Bite and kick injuries in horses: prevalence, risk factors and prevention

REASON FOR PERFORMING STUDY: Studies on the prevalence and predisposing factors of bite and kick injuries in horses have not been reported in a population-based data sample. OBJECTIVES: To investigate the prevalence of bite and kick injuries in horses and associated risk factors in a representative sample of horses in Switzerland. METHODS: A questionnaire on the incidence of disease and injury, which included the frequency of bite and kick injuries and their association with breed, housing, use and feeding regime, was sent to 2559 horse owners randomly selected throughout Switzerland. RESULTS: The data of 2912 horses with 897 disorders diagnosed by a veterinarian were analysed. There were 231 injuries, 50 (21.6%) caused by a bite or kick from another horse; this number corresponded to 5.6% of all diseases and injuries and concerned only 1.7% of all the horses evaluated. Warmblood, Thoroughbred and Arabian horses had a 4.3 times higher risk of bite or kick injuries than horses of other breeds. Eighteen per cent of injuries were associated with a change in housing management and occurred regardless of whether horses were kept in groups permanently or sporadically. CONCLUSIONS AND POTENTIAL RELEVANCE: A stable group hierarchy and a housing system that provides adequate space and is adapted to horse-specific behaviour are important factors in prevention and kick and bite injuries.     

Incidence of major injuries, severe colic, and acute laminitis at American Horse Shows Association A- and B-rated shows

A questionnaire was designed to determine the incidence of major injuries, severe colic, and acute laminitis in horses at American Horse Shows Association (AHSA) A- and B-rated shows, ie, those shows requiring a veterinarian in attendance. The questionnaire was sent to the show stewards and filled out by the attending veterinarians of the AHSA A- and B-rated shows held from January 1982 to October 1984. Of 2,952 questionnaires sent out, 799 (27%) were completed and returned by veterinarians; 99 of them were discarded because of incomplete or misleading information. The study revealed a low incidence of major injuries, severe colic, and acute laminitis in horses at AHSA A- and B-rated shows. In 700 horse shows surveyed, there was a total of 231 major injuries, severe colic, or acute laminitis. Considering that the shows surveyed had a median number of 193 horses and a median duration of 3 days, the 231 injuries represent a relatively small number, compared with the general population at risk.     

Idiopathic perforating ulceration of the small intestine in five adult horses

Perforating ulceration of the small intestine was diagnosed in 5 adult horses. Affected horses presented with signs of low‐grade colic, depression and inappetance. Abdominal paracentesis yielded abnormal peritoneal fluid in all cases. Perforating ulcers were located at the mesenteric border in 4 horses and the ileum in one horse. All horses had diffuse septic peritonitis. The aetiology of the condition is unknown.     

Long-term survival of equine surgical colic cases. Part 1: patterns of mortality and morbidity

Postoperative complications and mortality can occur many weeks or months after colic surgery. We are interested in the long-term outcome of these cases. This study documents patterns of mortality and morbidity among 341 horses that recovered from colic surgery March 1998-August 2000. The progress of each horse was rigorously followed by periodic telephone and postal questionnaires. Event time data were recorded for each animal and a total of 321 horse years of survival, together with death from all causes, colic-related death and various postoperative complications. Postoperative survival (of all horses excluding grass sickness cases) was triphasic over the first 600 days and there was marked mortality in the first 10 days postoperatively. The probability of survival postoperatively decreased to 0.87 by 10 days, 0.82 by 100 days and declined slowly to 0.75 at 600 days. Horses suffering from epiploic foramen entrapment had a significantly reduced probability of postoperative survival (RR = 2.1, P = 0.033). The causes of death for 104 horses that died postoperatively and the prevalence of postoperative complications are recorded for the study population. Postoperative colic was the most prevalent complication with 100 horses (29%) suffering one or more episodes. However, only 16 horses (4.6%) suffered 3 or more episodes. The incidence of postoperative colic was 0.55 episodes/horse year at risk. This study provides data that will inform the prognosis for postoperative colic cases and identifies epiploic foramen entrapment as carrying a worse prognosis for survival than other strangulating lesions.     

