vs. dead at hospital discharge and was analysed using a Chi-squared test. Long-term follow-up was obtained and a Kaplan-Meier estimate of the survivor function was performed. RESULTS: There were 112 horses included. A higher proportion of JI horses had a repeat celiotomy during hospitalisation compared with horses undergoing JC. The number of horses alive at hospital discharge was not different between groups: JJ 79% (95% confidence interval [CI] 68-90%), JI 78% (95% CI 61-96%), JC 83% (95% CI 71-96%). Among horses discharged with long-term follow-up, more horses had colic after JC compared with JJ or JI. Long-term post discharge survival based on the Kaplan-Meier survivor function was lower for horses undergoing JC than JJ or JI (P = 0.04). CONCLUSION: While there was no difference in short-term outcome between groups, more horses with JI underwent a repeat celiotomy during hospitalisation. Horses with a JC were more likely to have long-term complications with colic. Horses that were subjected to euthanasia because of colic within 12 months of hospital discharge either had a JC or repeat celiotomy. The results suggest that, when possible, a JI may be the preferred method of anastomosis based on more favourable survival and lower occurrence of colic long term.

Effects of a novel hydrogel on equine bone healing: a pilot study.

OBJECTIVE: To examine the efficacy and biocompatibility of a thiolated gelatin-thiolated carboxymethyl hyaluronan (CMHA-SGX) sponge as an osteoconductive device in an equine second and fourth metacarpal bone defect model. METHODS: Seven millimetre segmental ostectomies were created bilaterally in the second and fourth metacarpal bones of four horses. The left and right metacarpal defects were randomly assigned to (1) be filled with a CMHA-SGX sponge (treated) or (2) were left unfilled (control). The duration of the study was nine weeks. Bone healing was evaluated using serial radiology, as well as histologically and histomorphometrically. Data were analyzed using an analysis of variance (ANOVA). The level of significance was p<0.05. RESULTS: Serial radiographic evaluation revealed improved healing in the treated compared to the control defects at weeks eight and nine (p = 0.02). This finding was not corroborated histologically. Histomorphometry did not reveal any significant differences in healing between experimental groups. The CMHA-SGX sponge did not inhibit bone formation, induce local inflammation or lead to surgical site infection. CLINICAL SIGNIFICANCE: While further optimization to improve osteoconductive properties should be considered, the CMHA-SGX sponge appears to be a biocompatible orthopaedic implant and its use as a carrier for osteogenic proteins warrants further investigation.

Post operative infection, pyrexia and perioperative antimicrobial drug use in surgical colic patients.

REASONS FOR PERFORMING STUDY: Infections are common complications in post operative colic patients. It is the impression of some surgeons that pyrexia in the early post operative period is a sign of infection and appropriate timing of perioperative antimicrobials will decrease the incidence of post operative infection. OBJECTIVE: To determine the association between 1) post operative pyrexia and development of infection and 2) perioperative antimicrobial drug use and infection rate in post operative colic patients. METHODS: Medical records of patients undergoing surgical treatment for colic were reviewed. Horses recovering from surgery and surviving >48 h were included. Data relating to case details, duration of surgery, post operative infection, peri- and post operative antimicrobial administration, presence, intensity and duration of pyrexia, were recorded. Data were analysed using standard statistical methods for simple comparisons between groups and by logistic regression for more complex comparisons. RESULTS: One-hundred-and-thirteen horses were included in the final analyses, 48 (43%) of which were diagnosed with a post operative infection. Duration of surgery and anaesthesia were associated with post operative infection. Eighty-five percent of horses (n = 96) exhibited pyrexia (rectal temperature >38.3°C) post operatively. Peak temperature >39.2°C, time post surgery to peak temperature >48 h and duration of pyrexia >48 h were significantly associated with infection. In a combined model, time to first pyrexic >48 h post surgery, peak temperature and time to peak >48 h were equally weighted and the model's positive predictive value for post operative infection was 72%. Timing and dose rate of preoperative antimicrobials were not associated with infection but duration of post operative antimicrobial drug use was. CONCLUSION AND CLINICAL RELEVANCE: Slight to mild pyrexia (38-39.4°C) in the early post operative period is not necessarily associated with impending bacterial infection in colic patients and the use of antimicrobials in these patients may be costly and unnecessary.

Colic in geriatric compared to mature nongeriatric horses. Part 1: Retrospective review of clinical and laboratory data.

