Alterações séricas de proteína total e eletrólitos em cavalo Pantaneiro durante exercício de longa distância

Serum electrolyte and total protein alterations in Pantaneiro horse during long distance exercise

Resumos

Foram colhidas amostras de sangue de oito cavalos Pantaneiro durante uma prova de resistência de 76km através do Pantanal. Um mês antes da prova os cavalos foram distribuídos em dois grupos: 1- quatro cavalos mantidos em pastagem nativa sem suplementação e sem trabalho; 2- quatro cavalos mantidos em pastagem nativa com suplementação e submetidos a trabalho. Amostras de sangue foram colhidas antes da prova (pré), durante (meio), ao final (pós) e após um período de recuperação de 30 minutos (descanso). Foram analisadas as concentrações séricas de proteína total (PT), albumina (Alb), sódio (Na), potássio (K), cloro (Cl), cálcio (Ca) e fósforo (P). No final da prova também foram colhidas amostras de suor de cinco cavalos para análise de Na, K e Cl. Durante a prova, houve diminuição significativa nos teores de Ca e K e aumento nos teores de Na e P em ambos os grupos. Os valores médios da taxa cardíaca após 30 minutos de descanso indicaram boa resposta de recuperação.

Cavalo Pantaneiro; prova de resistência; taxa cardíaca; eletrólito; proteína


Blood samples were taken from eight Pantaneiro horses during a 76km endurance ride. The horses were divided into two groups: 1- four horses kept on native pasture, without working and with no supplementation during one month before the ride, 2- four horses kept on native pasture with supplementation and submitted to work during one month before the ride. Serum concentration of total protein, albumin, sodium, potassium, chloride, calcium and phosphorus were measured. Samples were taken before the ride (preride), during the mid point (midride), at the end of the ride (postride) and after a 30-minute recovery period (rest). Sweat samples were collected from five horses at the end of the ride to measure sodium, potassium, and chloride. In both groups, there was a significant decrease in calcium and potassium, and an increase in sodium and phosphorus during the ride. Heart rate values after 30 minutes of rest indicated a good recovery response.

Horse; Pantaneiro breed; endurance ride; heart rate; electrolyte; protein


Serum electrolyte and total protein alterations in Pantaneiro horse during long distance exercise

[Alterações séricas de proteína total e eletrólitos em cavalo Pantaneiro durante exercício de longa distância]

S.A. Santos1, R.A.M.S. Silva1, J.R.M. Azevedo2, M.A.R. Mello2, A.C. Soares3, C.Y. Sibuya2, C.A. Anaruma2

1Centro de Pesquisa Agropecuária do Pantanal – CPAP-EMBRAPA

Rua 21 de Setembro, 1880 - Bairro Nossa Senhora de Fátima

79320-900 - Corumbá, MS

2Instituto de Biociências, UNESP - Rio Claro, SP.

3Bolsista da Rhae/CNPq

Recebido para publicação, após modificações, em 23 de janeiro de 2001

ABSTRACT

Blood samples were taken from eight Pantaneiro horses during a 76km endurance ride. The horses were divided into two groups: 1- four horses kept on native pasture, without working and with no supplementation during one month before the ride, 2- four horses kept on native pasture with supplementation and submitted to work during one month before the ride. Serum concentration of total protein, albumin, sodium, potassium, chloride, calcium and phosphorus were measured. Samples were taken before the ride (preride), during the mid point (midride), at the end of the ride (postride) and after a 30-minute recovery period (rest). Sweat samples were collected from five horses at the end of the ride to measure sodium, potassium, and chloride. In both groups, there was a significant decrease in calcium and potassium, and an increase in sodium and phosphorus during the ride. Heart rate values after 30 minutes of rest indicated a good recovery response.

