¹Istanbul University, Vocational School of Veterinary Medicine, Equine and Equine Training Programme, TR-34320 Avcilar, İstanbul - TURKEY DOI : 10.9775/kvfd.2017.18674 The aim of this study is to evaluate physical, haematological and biochemical changes in horses after acute exercise in a jereed game. Jereed is a traditional Turkish equestrian team sport. A total of 14 horses were included in this study. All horses were Arabian stallions aged between 4-14 years old. Respiration rate, heart rate, capillary refill time, mucous membrane and skin turgor (as an indicator for dehydration) were measured and blood samples were collected before the exercise (T0), immediately after first period (T1) and second period (T2), after 30 min (T3) and 60 min of recovery time (T4). Blood samples were analyzed for total cell counts and for determination of lactate, glucose, urea, total protein, albumin, globulin, calcium, magnesium, phosphorous, chloride, sodium, potassium, creatinine kinase, lactate dehydrogenase, aspartate aminotransferase and alkaline phospahatase. All parameters were analyzed using Linear Mixed effect model to evaluate changes of repeated measurements at 5 different time points and LSD was used as post-hoc test. Exercise caused significant increases in heart rate (P<0.001), respiratory rate (P<0.001), capillary refill time (P<0.001), mucous membrane colour (P<0.001), dehydration (P<0.001), red blood cells (P<0.001), hemoglobin (P<0.001), hematocrit (P<0.001), red cell dispersion width (P<0.001), total white blood cells (P<0.001), neutrophils (P<0.001), and basophils (P<0.05). It also caused significant increases in lactate (P<0.01), glucose (P<0.001), urea (P<0.001), total protein (P<0.001), albumin (P<0.001), globulin (P<0.001), sodium (P<0.001), potassium (P<0.001), creatinine kinase (P<0.05), lactate dehydrogenase (P<0.001), aspartate aminotransferase (P<0.001) and alkaline phosphatase (P<0.001) but a decrease in calcium (P<0.01), magnesium (P<0.01), phosphorous (P<0.05), and chloride (P<0.001). Although majority did not return to the baseline 30 or 60 minutes after competition (P<0.05) most were within or near to the reference range values. Keywords : Jeered, Horse, Exercise, Haematology, Biochemistry