A surprisingly large number of horses in a British study investigating colic in the large colon were not ridden, the researchers found.
“This trend has not been reported previously, and warrants further research to determine whether this is a significant risk factor,” said the University of Nottingham researchers, whose findings have been published in the journal, BMC Veterinary Research.
The researchers, Kyra Megan Jennings, Laila Curtis, John Harold Burford and Sarah Louise Freeman, all from the university’s School of Veterinary Medicine and Science, centred their research on reports from British veterinarians on their front-line treatment of 120 cases of colic in the large colon.
They said their findings, along with evidence from previous studies on the effects of exercise and the increased risk associated with box rest, suggest that activity levels may be an important factor in the origins of large colon impactions in horses.
Their research, which represents the first study of the primary presentation of large colon impactions in Britain, paints a picture of how cases present and are initially assessed and treated by vets.
Jennings and her colleagues said large colon impactions were a common cause of colic in horses.
However, current published evidence on risk factors, clinical presentation and decision-making in large colon impaction cases was based on cases referred to hospitals, which represented a particular section of the case population.
There was a lack of evidence from front-line practices on the wider equine population, and on how large colon impaction cases initially present to vets, they said.
The researchers set out to describe the initial clinical presentation, diagnostic approach and treatment at veterinarians’ initial assessment of horses with large colon impactions, based on case-record data from vets gathered over 12 months from October 2012.
To meet the researchers’ criteria, cases had to be diagnosed as a primary large colon impaction with positive findings on rectal examination. Case outcomes were categorised into three groups: simple medical (resolved with a single treatment), complicated medical (resolved with multiple medical treatments) and critical (animals that required surgery, were euthanised or died).
In all, they received information on 1032 colics, 120 of which met their inclusion criteria for large colon impaction.
They found 53 percent were categorised as simple medical, 36.6 percent as complicated medical, and 9.2 percent as critical. The critical cases totalled 11. Seven of the animals were euthanized, three died, and one required surgery.
Most cases (42.1 percent) occurred during winter.
They found that 59 percent of horses had experienced a recent change in management.
Analysis showed 43 percent of the horses were not ridden, and 12.5 percent had a recent or current musculoskeletal injury.
The mean heart rate across the cases was 43 beats per minute (bpm), ranging from 26 to 88 bpm.
Most cases showed mild signs of pain (67.5 percent) and reduced gut sounds (76 percent).
Heart rate tended to be much faster and gut sounds significantly decreased in critical cases compared to those classified as simple medical colics.
They found that 50 different treatment combinations were used, with non-steroidal anti-inflammatory drugs (NSAIDs) used in 93 percent of cases and oral fluids given in 71 percent of cases.
They concluded that large colon impactions typically presented with mild signs of colic; heart rate and gut sounds were the most useful parameters to distinguish between simple and critical cases at the primary assessment.
The researchers said their findings of seasonal incidence and associated management factors were consistent with other studies.
Vets, they noted, currently used a wide range of different treatment combinations for large colon impactions.
The horses in the study comprised 39 of hotblooded breeding, 39 warmbloods, 25 ponies, and 14 heavy horses. The other three were not recorded. There were 60 geldings and 60 mares.
The age of the horses ranged from 3 to 41 years, with the median being 10.
They found evidence of an association between sex and outcome, with fewer mares having complicated medical or critical outcomes.
No statistically significant differences in breed, age or body condition between the different outcomes were found.
Thirty nine of the 120 cases (32.5 percent) were reported to have had previous or concurrent health problems. Five of these had more than one health problem. The most common problems were a current or recent musculoskeletal injury, a previous colic episode, or a chronic or old musculoskeletal injury.
The frequency of ridden exercise was recorded in 118 cases: 51 (43.2 percent) of the horses were not ridden at all, 23 (19.5 percent) were ridden 1-2 times a week, 36 (30.5 percent) were ridden 3-6 times a week, and 8 (6.8 percent) were ridden daily.
Information was provided on the type of feed given the horses in 104 cases: 77 horses (74 percent) were fed hay, 32 (30.8 percent) were fed horsehage, two (1.9 percent) were fed straw, and 54 (51.9 percent) received concentrates.
From 50 responses concerning housing, 20 horses (40 percent) were kept at grass, 17 (34 percent) were stabled and 13 (26 percent) were stabled and turned out.
Ninety-seven case forms provided information on changes in management. Of these, 57 horses (59 percent) had experienced a change in management before the colic episode, and the most common changes centred on diet, box rest and increased stabling.
There was a variation in the incidence of cases in each season, with the largest number of cases (41.2 percent) occurring during winter. Thirty three cases (27.7 percent) occurred in spring, 12 cases (10.1 percent) in summer and 25 cases (21 percent) in autumn.
Changes in management occurred more frequently during the winter, they noted, but there was no significant difference in the number of management changes between the seasons.
Using a pain severity scoring system, four horses (3.3 percent) were reported as having no signs of pain, 81 (67.5 percent) had mild signs of pain, 31 (25.8 percent) had moderate signs of pain, and four (3.3 percent) had severe signs of pain on initial presentation.
There was no evidence of a difference in respiration rate or rectal temperature based on the assessed severity of the cases.
The main treatment types given were NSAIDs, given to 111 horses. Oral fluids were given to 84 horses, while 66 received muscle relaxants. Sedatives were used on 52 horses, laxatives on 29 horses, opioids on 18, electrolytes on 8, and intravenous fluids on 5. Other treatments were used on seven horses, and included worming medications, tetanus antitoxin, steroids, controlled feeding, and walking out.
Flunixin was the most frequently used NSAID (in 42.7 percent of cases), followed by phenylbutazone (33.6 percent). Detomidine was the most frequently used sedative, in 49 percent of cases, followed by xylazine in 38.8 percent of cases and romifidine in 12.2 percent of cases.
Hyoscine was the only muscle relaxant used.
Complicated medical cases and critical cases were significantly more likely to receive intravenous fluids during the first visit.
A total of 50 different combinations of treatments were used at the primary case presentation. This, they said, was mainly due to the range of different drugs and treatments available.
“Recent evidence has demonstrated the efficacy of oral fluids for rehydrating ingesta and resolving impactions,” the researchers noted.
Laxatives, intravenous fluids, opioids and electrolytes were seldom used on the primary assessment. “This may reflect the influence of recent research on veterinary practitioners’ choice of treatments, but may also reflect a decision to use less expensive treatments - oral versus intravenous fluids – at the initial presentation,” they suggested.
“The large range of different treatment combinations used to treat the 120 cases in this study highlights the variation between veterinary practitioners in their treatment approach.
“The current existing evidence on treatment is based on experimental studies and referral hospital case populations, and this study highlights the need for evidence generated by and targeted at front-line practitioners.”
Jennings and her colleagues said several findings from the study were in agreement with previous studies on impactions in horses referred to hospital for treatment and on non-specific colic cases in the general population.
These included the recent changes in diet, an increase in stabling and box rest, and seasonal variation.
The surprisingly large number of horses in the study that were not ridden was a trend that had not been reported previously, they said, adding that it warranted further research to determine whether it was a major risk factor.
Prospective survey of veterinary practitioners’ primary assessment of equine colic: clinical features, diagnoses, and treatment of 120 cases of large colon impaction.
Kyra Megan Jennings, Laila Curtis, John Harold Burford and Sarah Louise Freeman.
BMC Veterinary Research 2014, 10(Suppl 1):S2 doi:10.1186/1746-6148-10-S1-S2
The full study can be read here.