Risk factors for equine acute abdominal disease (colic): Results from a multi-center case-control study

Many causal hypotheses for acute equine abdominal disease (colic) have been proposed. However, few epidemiologic studies have been undertaken to identify risk factors for the syndrome. Risk factors for equine colic were identified using a hospital-based, multi-center, case-control study. Horses admitted with abdominal pain to Cornell, Guelph, Ohio State, Pennsylvania or Tufts university veterinary hospitals between March and December 1991 were selected. Control horses were randomly selected from a list of all other non-colic admissions. The person(s) responsible for the day-to-day care of the horse completed a telephone questionnaire. Risk factors were identified using multivariable logistic regression analysis.

A total of 406 colic and 406 control horses were used in the final analysis. Age, breed, outdoor access (pasture or drylot), outdoor water supply, use of a daily worming product, amount of concentrates and whole-grain corn consumed, type of person responsible for the day-to-day care of the horse and previous colic history were all significantly associated with colic risk. Arabian horses were more than twice as likely to be colic cases (OR = 2.0, 95% CI = 1.0–3.9), whereas Standardbred horses were nearly half as likely (OR = 0.6, 95% CI = 0.4–1.0) to be colic cases compared with the comparison Thoroughbred group. Horses that had access to outdoor enclosures without a continuous supply of water were more than twice as likely (OR = 2.2, 95% CI = 1.2–4.3) to be colic cases compared with horses that had an adequate supply of water on outside enclosures. The use of a daily worming product for at least 60 days during the 12-month period prior to presentation was associated with a significantly lower colic risk (OR = 0.11, 95% CI = 0.02–0.55). Colic risk increased with greater consumption of whole-grain corn; however, when all non-roughage concentrate feeds were combined, colic risk decreased with increased intake of concentrates. Significant interactions were identified between age and drylot use and between the type of care-person responsible for the day-to-day care of the horse (owner or non-owner) and previous colic history.

The findings of this study illustrate the complex multi-factorial nature of equine colic and point towards the importance of the overall quality of stable management and care, as well as the type of outdoor enclosure (pasture or drylot), water access, carbohydrate intake, parasite control and intrinsic (breed-related) factors.     

Intrathoracic esophageal perforation of unknown cause in four horses

Three horses (age 17 - 23 years) were referred to the equine clinic of the University of Berne due to colic, fever, tachycardia and tachypnea. All horses showed pleural effusion. Clinical findings in 2 of the horses were highly suggestive of an intra-thoracic esophageal perforation. Severe septic pleuropneumonia without suspicion of an esophageal lesion was diagnosed in the 3rd horse. In addition, an 11 year old stallion was referred to the equine clinic for treatment of a presumptive large colon impaction. The horse was given laxatives after nasogastric intubation. Subsequent dramatic clinical deterioration and signs consistent with severe pleuropneumonia suggest that esophageal perforation had occurred when passing the nasogastric tube. All 4?horses were euthanized due to a poor prognosis. Esophageal perforation was diagnosed or confirmed post mortem in all cases. A hypertrophy of the tunica muscularis of the intra-thoracic esophagus was found in 3 of 4?horses.     

A cross-sectional study of colic in horses on thoroughbred training premises in the British Isles in 1997

The aim of this study was to estimate the incidence of colic in horses in Thoroughbred training premises in 1997 in the British Isles. The seasonal pattern and outcome of colic episodes were also investigated, together with any association between premises level variables and colic. Data were collected by a postal questionnaire. The results showed a colic incidence density of 7.19/100 horse years (s.e. 0.42) and a cumulative incidence of colic of 5.80% (s.e. 0.30). Premises were grouped according to whether they had more Flat than National Hunt horses (Flat premises) or more National Hunt than Flat horses (NH premises). A similar rate of colic episodes was found in each group. However, significantly higher cumulative incidences of one episode of colic were found in the Flat premises and of multiple episodes in the NH premises, respectively. The outcome of each episode of colic showed spontaneous recovery in 28.7%, medical recovery in 63.1%, surgical recovery in 2.0% and death in 6.2% of cases. This indicated an overall mortality rate from colic of 0.45 deaths/100 horse years. The seasonal pattern of episodes of colic showed a spring and autumn peak, with significant differences in the seasonal pattern between the Flat and NH premises. Relative risk analysis and logistic regression modelling with random effects showed significant associations between the number of episodes of colic and the number of horses on the premises (allowing for the number of horses on each premises, the larger premises had a decreased risk of colic). After adjusting for the number of horses, 3 other variables were associated with colic; Flat premises (with an increased risk), the owner being the sole person looking after the horses (a decreased risk) and the premises being a combined training and breeding establishment (a decreased risk).     