REASON FOR PERFORMING STUDY: It is the impression of some surgeons that geriatric horses have a lower survival rate compared to mature nongeriatric horses following colic surgery. One possible reason for this is that geriatric horses may be more critically ill at admission and have more severe disease than mature nongeriatric horses. OBJECTIVE: To compare admission historical, physical examination and laboratory data for geriatric and mature nongeriatric horses referred for signs of colic. METHODS: Medical records of horses admitted with a presenting complaint of colic between 2000 and 2006 were reviewed. Geriatric horses ≥16 years (n = 300) and mature nongeriatric horses 4-15 years (n = 300). Information obtained included duration of colic prior to admission, admission level of pain, heart rate, intestinal borborygmi, packed cell volume (PCV), plasma creatinine and blood lactate concentrations and peritoneal fluid total protein. Data were analysed using a Chi-squared test or an analysis of variance. Level of significance was P<0.05. RESULTS: There was no difference between geriatric and mature horses in the duration of colic prior to admission or in admission heart rate, PCV, or plasma creatinine or blood lactate concentrations. However, geriatric horses were more likely to be moderately painful and less likely to be bright and alert than mature horses; and less likely to have normal intestinal borborygmi than mature horses. Peritoneal fluid total protein concentration was higher in geriatric than mature horses. CONCLUSIONS AND POTENTIAL RELEVANCE: Geriatric horses presenting with signs of colic had a similar admission cardiovascular status based on heart rate, PCV, and plasma creatinine and blood lactate concentration to mature horses. Geriatric horses, however, may have different causes of colic, which may be more serious than mature horses based on pain, lack of intestinal borborygmi and peritoneal fluid total protein concentration.

Colic in geriatric compared to mature nongeriatric horses. Part 2: Treatment, diagnosis and short-term survival.

REASON FOR PERFORMING STUDY: Owners and veterinarians are often concerned about mortality of geriatric horses following colic surgery. OBJECTIVE: To compare treatment, diagnosis and short-term survival for geriatric compared to mature nongeriatric horses with colic. METHODS: Medical records of horses admitted with a presenting complaint of colic between 2000 and 2006 were reviewed. Geriatric horses were aged ≥16 years (n = 300) and subcategorised as age ≥20 years (n = 134). Mature nongeriatric horses were age 4-15 years (n = 300). Information obtained included medical (included horses subjected to euthanasia without surgery) vs. surgical management, lesion location, type and classification, surgical procedures performed and short-term survival. Data were analysed using a Chi-squared test or an analysis of variance. Level of significance was P<0.05. RESULTS: The overall short-term survival of geriatric horses was lower than that for mature horses (59 vs. 76%, respectively). The survival of medically managed geriatric horses was lower than that for mature horses (58 vs. 80%, respectively). The survival of surgically managed geriatric horses was not different to that for mature horses (59 vs. 70%, respectively) except for geriatric horses age ≥20 years (53%). There was no difference in survival between geriatric and mature horses with small (86 and 83%, respectively) or large (78 vs. 70%, respectively) intestinal strangulating lesions or those undergoing jejunojejunostomy (75 vs. 70%, respectively). Geriatric horses with a large colon simple obstruction had a lower survival compared to mature horses (80 vs. 97%, respectively). CONCLUSIONS AND POTENTIAL RELEVANCE: The survival of geriatric horses with a strangulating lesion or requiring jejunojejunostomy was not different to that for mature horses. Geriatric horses presenting with colic were more likely than mature horses to be subjected to euthanasia without surgery (i.e. lower survival with medical treatment). Geriatric horses undergoing surgery for a large colon simple obstruction had a lower survival than mature horses.

Short-term outcome of equine emergency admissions at a university referral hospital.

