ABSTRACT. Abramovitc G., Parra A.C. & Fernandes W.R. [Changes in iron levels, total iron binding capacity, transferrin saturation in race horses, before and after of physical exercise]. Variação de níveis séricos de ferro, da capacidade total de ligação do ferro e da saturação da transferrina em equinos de corrida, antes e após exercício físico. Revista Brasileira de Medicina Veterinária, 36(3):289-293, 2014. Departamento de Clínica Médica, Faculdade de Medicina Veterinária e Zootecnia, Universidade de São Paulo, Rua Prof. Dr. Orlando Marques de Paiva 87, Cidade Universitária, Butantã, São Paulo, SP 05508-270, Brasil. Email: firstname.lastname@example.org The preparation of the horse for physical activities in competition is directly related to important factors such as nutrition, muscle adaptation and blood profile, related to the concentration of serum iron, total capacity total iron binding capacity (TIBC) and saturation of transferrin. This study aimed to evaluate the influence of exercise in iron levels, the total iron and transferrin saturation in race horses. One hundred and eleven samples of blood serum were collected from Thoroughbred horses, from the Jockey Club of São Paulo, aged between 3 and 4 years old, male and female, clinically healthy, practitioners turf competition, in sand or grass. The samples were obtained before exercise (control time) and 30 minutes after exercise (post exercise). These animals were submitted to gallop training, of high intensity and short duration for this research. As a result, it was observed that the serum concentration of iron (Fe) showed a statistically significant lowering post-exercise, due to organic re-balance of iron, while TIBC (total iron binding capacity) showed a clear and significant increase in their serum levels due to increased needs of iron during and after exercise. The percentage of transferrin saturation in serum was shown to be lower post-exercise, probably due to the recruitment of iron ion in the acute phase inflammatory reaction that may occur during the exercise by cellular suffering and stress. It is concluded that the exercise performed by the evaluated horses had significant influence on the basic needs of serum iron, total iron binding capacity and the percentage of transferrin saturation of equine athletes.