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

The 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.     

Australian veterinarians who work with horses: an analysis

OBJECTIVE: To define and describe the population of Australian veterinarians who work with horses. METHOD: Questionnaires were mailed to 866 veterinarians who had been identified as working with horses, and 87% were completed and returned. Data were entered onto an Excel spreadsheet, and analysed using the SAS System for Windows. RESULTS: About 12% of Australia's veterinarians were doing all the veterinary work with horses, and about 3% worked exclusively (> 90%) with horses, but did more than half (58%) of the horse work. Veterinarians working with horses included more males (80%) than the veterinary population as a whole (approximately 60%). Males had an average age of 47 years, females 35. Almost all (94%) worked in private practice, with 31% being employees, 28% partners and 41% sole owners. Females were more likely to be employees than males. Males reported working 55 hours/week; females 49. More females (44%) than males (16%) had worked less than full-time for more than a year. Males expected to work for another 12 years in full-time equivalents, and females for 16. One quarter (24%) saw only horses, but treated 58% of total horse cases. One-half had < 25% horses, and 29% had < 10% of horses in their caseloads. More of the older (54% of those aged > 60) than younger respondents (27% of those < 40) had grown up on farms with animals. One-quarter (24%) decided to become a veterinarian while in primary school, and females decided at a younger age than males. Overall, younger respondents decided at a younger age than did their older counterparts. A veterinarian contributed to the decision for 21% of these veterinarians. CONCLUSION: In this survey, Australian veterinarians who work with horses were found to be typically male, and advanced in their careers. As these older veterinarians retire, there may not be enough veterinarians who are committed to and competent with horses to take their places.     

Subepiglottic cysts in 15 horses

Subepiglottic cysts (SECs) are an infrequent cause of upper respiratory tract noise and exercise intolerance in horses. They may also be associated with no clinical signs and be an incidental finding during routine upper airway endoscopy. The aim of this study was to assess the effect on performance of horses undergoing surgical removal of SECs. The case records of 15 horses (1995–2009) diagnosed with SECs were retrieved. Eleven (73%) of the 15 horses included in the study were Thoroughbred racehorses. Eleven (73%) of the 15 horses had no preoperative clinical signs related to the SECs, with the remaining 4 (27%) having a respiratory noise (n = 4), nasal discharge (n = 1), difficulty swallowing (n = 1) or a cough (n = 1). Endoscopic examination in the standing horse was diagnostic in 93% (n = 14) of horses. Nine (82%) of the 11 Thoroughbred horses were yearlings, of which only one horse (11%) presented with clinical signs consisting of a respiratory noise and nasal discharge. Four of the 11 (36%) Thoroughbred horses were found to have concurrent epiglottic entrapment. Surgical removal was successful in all cases. Eight of the 11 (73%) Thoroughbred horses in this study raced following SEC removal. The majority of SECs are identified during routine endoscopic examinations and are not associated with clinical signs. The prognosis following surgical removal of SECs is good and future performance does not appear to be affected.     

A farm-based prospective study of equine colic incidence and associated risk factors

Abdominal pain (colic) in the horse is one of the most acute problems facing equine practitioners. Several causes and risk factors are associated with colic. The current study evaluated the incidence and associated risk factors of colic during a 1-year evaluation in horse farms of Kerman, Iran. The study investigated age, sex, breed, anthelmintic control program, and nutritional status of 128 horses of four breeds on six farms that took part in the study. The mean incidence density rate of colic in the horse population was 8.6% (11/128) in a year. Crossbred horses had more chance of developing colic (P < .05). Horses between the ages of 2 and 10 years also had more risk of developing colic (P < .05). There was no significant difference between sexes (P < .05), and nutritional factors were the most associated risk factors in the cases under study.     

