CLINICOPATHOLOGICAL COMPARISON BETWEEN TWO DIFFERENT HIGH SPEED - SHORT TERM COMPETITIONS IN RACEHORSES

In human sport medicine, clinicopathological abnormalities are frequently detected in response to different training periods or competitions. Similar findings are described in equine medicine especially for plasmatic muscular enzymes (PMEs), oxidative stress markers and erythrocyte alterations, however their significance related to the performance is still unclear. The aim of this study was to compare clinicopathological data obtained from horses entered at 2 different high speed – short term real competitions. The first group (G1) included 34 Standardbred racing horses performing a trotting race for a total distance of 1660 m in about 2 minutes. The second group (G2) comprised 10 Thoroughbred horses involved in a galloping race, consisting in repetitive tracks of 154 m each in about 12 seconds. Blood samples were obtained before and after the races. CBC, biochemical and haemostatic parameters including PMEs (Creatine Kinase – CK; Lactate Dehydrogenase – LDH; Aspartate Transaminase – AST) Uric Acid (UA), Haptoglobin (Hp), Fibrinogen (Fib) and D-Dimer (DD), were evaluated. DD and Hp were assayed with immuno-turbidimetric methods. The post exercise data were corrected using an estimation of the plasma volume contraction according to the individual Albumin (Alb) concentration increment. The variation of each parameter was compared within- and between-races. The statistical analyses were carried out using non parametric tests for data within- and between-groups. A difference was considered significant at p<0.05. A significant plasma volume contraction after the race was evidenced in both groups (Alb: G1 +6.86%; G2 +9.07%). Other relevant findings induced by the competition were the increased concentrations of PMEs (CK: G1 +123.1%; G2 + 273%; LDH: G1 +54.2 %; G2 +27%) and Uric Acid (G1 +227%; G2 +958%) indicative of muscular damage and oxidative stress, respectively. A significant reduction of Hp was documented in both groups (G1 -8.7%; G2 -24%), suggesting an intravascular haemolysis associated to the competition. A state of hypercoagulation and hyperfibrinolysis were also suggested by the detection of a significant plasmatic DD concentration increase (G1 +22.8%; G2 +23%) and Fib decrease (G1 -3.71%; G2 -12%) post-race. G2 presented more significant alterations in the clinicopathological variables investigated, including an higher CK and DD concentration increment, and Hp and Fib reduction. Our results suggest that high speed - short term competitions produce relevant abnormalities on clinical pathology. Particularly, strenuous galloping racehorses seems to be at major risk of organic injury. Further studies on larger cohort of animals are needed to understand pathogenesis and clinical relevance of these alterations in equine medicine.