Creatine Kinase (CK), Aspartate Aminotransferase (AST) and Lactic Dehidrogenase (LDH) concentration was determined in serum samples obtained from 60 horses of the Criollo breed: 20 mares managed on pasture (Group A), 20 horses in training (Group B) and 20 horses participating of the Freio de Ouro 1997 competition (Group C), where samples were collected 24-48 hours before competition and 24 and 48 hours there after. There was no difference in LDH values between groups. Group B horses had higher (p<0.05) CK and AST serum concentrations than horses in groups A and C, indicating an adaptation to exercise. Forty eight hours after competition, CK values were lowest and AST highest. CK and AST were more informative than LDH in evaluating muscular function. Females had higher CK activity (p<0.05) than males. There were significam diferences related to final outcome of competition with a trena of lower values in the first places, indicating the athletic condition of the best horses.
CK; AST; LDH; horses
