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.

Background: The prevalence of obesity in horses in the eastern United States is not well documented. Objective: To determine body condition and risk factors for obesity in horses in Southwest Virginia during summer. Animals: A sample of 300 mature (4-20 years old), light breed horses (140 mares, 151 geldings, and 9 stallions) from the VMRCVM Equine Field Service practice equine database. The horses were from 114 farms and 138 owners.Methods: Horses were evaluated over a 60-day period in this cross-sectional, prospective study. A questionnaire was completed for each horse. Body condition score (BCS) was assigned using a scale of 1 (emaciated) to 9 (obese) by 2 independent scorers. Morphometric measurements included average neck circumference (ANC), girth, body length, and height at the withers. Horses were categorized based on BCS as underconditioned (BCS < 4), optimal condition (BCS 4-6), overconditioned (BCS 7), and obese condition .Results: Five horses (1.7%) were underconditioned, 142 horses (47.3%) were optimally conditioned, 97 horses (32.3%) were overconditioned, and 56 (18.7%) were obese. Estimated body weight (EBW) (r = 0.14, P = .015), body mass index (BMI) (r = 0.46, P < .001), and neck circumference to height ratio (NCHR) (r = 0.50, P = .001) increased with increasing BCS.Conclusions and Clinical Importance: The prevalence of overconditioned and obese horses in this population was higher than reported in previous studies and indicates that obesity might be an emerging problem in horses.