Incarceration of the Small Intestine in the Epiploic Foramen Report of 19 Cases (1983–1992)

The medical records of 19 horses referred for colic and subsequently found (18 confirmed, 1 suspected) to have small intestinal incarceration through the epiploic foramen were reviewed. These horses were of various ages and breeds; they had clinical signs of colic for an average duration of 13.5 hours before examination. Seventeen horses had nasogastric reflux, and 15 had palpable small intestinal distention. Three horses were killed during surgery because of severe intestinal damage. Of the remaining 16 horses, 13 required intestinal resection and anastomosis. The length of incarcerated small intestine varied from 8 cm to 17.6 m. The ileum was involved in 12 cases. In one horse, the mesoduodenum was disrupted before surgery, causing intra-abdominal bleeding; incarceration of bowel was not found during surgery. The short-term (1 month) survival rate was 74% (14 of 19 cases), and the long-term survival rate was 63% (12 of 19 cases). The follow-up period was 3 months to 45 months (mean 17.2 ± 7.2 months).     

A survey of adverse effects associated with ivermectin use in Louisiana horses

In a survey of 13 Louisiana equine practices, it was determined that 366 of 3,316 horses developed adverse reactions following use of ivermectin, with 3 of the horses having more than 1 reaction. Almost all of the reactions were of minor to moderate concern; however, 1 death was reported. Three hundred and thirty-two (91% of all reactions) were reported as ventral midline pruritus or edema (10% of all doses). Fifteen (0.45%) were transient injection site swelling and/or stiffness. Eleven horses (0.33%) developed limb edema. Eyelid edema was reported in 4 horses (0.12%). Two horses (0.06%) had fever. Rate and depth of respiration was increased in 1 horse (0.03%). One horse (0.03%) became disoriented. Three horses (0.09%) developed signs of colic. One horse (0.03%) died a few minutes after injection, and 1 horse (0.03%) became depressed. The survey covered the period from March to August of 1983.     

Treatment of Atrial Fibrillation in Horses: New Perspectives

Forty-one horses were treated for atrial fibrillation (AF) with 22 mg/kg quinidine sulfate via nasogastric tube every 2 hours until conversion to sinus rhythm, a cumulative dose of 88 to 132 mg/kg had been administered in 2-hour increments, or the horse had adverse or toxic effects from the drug. Treatment intervals were prolonged to every 6 hours if conversion had not occurred. Digoxin was administered before treatment if the horse had a fractional shortening ≤ 27% (3 horses), was prone to tachycardia (resting heart rate ≥ 60 beats/min) (1 horse), or had a previous history of sustained tachycardia of over 100 beats/min during prior conversion (3 horses). Digoxin was administered during day 1 of quinidine sulfate treatment if the horse developed a sustained tachycardia of over 100 beats/min during treatment (11 horses) or on day 2 if conversion had not occurred (7 horses). Plasma quinidine concentrations within 1 hour of conversion of AF to sinus rhythm ranged from 1.7 to 7.5 μg/mL (mean, 4.05± 1.6) and ranged from 1.7 to 4.7 μg/mL in 97% of horses. Most horses (92%) with plasma quinidine concentrations > 5 μg/mL exhibited an adverse or toxic effect of quinidine sulfate (clinical or electrocardiographic). There was no statistical association between plasma quinidine concentrations and sustained tachycardia (> 100 beats/min), diarrhea, or colic. Ataxia and upper respiratory tract stridor were significantly associated with plasma quinidine concentrations. In most instances (98%) conversion did not occur while toxic or adverse effects of quinidine sulfate were present or when plasma quinidine concentrations were > 5 μg/mL.     