REASONS FOR PERFORMING STUDY: Obtaining data on emergency admission survival rates is important to provide clients with an estimate of prognosis and to identify areas in which improvements in case management can be achieved. OBJECTIVE: To determine the short-term outcome of equine emergency admissions to a university referral hospital during a 12 month period. METHODS: Short-term outcome was defined as survival to discharge or died/euthanasia during hospitalisation. The overall death (euthanasia) rate was calculated; and rate for horses with different categories of: age; admission month, day and time; presenting complaint (PC); duration of clinical signs prior to presentation; clinical pathology abnormalities; and therapy/therapeutic-related procedures performed was recorded. RESULTS: There were 918 admissions. The overall death rate was 24%. Foals (34%) and geriatric (40%) subjects had a death rate that was higher than that for mature horses (21%, referent). The death rate was highest in March (37%). Horses with a PC categorised as neurological (46%) or neonatal (41%) had the highest and as ophthalmological (5%) or trauma/skin (13%) the lowest death rates. There was no difference in death rate between different admission days or times or the duration of clinical signs prior to presentation. The death rates for horses with abnormal peritoneal fluid (71%), coagulopathy (63%), acid-base abnormalities (52%), hypoproteinaemia (47%), dehydration (43%), hypoxia/hypercapnia (48%), leucopenia (44%), electrolyte abnormalities (39%), hyperlactataemia (39%) or azotaemia (35%) were high. The death rate for horses treated with intranasal oxygen (57%), plasma (34%) or polymixin B (35%) was high and for horses undergoing laceration repair/joint (0%) or synovial cavity lavage (4%) was low. CONCLUSIONS: Age and critical illness were important contributing factors to a higher death rate. POTENTIAL RELEVANCE: Improving the understanding of disease processes in and developing treatment strategies for neonatal and geriatric patients as well as critically ill patients is required.

Blood culture status in mature horses with diarrhoea: a possible association with survival.

REASONS FOR PERFORMING STUDY: The incidence and implications of positive blood cultures in mature horses with diarrhoea is unknown. The diagnosis of bacteraemia may alter treatment and prognosis. HYPOTHESIS: The proportion of horses with diarrhoea that are blood culture positive is higher than previously assumed and a positive blood culture has a negative impact on survival. METHODS: Blood cultures were taken at admission and 24 h after admission from 31 mature horses with diarrhoea. RESULTS: Nine (29%) horses were blood culture positive within 24 h of admission. Organisms isolated included Corynebacterium spp. (n = 6), Streptococcus spp. (n = 2), Pantoea agglomerans (n = 1), Gram-negative rod (n = 1), Bacillus spp. (n = 1) and yeast (n = 1). Horses with positive blood cultures were significantly less likely to survive. Prior treatment with antimicrobial drugs had no significant effect on blood culture status. Horses with positive blood cultures had a significantly higher heart rate, packed cell volume (PCV) and plasma potassium concentration at admission, and a higher PCV and lower total plasma protein concentration 24 h after admission. CONCLUSIONS: Positive blood cultures occur more frequently than previously reported, and may have a negative impact on survival in horses with diarrhoea. POTENTIAL RELEVANCE: Results of blood cultures may be useful in formulating a prognosis for horses with diarrhoea. Further research is required to determine the effect of antimicrobial treatment on outcome.

Complications and survival associated with surgical compared with medical management of horses with duodenitis-proximal jejunitis.

REASONS FOR PERFORMING STUDY: Based on clinical observation, it is hypothesised that horses with duodenitis-proximal jejunitis (DPJ) that are treated surgically have a shorter duration, smaller volume, and slower rate of nasogastric reflux (NGR) compared to horses treated medically, are more likely to develop diarrhoea than medically managed cases, and have a higher incisional infection rate than a sample population of horses undergoing abdominal exploration for gastrointestinal disease other than DPJ. OBJECTIVES: To compare: 1) duration, volume and rate of NGR and the percentage of horses with diarrhoea between medically and surgically treated DPJ cases; and 2) incisional infection rate in horses with DPJ undergoing abdominal exploration to a sample population of horses undergoing abdominal exploration for gastrointestinal disease other than DPJ. METHODS: Medical records of cases with DPJ diagnosed 1995-2006 were reviewed. Information obtained included subject details, presenting clinical findings, treatment category (medical/surgical), complications (diarrhoea, incisional infection), and outcome (survival/nonsurvival). Data were analysed using a Chi-squared test and a mixed model analysis of variance. Level of significance was P<0.05. RESULTS: Compared to medical cases, surgical cases had significantly decreased survival, a longer duration and larger total volume of NGR, and were more likely to develop diarrhoea. The incisional infection rate for horses with DPJ undergoing abdominal exploration was 16% compared to 7% for the sample population of horses. CONCLUSIONS: Surgical treatment of horses with DPJ did not lead to resolution of NGR faster than medical treatment. Surgical cases were more likely to develop diarrhoea and did not have a significantly higher incisional infection rate than the sample population.

