Abstract: Background – Hypovitaminosis D is associated with mortality in critically ill foals. Vitamin D concentrations [VitD] in horses with colitis has not yet been studied. Objectives – Determine the [VitD] in healthy horses and horses with colitis and their association with mortality and the severity of the disease. Animals – Twenty-five healthy and eighty-nine horses with colitis. Methods – Prospective case-control study. Serum [VitD] were measured on admission in horses with colitis. Survival was determined by hospital discharge. Horses were classified as SIRS and non-SIRS based on alterations in body temperature, heart and respiratory rate, and total white blood cells. Blood concentration of creatinine was also recorded on admission. Data was analyzed by non-parametric methods. Results – [VitD] were not statistically different between healthy (9.7 ng/ml [4.9-29.6]) and horses with colitis (10.3 ng/ml [3.5-31.3]) (p=0.96). In horses with colitis, [VitD] were not different between survivors and non-survivors (10.4 ng/ml [4.5-31.3] vs 10.0 ng/ml [3.5-20.9], p=0.98). Horses with colitis that had SIRS and azotemia (creatinine >130 umol/L) had significantly lower [VitD] (9.7 ng/ml [3.5-17.0]) than those without SIRS and azotemia (10.8 ng/ml [4.5-31.3]) (p < 0.05). The survival proportion of horses with colitis, SIRS and azotemia was lower than horses with colitis without these alterations (p=0.04). Conclusions and clinical importance –There were no statistical differences in [VitD] between healthy and horses with colitis. However, horses with colitis with systemic inflammation and volume depletion tend to have lower [VitD] and are less likely to survive.
