PHYSICAL-ACTIVITY, CARDIOVASCULAR AND BIO CHEMICAL-CHANGES OF CHILEANPUREBRED HORSES TO RODEO COMPETITIONS

A study, in order to characterize the level of physical work and the p hysiological and biochemical response of the Chilean purebred horse du ring the rodeo competition was carried out. Hippometric measurements o f horses were taken and the weight of the rider, saddle and bridle wer e also determined. The perimeter of the rodeo track was measured in or der to determine the work speed during the competition. Before and at different times after the first ride of a steer, the heart rate was re corded and blood samples were taken to measure packed cell volume (PCV ), total proteins, haemoglobin, glucose, lactic acid, triglycerides, i nsulin, cortisol and the electrolytes: sodium, potassium, calcium and chloride. The plasma activity of the enzymes creatinekinase (CK), lact ate dehydrogenase (LDH) and aspartate aminotransferase (AST) were also determined. It is concluded that the Chilean purebred horse is charac terized by a low height of withers, with a body length/heart girth rat io that agrees with a medium size horse of 392 +/- 33 kg body weight. These characteristics match those described in the standard values for the Chilean criollo horse. The principal physical activity that the C hilean horse carries out during the rodeo is to ride a 318 +/- 11 kg b ody weight steer and to stop it in the track wall, carrying on its bac k a weight equivalent to 24% of its body weight, at speeds ranging bet ween 5-8 m/s over a sand and circular track; exercise that determines significant increases in HR, PCV and in the plasma concentrations of h aemoglobin, glucose, lactic acid, triglycerides, insulin, cortisol and in the serum activity of enzymes CK, LDH and AST. Increases in total serum proteins and a delayed decrease in serum potassium concentration were the most significant changes observed in the hydrosaline balance . It is concluded that for Chilean horses, the rodeo represents an exe rcise of force, speed and resistance which induces changes in their ca rdiovascular, hydrosaline, metabolic and endocrine activity, responses which are similar to those observed in high intensity exercises.