Long-term study of partial arytenoidectomy with primary mucosal closure in 76 Thoroughbred racehorses (1992-2006).

REASON FOR PERFORMING STUDY: The effectiveness and best method to perform a partial arytenoidectomy in racehorses is unclear. This study was performed to evaluate the success of and complications that can occur after a unilateral partial arytenoidectomy with primary mucosal closure in Thoroughbred racehorses. HYPOTHESIS: Partial arytenoidectomy is an effective surgical procedure to return Thoroughbred racehorses, afflicted by arytenoid chondropathy or a failed laryngoplasty, to preoperative levels of performance. METHODS: Seventy-six Thoroughbred racehorses admitted to the New Bolton Centre between 1992 and 2006 were assessed. Information was obtained from the medical records about the horse, laryngeal abnormalities, surgery and other findings during hospitalisation. Racing information was evaluated relative to those independent variables by an analysis of variance with a level of significance of P<0.05. RESULTS: Arytenoid chondropathy was the presenting complaint in 54 horses and failed laryngoplasty in 22 horses. Thirteen horses (17%) underwent a second surgery for laser excision of intralaryngeal granulation tissue at the arytenoidectomy site. Seventy-three horses were discharged from the hospital and racing outcome was evaluated. Sixty horses (82%) raced after surgery and 46 horses (63%) raced 5 or more times after surgery. The median time from surgery to the first start was 6 months. The average earnings/start was not significantly different before and after surgery. There was no association between earnings after surgery and age, gender, location of lesion, type of lesion, duration of tracheal intubation or undergoing a second surgery. CONCLUSIONS AND POTENTIAL RELEVANCE: A Thoroughbred racehorse is likely to race after a unilateral partial arytenoidectomy with primary mucosal closure and return to a preoperative level of performance.

Growth factor and receptor mRNA expression in the intestine of horses with large colon volvulus: a pilot study.

REASONS FOR PERFORMING STUDY: Growth factors (GF) are important for maintenance and repair of intestinal mucosal structure and function, but there have been no studies investigating growth factor (GF) or growth factor receptor (GF-R) mRNA expression in the intestine of horses with large colon volvulus (LCV). OBJECTIVES: (1) To determine mRNA expression for epidermal growth factor (EGF), EGF receptor (EGF-R), insulin-like growth factor-I (IGF), IGF receptor (IGF-R), vascular endothelial growth factor (VEGF) and VEGF receptor (VEGF-R) in the intestine of horses with an LCV compared to normal intestine. (2) To measure the correlation between histological intestinal injury and mRNA expression. METHODS: In 5 horses, samples were collected from the mid-jejunum (small intestine, SI), pelvic flexure (PF) and right dorsal colon (RDC) prior to creation of the LCV (NORM), 1 h following creation of the LCV (ISCH) and 1 h following correction of the LCV (REPER). In 2 clinical cases of LCV, samples were collected from the PF and RDC. Samples were assessed histologically for the amount of intestinal injury. The mRNA expressions of growth factors and receptors were determined using qRT-PCR. RESULTS: VEGF and VEGF-R mRNA expression was greater in horses with an LCV compared to NORM. Expression of IGF-R mRNA increased in the SI during ISCH and REPER. CONCLUSION AND POTENTIAL RELEVANCE: The increase compared to NORM in VEGF and VEGF-R mRNA expression in horses with LCV may be important in early intestinal healing and may also explain, in part, the increase in vascular permeability in horses with a LCV. Expression of IGF and IGF-R in the SI warrants further investigation and may be important for understanding post operative complications in horses with SI lesions.

Myosin heavy chain composition in normal and atrophic equine laryngeal muscle.