Keywords: Horse, Pantaneiro breed, endurance ride, heart rate, electrolyte, protein

RESUMO

Foram colhidas amostras de sangue de oito cavalos Pantaneiro durante uma prova de resistência de 76km através do Pantanal. Um mês antes da prova os cavalos foram distribuídos em dois grupos: 1- quatro cavalos mantidos em pastagem nativa sem suplementação e sem trabalho; 2- quatro cavalos mantidos em pastagem nativa com suplementação e submetidos a trabalho. Amostras de sangue foram colhidas antes da prova (pré), durante (meio), ao final (pós) e após um período de recuperação de 30 minutos (descanso). Foram analisadas as concentrações séricas de proteína total (PT), albumina (Alb), sódio (Na), potássio (K), cloro (Cl), cálcio (Ca) e fósforo (P). No final da prova também foram colhidas amostras de suor de cinco cavalos para análise de Na, K e Cl. Durante a prova, houve diminuição significativa nos teores de Ca e K e aumento nos teores de Na e P em ambos os grupos. Os valores médios da taxa cardíaca após 30 minutos de descanso indicaram boa resposta de recuperação.

Palavras-chaves: Cavalo Pantaneiro, prova de resistência, taxa cardíaca, eletrólito, proteína

INTRODUCTION

The Pantanal is a vast floodplain in the centerwest region of Brazil, and it is characterized by rainy and dry seasons. The intensity of flooding depends on rainfall, which presents multiyear cycles of greater or lesser intensity (Adámoli, 1987). In this region, beef cattle raising is the main economic source of income. Pantaneiro horses are adapted to the bioclimatic conditions of this region, constituting an important economic and social factor, essential for the cattle industry and for regional transportation (Santos et al., 1992).

Farms consist of vast extent of land and horses ride long distances during periods of high temperature on swampy and sandy terrain. Long distance and exercise impose great physiological demands on horses (McConaghy, 1994). During exercise electrolyte loss in sweat depends on ambient temperature and humidity. The most extreme sweat loss is found during hot and humid conditions. Alterations in electrolyte concentrations could seriously affect working or athletic performance (Rose & Hodgson, 1994; Evans et al., 1995). Thus, modification of thermoregulatory responses to exercise as a result of training is probably very important (Rose, 1986).

The adaptive mechanisms to hyperthermia and possible effects of acclimatization have not been studied intensively in horses (Rose, 1986), especially in native (local) breeds that have been subjected to an adaptation process due to environmental conditions similar to Pantaneiro horse in the Pantanal. This paper examines some serum and sweat electrolytes, and serum total protein and albumin changes in Pantaneiro horses during a 76km endurance ride through Pantanal.

MATERIALS AND METHODS

Horses included in this study were approximately six-year-old and had been used for guiding cattle since they were three-year-old. Eight castrated Pantaneiro horses, divided into two groups, were used during a 76km endurance ride. In group 1, four horses, with 350-360kg of body weight were kept on native pastures, without working and not supplemented for one month before the ride. In group 2, four horses, with 345-356kg of body weight were kept on native pastures, supplemented with maize comprising 0.4% of their body weight, and were submitted to a regular work routine, one month before the ride. Two hours before the ride, horses were given half the amount of concentrate and the remainder at the middle of the ride.

The ride took place on 02/12/96, when the maximum temperature was 33.1ºC and relative humidity of 84% (Nhumirim farm metereological station data). The horses were ridden in pairs, in a trot averaging 8km per hour. All horses were allowed to drink water at midride. Horses did not receive electrolyte supplements before or during the ride.

Blood samples were collected before the ride (preride), at the mid-point of the ride (38km- midride), at the end of the ride (postride) and after a 30-minute recovery period (rest). Blood samples were stored in refrigerator and centrifuged within 30 minutes after collection. Sera were frozen until analyses were performed. Sweat was collected with help of pads covered with plastic, which were put under the saddle.

Serum concentrations of sodium (Na) and potassium (K) (mmol/l) were measured by atomic absorption (Harris & Popat, 1954) and phosphorus (P) (mmol/l) by colorimetry (Fick et al., 1976); chloride (Cl) concentration (mmol/l) was measured with commercial kits (Doles Reagentes); albumin (g/l) was measured with bromocresol green according to Doumas et al. (1971) and total protein (TP) (g/l) was measured with commercial kits (Labtest). Sweat concentrations of Na and K were determined using the same methods applied to serum.

Body weight and body condition were defined by visual scoring from 1 to 5, according to Carrol & Huntington (1988) and were recorded immediately before and after the ride. Heart rate (HR) was recorded from each horse at the time of blood collection using a stethoscope.

The group results were analysed separately by paired student's t test, comparing preride values to midride, postride and rest values. Despite of the presence of two factors (feeding and working) in animals of group 2, an analysis of variance was performed.

