Summary A prospective study of one year was conducted on 31 horse farms to obtain population based estimates of incidence, morbidity and mortality rates of equine colic. Farms with greater than 20 horses were enrolled by randomly selecting horse owners from 2 adjacent counties of Virginia and Maryland. Descriptive information for 1427 horses was collected at the initiation of the study and updated at 3 month intervals. Time on the farm during the study was tabulated for each horse. When colic was reported by the owner, investigators visited the farm to obtain information about the colic. The crude incidence density rate of colic was 10.6 colic cases/100 horse‐years, based on 104 cases/358,991 horse‐days. The median farm specific incidence density rate was 7 cases/100 horse‐years, and the range for individual farms varied from 0 to 30 colic cases/100 horse‐years. A specific diagnosis was not made for 84 (81%) of colic episodes. Seventy colic episodes (67%) were treated by a veterinarian. Drugs were used in 83 (80%) colic episodes, and 78 (75%) of colic cases were mild, requiring no treatment or resolving after only one treatment. Four horses required colic surgery. Fourteen (13%) horses had more than one episode of colic during the year. Mortality from all causes of death was 2.5 deaths/100 horse‐years, mortality rate for colic was 0.7 deaths/100 horse‐years. Proportional mortality rate of colic, 28%, was higher than for any other cause of death. Horses less than age 2 years or greater than age 10 years had lower incidence than horses age 2–10 years. No difference in colic risk between genders was identified. Arabian horses had the lowest and Thoroughbreds the highest breed specific incidence rates. Horses used for eventing, or in training had a statistically significant higher incidence rate of colic compared to mature horses with no use (pets, retired, on pasture with no stated purpose). Horses used for lessons or with no use had the lowest incidence rates.

Summary A1 year prospective study was conducted on 31 horse farms to identify risk factors for equine colic. Farms were randomly selected from a list from 2 adjacent counties of Virginia and Maryland, USA. The association between colic and farm or individual horse risk factors related to management, housing, pasture, use, nutrition, health and events was first examined by univariate statistical analysis. Individually significant (P<=0.25 for farm factors, P<=0.10 for horse factors) variables were used in a stepwise multivariable forward logistic regression to select explanatory factors (P<=0.05). Analysis was conducted at 2 levels: farm and individual horse with farm specified as a random effects variable. No farm‐level variables were significant Significant horse‐level variables included: age, odds ratio (OR)=2.8 for horses age 2–10 years compared to <2 years; history of previous colic, OR=3.6 relative to no colic; changes in concentrate feeding during the year (1 per year, OR=3.6, more than 1, OR=2.2) relative to no changes; more than 1 change in hay feeding during the year, OR=2.1 relative to no changes; feeding high levels of concentrate (>2.5 kg/day dry matter, OR=4.8, >5 kg/day dry matter, OR=6.3) relative to feeding no concentrate; and vaccination with monocytic ehrlichiosis vaccine during the study, OR=2.0 relative to no vaccination. Feeding a whole grain with or without other concentrate components reduced risk, OR=0.4, relative to feeding no whole grain. Results of the study suggest that diet and changes in diet are important risks for colic in a population of horses on farms.

The national impact of equine colic is substantial because of the high case fatality rate.

Results suggested that various factors were associated with outcome in horses with septic tenosynovitis. However, surgical technique was not found to be associated with survival rate or rate of return to intended use.

Thirty-two physical examination and laboratory variables were recorded during examination of 165 horses admitted for acute abdominal disease. Univariate analyses were performed to determine which of the variables were significantly different between horses that lived or died. Stepwise logistic regression was performed to identify variables with the best predictive value. Four variables (heart rate, peritoneal fluid total protein concentration, blood lactate concentration, and abnormal mucous membrane) remained significant when entered into the model. Histograms for each significant variable were used to set "cutting-points," establishing categories that were made into a table of assigned values from which a Colic Severity Score (CSS) for each horse was calculated. Seventy-one horses in a second group were used to validate the scoring chart. Case mortality rate was similar in both groups (20.6% in development group versus 21.1% in validation group). All horses with a CSS > 7 died, whereas 75% of those with a score of < or = 7 lived. For the validation group, use of the scoring table yielded a positive predictive value of 100%, negative predictive value of 91.8%, sensitivity of 66.7%, and specificity of 100%. The overall accuracy of the CSS was 93%. The CSS is a rapid and accurate method for predicting survival in cases of equine acute abdominal disease.

Summary Although large intestine impactions are commonly treated with i.v. fluids combined with the osmotic laxative MgSO4, enteral fluids are less expensive and also appear to be efficacious for impactions. Therefore, this study was conducted to compare the systemic and gastrointestinal effects of enteral fluids with the changes produced by i.v. fluids combined with MgSO4. Four horses with a fistula in the right dorsal colon alternately received both treatments in 2 periods one week apart. Sixty litres of fluids were administered continuously (10 l/h) through a venous catheter or a nasogastric tube. Magnesium sulphate (1 g/kg bwt) was administered via nasogastric tube before i.v. fluid therapy. Two horses had mild abdominal discomfort at the end of enteral fluid therapy. Pollakiuria, hypostenuria, increased bodyweight, increased faecal and ingesta hydration, and decreased PCV, plasma protein and plasma magnesium were produced by both treatments. Abdominal distention and more pronounced changes in bodyweight and ingesta hydration were seen with enteral fluids. Intravenous fluids plus MgSO4 produced hypocalcaemia and more pronounced changes in plasma protein. These results indicate that enteral fluid therapy is more effective in promoting ingesta hydration and produces less pronounced systemic effects than i.v. fluid therapy plus MgSO4.

This study provides the first report of the bioavailability of orally administered GL and LMWCS in the horse.

Horses with multiple foot lesions managed with conservative therapy have a guarded prognosis for long-term soundness. Deep digital flexor tendinopathies negatively influence prognosis.