Effects of oral powder electrolyte administration on packed cell volume,plasma chemistry parameters,and incidence of colic in horses participating in a 6-day 162-km trail ride

This study evaluated the effects of administering oral powder electrolytes on packed cell volume (PCV), plasma chemistry parameters, and incidence of colic in horses participating on a 6-day 162-km trail ride in which water was not offered ad libitum. Twenty-three horses received grain with powder electrolytes daily while 19 control horses received grain only. Horses were ridden approximately 32 km a day at a walk or trot. Packed cell volume and plasma chemistry parameters were analyzed daily. Episodes of colic were diagnosed and treated by a veterinarian unaware of treatment group allocation. Blood parameters and incidence of colic were compared between treatment groups. Electrolyte administration did not alter PCV or plasma chemistry parameters compared to controls. The incidence of colic was significantly higher in treated horses (P = 0.05). Oral powder electrolytes did not enhance hydration status or electrolyte homeostasis and may be associated with colic in horses participating on long distance trail rides similar to this model.     

Diagnostic Approaches for the Assessment of Equine Chronic Pulmonary Disorders

Even though the respiratory system is one of the most accessible organs for diagnostic testing, it is not always easy to define chronic lower airway disease in the horse. Diagnostic procedures performed by first opinion veterinarians in the field are often restricted to taking the history and performing clinical examination. Respiratory tract endoscopy, tracheal or bronchoalveolar lavage, and blood sampling are sometimes used but other specific ancillary examinations are seldom performed in stable settings. Therefore, our objectives were to evaluate the diagnostic value of different techniques and examination types routinely used in the diagnostic workup of chronic equine lower airway cases in both stable and clinical circumstances. Another aim of this study was to estimate the prevalence of different chronic pulmonary disorders among horses admitted to a Hungarian referral clinic. According to the conditional inference tree method, age of the horse, history, clinical examination, respiratory tract endoscopy, and bronchoalveolar lavage cytology proved to be the most valuable tools to define pathology. It was also concluded that in 22% of cases, more specific ancillary diagnostic modalities, unavailable for the field veterinarian, were needed to establish the final diagnosis. According to our study, the most frequently diagnosed chronic pulmonary disorders in Hungary are of noninfectious origin, principally recurrent airway obstruction. Regardless of the cause, and interestingly including recurrent airway obstruction as well, these diseases occur primarily during the warm months.     

Survey of Feeding Practices, Supplement Use, and Knowledge of Equine Nutrition among a Subpopulation of Horse Owners in New England

Nutrition is a critical component of equine health. Horse owners' knowledge of nutrition is likely to affect their feeding practices. The aim of this study was to survey feeding practices, dietary supplement use, and knowledge about equine nutrition in New England by surveying a subpopulation of horse owners (67/337 or 19.8%) who brought their horses to the Large Animal Hospital at the Cummings School of Veterinary Medicine at Tufts University between July and September 2008. All owners reported feeding hay, with the majority feeding grass or timothy hay. Most owners (96%) reported feeding a concentrate in addition to hay. Approximately 84% of owners reported including at least one dietary supplement in their horse's daily feeding. The most commonly used supplements were chondroprotectives, electrolytes, and multivitamins. Survey questions designed to assess the owner's knowledge of nutrition suggested that many owners may not have a basic understanding of principles of equine nutrition; less than 50% knew the daily water and hay requirements for a horse, and 69% lacked knowledge about the proper use of concentrates in a diet. Most of the surveyed owners consulted multiple sources of information concerning equine nutrition, including veterinarians (n = 36), trainers (n = 27), feed stores (n = 10), and the internet (n = 7). Although the major source of information was the veterinarian, it appears that the communication between horse owners and their veterinarian about optimal feeding practices could be enhanced. This survey demonstrated areas in the veterinarian–client dialog that need to be addressed when evaluating the health and well-being of the horse.     

Cortisol Circadian Rhythm Ratio: A Simple Method to Detect Stressed Horses at Higher Risk of Colic?