RESULTS

The changes in total serum protein, albumin and electrolyte concentrations during long distance exercise are shown in Table 1. There were significant increases in albumin at the mid-point of the ride in group 1 only. Sodium and phosphorus increased, while potassium and calcium decreased at midride, postride and 30 minutes after riding in both groups. Chloride and total protein did not change with the exercise. Concentrations of sweat electrolytes are presented in Table 2 for the two groups of Pantaneiro horses during ride endurance.

Alterations in body weight, score condition and heart rate are presented in Table 3. Horses lost about seven percent of body weight (26kg). One horse lost 33kg, 9.3 % of its body weight. Mean heart rate preride was similar in both groups (mean of 46.5 beats per minute) and increased during riding.

DISCUSSION

Exercise did not affect mineral requirements greatly, despite a possible increase in the requirements for minerals associated with the need of more energy to the muscles (Ca, Mg and P) and production of saliva and sweat (Cl-, Na+) (Pearson & Dijkman, 1994).

In addition to significant sweat loss, substantial losses of electrolytes occur. Electrolytes are essential for controlling membrane potential, muscle contraction, nerve condition, and enzyme reactions, and they play a central role in the physiological process of exercise. The thermoregulatory system of the horse is capable of maintaining homeothermy during prolonged exercise when they loose substantial sweat in order to maintain heat loss. Heat is transferred from the body surfaces to the environment by conduction, radiation, and evaporation, with sweat evaporation being the main way of loosing heat (McConaghy, 1994).

In this report, all horses were tired after the ride. However, they did not present medical problems. Measurements of total protein and albumin can provide an index of hydration (Rose & Hodgson, 1994). Some studies involving long distance exercise have shown increases in plasma protein and/or albumin, indicating a degree of dehydration (Carlson & Mansmann, 1974; Luck & Hall, 1980; Rose et al., 1980a; Rose et al., 1980b; Snow et al., 1982). In this study, total protein showed a small rise only, while albumin values increased only at midride in group 1. These results are in agreement with the observations of Carlson & Mansmann (1974) and Silva (1992), indicating that the horses had replaced their water losses over the course of the ride.

Sodium and chloride are directly affected by hydration status (Evans et al., 1995). Sodium concentration is maintained within narrow limits in the serum, ranging from 133 to 144mEq/l (Rose & Hodgson, 1994). In this report, sodium concentrations preride (Table 2) were below normal level, with a significant overall increase in sodium during the exercise in both groups, but group 2 had higher levels at rest. Sodium provides the greatest part of the osmotically active solute in the plasma and can influence the concentration of water in both intracellular and extracellular fluid compartments (Kirk & Bistner, 1985; Rose, 1986). The normal chloride level in the horses ranges from 94 to 104mEq/l (Rose & Hodgson, 1994). In this study, the preride values were below normal level and decreased in both groups during the exercise, although not significantly.

Natural diet of adult horse contains large quantities of potassium (Johnson et al., 1991). Potassium is the major intracellular cation and it is important for osmosis and normal balance of water and cellular biochemical functions. The normal serum potassium level in the horses ranges from 3.2 to 4.2 mEq/l (Rose & Hodgson 1994). High values observed at the preride stage are similar to those found by Snow et al. (1982). They observed marked increases in plasma K between the box and the start of the ride, which were considered to be caused by the release of K from muscle fibres during the beginning of the activity. Group 1 showed higher values, probably due to stress during exercise. Data showed a decrease in serum K during the ride, remaining in the normal range. According to Harris & Snow (1988) the extent of the increase in plasma K is dependent on the exercise intensity and the individual animal. For Beaumont et al. (1973), the plasma K concentration changes rapidly during maximal exercise but remains relatively stable in the first few minutes of recovery.

There are few studies of sweat electrolyte concentrations in endurance rides (Rose et al., 1980a; Snow et al., 1982). For these authors, the chloride loss in sweat was greater than the sodium loss. Comparing the data of this study with the data of Snow et al. (1982) it is observed that the mean sweat potassium concentrations were higher whereas sodium concentrations were lower. It should be considered that the Pantaneiro horses did not receive mineral suplementation before the ride.