The myosin heavy chain (MHC) composition of a given muscle determines the contractile properties and, therefore, the fiber type distribution of the muscle. MHC isoform expression in the laryngeal muscle is modulated by neural input and function, and it represents the cellular level changes that occur with denervation and reinnervation of skeletal muscle. The objective of this study was to evaluate the pattern of MHC isoform expression in laryngeal muscle harvested from normal cadavers and cadavers with naturally occurring left laryngeal hemiplegia secondary to recurrent laryngeal neuropathy. Left and right thyroarytenoideus (TA) and cricoarytenoideus dorsalis (CAD) were obtained from 7 horses affected with left-sided intrinsic laryngeal muscle atrophy and from 2 normal horses. Frozen sections were evaluated histologically for degree of atrophy and fiber type composition. MHC isoform expression was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of muscle protein. Histologic atrophy was seen in all atrophic muscles and some right-sided muscles of 3 affected horses, as well as the left TA of 1 normal horse. Fiber type grouping or loss of type I muscle fibers was observed in the left-sided laryngeal muscles in all but 1 affected horse, as well as in the right muscles of 2 affected horses, and the left TA of 1 normal horse. SDS-PAGE showed 2 bands corresponding to the type I and type IIB myosin isoforms in the CAD and TA of the 2 normal horses. Affected horses demonstrated a trend toward increased expression of the type IIB isoform and decreased expression of the type I isoform in atrophic muscles. This study confirmed the presence of histologic abnormalities in grossly normal equine laryngeal muscle, and it demonstrated an increased expression of type IIB MHC with a concurrent decreased expression of type I MHC in affected muscles. Evaluation of muscle fiber changes at the cellular level under denervated and reinnervated conditions may aid in assessing future strategies for reinnervation or regeneration of atrophic laryngeal muscle.

Prevalence of gastric squamous ulceration in horses with abdominal pain.

REASONS FOR PERFORMING STUDY: Prevalence of gastric ulcerations differs widely according to breed and circumstances of management. Further study of the biological variables involved is required in order to identify more exactly the reasons for the reported range. OBJECTIVES: The objectives of this present study, which do not appear to have been addressed previously in the literature, were 1) the prevalence of gastric ulceration in horses with abdominal pain. 2) difference in prevalence in horses responding to medical therapy and those requiring surgical intervention. 3) whether gastric ulceration is associated with any particular gastrointestinal tract lesion. METHODS: Horses were included in the study if gastroscopy was performed within 24 h of presentation. The presence and grade of gastric ulceration was recorded together with the medical records. Data were analysed categorically using a Fisher's exact test or Chi-squared test. RESULTS: One hundred horses met the selection criteria. Forty-nine percent (49/100) of horses had gastric ulceration, 63% (63/100) responded to medical therapy and 37% (37/100) to surgical intervention, and prevalence was higher in the former (59%) than the latter (32%). Horses with duodenitis-proximal jejunitis (DPJ) had a trend towards higher prevalence of gastric ulceration compared to those with other GI lesions. Sixty-eight percent (13/19) of horses diagnosed with DPJ, 32% (8/25) with a large colon impaction and 14% (1/7) with large colon volvulus had gastric ulceration. CONCLUSIONS: The presence of gastric ulceration in all horses with abdominal pain was moderate. Horses responding to medical therapy had a higher prevalence of gastric ulceration compared to horses requiring surgery and there was a trend towards higher prevalence in cases of DPJ compared to other GI lesions. There was not a statistically significant difference in gastric ulceration detected between specific lesions, including large colon impactions and large colon volvulus. POTENTIAL RELEVANCE: The clinical relevance of ulceration is still unclear and further studies are required to differentiate between incidental and clinically important gastric ulceration.

Ex vivo comparison of a novel tapered-sleeve and traditional full-limb transfixation pin cast for distal radial fracture stabilization in the horse.

Distal radial fractures in adult horses are examples of long-bone fractures that are not always amenable to internal fixation. These fractures are often open, contaminated, severely comminuted, and located adjacent to the antebrachiocarpal joint. There have been few studies to improve upon the methods of stabilization of this type of fracture. External coaptation incorporating transfixation pins is one method that has been used to stabilize distal radial fractures in horses (1-3). The purpose of this preliminary study was to compare the load to failure in simulated weight-bearing of a novel tapered-sleeve transfixation pin cast (TSTPC) (4) with the traditional transfixation pin cast (TPC) in an ex vivo distal radial fracture model. Ten adult equine cadaveric forelimbs were randomly placed into a TPC group (n = 5) or a TSTPC group (n = 5). An oblique distal radial osteotomy was created prior to application of fibreglass cast material. The limbs were loaded in a single cycle to failure in simulated weight-bearing using an axial load. The mean load to failure for the TSTPC group (35,814 N) was significantly greater than in the TPC group (22,344 N) (p = 0.003). Tapered sleeves in conjunction with TPC warrant further investigation because they may prolong the life of the fixation, prevent or diminish fractures through the pin sites, and increase the load capacity of external coaptation used to stabilize equine fractures.