With the hypothesis that police horses with abnormal cortisol circadian rhythm (CCR) had more chance to develop colic, the aim of this study was to determine the CCR ratio in horses subjected to different housing and work conditions and to associate abnormal CCR ratio with incidence of colic. A total of 116 police horses belonging to four different groups were studied. In all, 31 were full-time stabled and performed urban patrolling activity, 27 were full-time stabled and performed equine therapy and sports activities, 25 were part-time stabled and performed urban patrolling, and 33 animals were kept full-time on pasture and did not perform any kind of work activity. Venous blood samples were collected between 6 and 7 am and also 8 hours later, and cortisol concentrations were determined by radioimmunoassay to calculate the CCR ratio. Annual colic incidences (6 months before and after the day on which CCR ratio was determined) were assessed by examining individual medical files. The overall incidence of abnormal CCR ratio (<0.30) was 63.3%, and 107 cases of colic were reported for this population with a mean incidence of 0.92 colic/horse/yr. Horses with abnormal CCR had 2.3 times more chance to have colic (95% CI: 1.07 to 5.28, P = .03) when compared with those with normal CCR. In conclusion, high incidence of abnormal CCR ratio indicates that police horses were under stressful conditions. Horses with abnormal CCR ratios were more prone to suffer colic episodes, indicating that CCR ratio determination could perhaps be useful in detecting horses at risk of colic.     

Use of newly developed assays for protein C and plasminogen in horses with signs of colic

Protein C content and plasminogen activity were measured in plasma from 100 horses with signs of colic. Data were analyzed by grouping horses 4 ways. Each horse was allotted to 1 of 2 outcome groups (survivors and nonsurvivors), 1 of 3 broad-category diagnosis groups (inflammatory disorders, strangulating obstructions, and all other gastrointestinal disorders), and 1 of 2 clinical management groups (medical and surgical). In a fourth grouping, all horses (although numbers of horses included in each subgroup were small) were assigned either to specific diagnostic groups that had high expectation for activated hemostasis (intestinal ischemia, endotoxemia, jugular thrombosis, peritoneal adhesions, and laminitis) or to a control group, in which active hemostasis was unlikely. Within 2 to 24 hours after admission, nonsurvivors developed lower protein C content than did survivors. Protein C content and plasminogen activity became low during hospitalization in horses with strangulating obstructions and in horses having surgery. The results from the grouping by specific diagnosis must be considered pilot data because the numbers of horses in each subgroup were small. Although not statistically significant, trends were noticed in protein C and plasminogen: (1) horses with intestinal ischemia and endotoxemia developed low protein C content and plasminogen activity, (2) protein C content became low in horses that developed peritoneal adhesions or laminitis, and (3) plasminogen activity became low in horses that developed jugular thrombosis. Low protein C content or low plasminogen activity, or both, may be useful as predictors for outcome and for these specific complications of equine colic.(ABSTRACT TRUNCATED AT 250 WORDS)     

Idiopathic muscular hypertrophy of the equine small intestine: 11 cases (1980-1991).

The medical records of 11 horses with idiopathic muscular hypertrophy (MH) of the small intestine were reviewed to determine the clinical and pathological features of the disease. The median age of affected horses was 10.0 years (range 5-18 years). No breed or sex predisposition was apparent. Ten horses (91%) had chronic (23 days to 2.4 years) signs of mild, intermittent colic, and 1 horse had signs of severe colic of only 3 days' duration. Partial anorexia and chronic weight loss of variable duration (1-6 months) were prominent historical findings in 5 (45%) horses. Diagnostic tests, with the exception of exploratory caeliotomy, were ineffective for definitive diagnosis of intestinal MH as a cause of colic. In 2 horses, however, a thickened, rigid ileum was detected by palpation per rectum, and in 5 horses, multiple loops of distended small intestine were detected by palpation per rectum. Hypertrophy of both the circular and longitudinal layers of muscularis was determined as the cause of intestinal thickening in all horses. Muscular hypertrophy of the ileum was present in 9 (82%) horses. Two horses (18%) had MH of a section of jejunum only, and 4 (36%) horses had MH of the ileum in combination with MH of other sections of small intestine. Two (18%) horses had MH of the entire small intestine. In 9 (82%) horses, intestinal MH resulted in narrowing of the luminal diameter at the site of MH. Small diverticula were present on the mesenteric border of the hypertrophied ileum of 5 (45%) horses. Five linear (up to 150-cm) diverticula were present in the hypertrophied jejunum of 1 (9%) horse. Haemomelasma ilei was present on the antimesenteric serosal surface of affected intestine of 8 (73%) horses. Full-thickness rupture of the ileum with subsequent diffuse, septic peritonitis occurred in 3 (27%) horses.