Serum calcium decreased during exercise, whereas the serum phosphorus increased. These results are similar to those of Rose et al. (1983). Authors explained that the increase in phosphate concentrations may be related to phosphate liberation following ATP hydrolysis. The decrease in calcium can be explained by the fact that, during muscle contraction, calcium is required to bond with the troponin molecule to allow binding of actin and myosin, thus calcium ions move intracellularly to enable efficient muscular function. This difference is probably due to a greater loss of calcium by sweating. Large fluid and electrolyte losses cause a variety of clinical signs, referred to as exhaustive disease complex. This causes some respiratory problems, including synchronous diaphragmatic flutter (SDF). This condition is most commonly seen in endurance horses performing in hot and humid weather (McConaghy, 1994). The exact aetiology of SDF is unknown, but there appears to be some relationship to calcium, because it has been considered to be a result of calcium loss in sweat. According to Luck & Hall (1980) horses affected with SDF do respond to intravenous calcium therapy. Schryver et al. (1978) estimated calcium losses in sweat and suggested that, if not sustained, additional calcium may be required.

Thus, differences in results among reports can probably be attributed to the differences in climatic conditions and to the irregular use of electrolyte supplementation during rides as well as feeding, training, exercise type and body condition (Snow et al., 1982; Kerr & Snow, 1982).

Sweating rates can be estimated by weighing horses before and after the exercise (McConaghy, 1994). In this study, all horses lost weight, thus score conditions fell too. According to Pearson & Dijkman (1994) this loss can be tolerated if work seasons are short. Hinton (1977) found that horses should not enter long distance rides unless they are fit, because they loose less sweat.

Heart rate is a reliable clinical index of fatigue in an endurance ride (Rose, 1986). Heart rate measurements during exercise have been used to describe the intensity of work, to measure fitness, and to study the effects of training and detraining (Evans, 1994). A direct relationship occur between heart rate and amount of energy used during any given time. The 'true resting heart rate', when the animal is resting quietly in a pasture will fall between 24 and 36 beats/min (Ridgway, 1994). In relaxed horses, resting heart rate is usually in the range 25 to 40 beats/min (Evans, 1994) and when saddled and ready to work it falls between 36 and 48 beats/min, similar to mean values found in this study (46 and 47 beats/min, for group 2 and 1, respectively). Recovery heart rates can be used for determining the level of fitness and the ability to continue during exercise. Horses should be rested until the HR drops to 64 beats/min or less, no more than 15 min after ceasing the exercise (Ridgway, 1994). In this study, horses in group 1 and group 2 showed mean values of 60 and 56 beats/min after 30 minutes of rest, respectively, indicating a good recovery response. Group 2 showed better adaptation to the level of exercise (applied stress) because they had been working. Rose & Hodgson (1982) disqualified horses with HR that failed to return below the prescribed limit of 60 beats/min 30 minutes after the ride, whereas Rose (1984) cited by Rose (1986) eliminated horses with heart rates greater 55 beats/min 30 minutes after arriving at the mid-point of a ride. Asheim et al. (1970) suggested that the use of submaximal work tests without taking the maximal HR into consideration may introduce an error. Thus, it can be used only if the HR is as high as possible in order to reduce the error.

CONCLUSIONS

Although serum total protein concentrations did not increase and chloride values did not decrease significantly, there was a slight degree of haemoconcentration and/or dehydration in the Pantaneiro horse during a 76km endurance ride. Pantaneiro horses showed serum sodium and chloride concentrations preride below normal values. Electrolytes supplements are recommended for Pantaneiro horses in exercise.

ACKNOWLEDGEMENTS

This research was partially supported by the Ministry of Agriculture, to which authors are grateful. They also thank Dr. Arthur Mariante for encouraging the project; people that work the cattle and horses at Nhumirim farm; Ernande Ravaglia and Paule Jeanne Vieira Mendes for assistance in collecting data in the field; Ernande Ravaglia, Maria Davina R. dos Santos, Valdete dos Santos Sanchez and Eliney Gaertner for the laboratory analyses of the samples; Laura Seidl, Regina Baruki Fonseca e Vânia da Silva Nunes for helping us with the English version.

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Datas de Publicação

  • Publicação nesta coleção
    07 Jun 2002
  • Data do Fascículo
    Jun 2001

Histórico

  • Recebido
    23 Jan 2001
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