Horses with colon torsion require immediate surgery in order to ensure survival of the compromised intestine and the horse. Intestinal inflammation in horses has been shown to cause changes in serum and peritoneal fluid concentrations of serum amyloid A (SAA) and haptoglobin, but there is a lack of information regarding this during early phases of intestinal vascular compromise and inflammation. The aim of this study was to evaluate serum concentrations of SAA and haptoglobin in response to experimentally induced ischemia and reperfusion of the equine colon. Colon ischemia (1hour) and reperfusion (4 hours) were induced by ligation and subsequent release of the ligature of the pelvic flexure in 5 horses under general anesthesia. Jugular venous blood samples were collected before ischemia (T0) and after ischemia (T1), and after1 hour (T2) and 4 hours of reperfusion (T3). Serum haptoglobin decreased significantly (p=0.002) from a mean concentration of 1555 mg/L (T0) to 1200 mg/L (T3), whereas concentrations of SAA did not change significantly. The results suggest that a decrease in serum haptoglobin occurs in the early phase of intestinal ischemia and inflammation. The decrease in haptoglobin concentrations may have been caused by local haemolysis induced by vascular compromise, as haptoglobin is known to bind free haemoglobin. This knowledge can be useful when evaluating the severity of the intestinal and vascular damage in horses with colon torsion. But further studies are needed to understand the pathogenesis of the observed haptoglobin response during colonic ischemia and reperfusion.