Original ResearchGender Differences–Induced Changes in Serum Hematologic and Biochemical Variables in Mangalarga Marchador Horses After a Marcha Gait Competition
Introduction
With its distinctive and comfortable lateral and diagonal gait, the Mangalarga Marchador horse is one of the most important breeds in Brazil. This breed is used for a specific functional trial called the marcha competition. Characterized by long duration and high metabolic demand, marcha competition is carried out in circles, at constant speed without interruption during the events [1].
It has been shown that physical exercise induces physiological responses to meet increasing metabolic requirements during activities [2]. So, understanding these responses and identifying the behavior of hematological parameters during physical exertion are essential elements in the evaluation of competition horses [3]. In an attempt to evaluate performance and evaluate fitness, a considerable number of studies have been carried out to investigate the physiological response of horses to different exercise types [4].
Arabian breed horses that performed the Standard Incremental Exercise Test exhibited high serum levels of the enzymes aspartate aminotransferase (AST), creatine kinase (CK), and lactate dehydrogenase (LDH) [5]. Similar results were obtained for the Crioulo breed during adaptation to exercise [6]. Likewise, potassium serum levels increased in Quarter horses after team roping [7], and important physical, biochemical, and hematologic changes were observed in horses after cattle roundups in rodeo competitions [8]. Such findings have been associated with exercise-induced responses in addition to the lack of proper training routines and the unfavorable conditions sometimes observed in rodeo events. Also, Santiago et al. [9] observed increased lactate metabolism in horses after eventing competitions, and Miranda et al. [10] reported high levels of mean hemoglobin, erythrocytes, and leukocytes in horses after team penning.
Studies with Mangalarga Marchador horses after marcha gait have revealed that exercise alters levels of lactate [11] and of insulin and cortisol [12]. However, no research has been carried out under actual competition conditions to investigate how these parameters behave. In this scenario and considering the increasing popularity of marcha gait, the aim of this study was to investigate whether marcha exercise results in changes in serum hematologic and biochemical variables and whether this condition differs in male and female Mangalarga Marchador horses.
Section snippets
Horses and Sompetition
This study was approved by the ethics committee on animal experiments of Universidade Estadual do Norte Fluminense Darcy Ribeiro (CEUA/UENF), under protocol number 2014-250. Evaluations were carried out during a marcha gait in a rodeo park in the city of Campos dos Goytacazes, Rio de Janeiro, Brazil (south latitude 20°48′21″, west longitude 40°38′52″, and altitude 13 m). Mean temperature was 24°C, and relative humidity was 80%.
Thirty-five Mangalarga Marchador horses, 18 males and 17 females,
Results
In both males and females, RBC, HCT, AST, and GGT activity increased in response to exercise, but there were no significant differences between the genders. In females, significant increases in total protein, BUN, creatinine, CK, and LDH levels were detected after the marcha gait (T1), but no such changes were detected in males.
Total WBC concentrations increased in response to the exercise in both males and females, but there were no differences between the genders (Table 1). Plasma hemoglobin,
Discussion
The changes observed in hematological parameters were due to the decrease in plasma volume caused by respiration, redistribution of vascular volume, loss of fluids through sweating, and splenic contraction [4]. In horses, splenic contraction increases erythrocyte levels by up to 40%, stimulating blood oxygenation competence [14]. Contraction of splenic muscles takes place as a response to sympathetic stimulus prompted by exercise through an adrenergic mechanism [3]. This releases large amount
Conclusion
Marcha exercise–induced dehydration, observed as an increase in hematocrit, red blood cells, and total protein levels. Also, exercise influenced the metabolic requirements, represented by higher protein catabolism levels and increased muscle cell permeability, as reflected by the rise in serum levels of AST, CK, and LDH. Changes were also observed in white blood cell counts, characterizing marcha gait as a stressful exercise mode to Mangalarga Marchador horses.
The results of the present study
Acknowledgments
The authors declare no competing interests. None of the authors has any financial or personal relationships with other people or organizations that could inappropriately influence or be perceived to influence the content of the article.
Authors' contributions: P.A.D.F. and F.A.S.G. participated in the design of the study, supervised the experiments, revised, and submitted the final article. L.P.M., S.T.L., and R.M.S.P. participated in the study from the early phase up to the end of data
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