Physical activity, cardiovascular and biochemical changes of Chilean purebred horses to rodeo competitions

Abstract

A study, in order to characterize the level of physical work and the physiological and biochemical response of the Chilean purebred horse during the rodeo competition was carried out. Hippometric measurements of horses were taken and the weight of the rider, saddle and bridle were also determined. The perimeter of the rodeo track was measured in order to determine the work speed during the competition. Before and at different times after the first ride of a steer, the heart rate was recorded and blood samples were taken to measure packed cell volume (PCV), total proteins, haemoglobin, glucose, lactic acid, triglycerides, insulin, cortisol and the electrolytes: sodium, potassium, calcium and chloride. The plasma activity of the enzymes creatinekinase (CK), lactate dehydrogenase (LDH) and aspartate aminotransferase (AST) were also determined.

It is concluded that the Chilean purebred horse is characterized by a low height of withers, with a body length/heart girth ratio 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 Chilean horse carries out during the rodeo is to ride a 318 ± 11 kg body weight steer and to stop it in the track wall, carrying on its back a weight equivalent to 24% of its body weight, at speeds ranging between 5-8 m/s over a sand and circular track; exercise that determines significant increases in HR, PCV and in the plasma concentrations of haemoglobin, 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 exercise of force, speed and resistance which induces changes in their cardiovascular, hydrosaline, metabolic and endocrine activity, responses which are similar to those observed in high intensity exercises.