Equine sweating responses to submaximal exercise during 21 days of heat acclimation (original) (raw)
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Heat storage in horses during submaximal exercise before and after humid heat acclimation
Journal of applied physiology (Bethesda, Md. : 1985), 2000
The effect of humid heat acclimation on thermoregulatory responses to humid and dry exercise-heat stress was studied in six exercise-trained Thoroughbred horses. Horses were heat acclimated by performing moderate-intensity exercise for 21 days in heat and humidity (HH) [34.2-35.7 degrees C; 84-86% relative humidity (RH); wet bulb globe temperature (WBGT) index approximately 32 degrees C]. Horses completed exercise tests at 50% of peak O(2) uptake until a pulmonary arterial temperature (T(pa)) of 41.5 degrees C was attained in cool dry (CD) (20-21.5 degrees C; 45-50% RH; WBGT approximately 16 degrees C), hot dry (HD 0) [32-34 degrees C room temperature (RT); 45-55% RH; WBGT approximately 25 degrees C], and HH conditions (HH 0), and during the second hour of HH on days 3, 7, 14, and 21, and in HD on the 18th day (HD 18) of heat acclimation. The ratios of required evaporative capacity to maximal evaporative capacity of the environment (E(req)/E(max)) for CD, HD, and HH were approximate...
Journal of applied physiology (Bethesda, Md. : 1985), 2000
This study determined the plasma volume (PV) and ion responses to heat acclimation and exercise in six trained Thoroughbred horses during 21 days of exposure to heat and humidity (33 degrees C, 83% relative humidity) for 4 h/day. During the 2nd h on days 0, 3, 7, 14, and 21, horses performed a standardized treadmill test, running at 50% of peak O(2) uptake until pulmonary artery temperature reached 41.5 degrees C. Heat acclimation resulted in an increase in PV from 21.3 +/- 1.1 liters on day 0 to 24.3 +/- 1.0 liters on day 14, returning to 22.6 +/- 0.9 liters on day 21. The corresponding total plasma protein contents were 1,273 +/- 53, 1,455 +/- 81, and 1,377 +/- 57 g, respectively, and increases in total plasma Na(+) plus Cl(-) content were 5,145 +/- 126, 5,749 +/- 146, and 5,394 +/- 114 mmol, respectively. Thus changes in PV were accompanied by direct changes in plasma protein and osmolyte contents. With exercise on day 0, PV decreased by 7.1 +/- 0.7% at 5 min of exercise and rema...
Plasma and sweat electrolyte concentrations in the horse during long distance exercise
Equine Veterinary Journal, 1980
SummaryBlood samples were taken from 20 horses competing in a 100 km endurance ride and plasma concentrations of sodium, potassium, chloride, bicarbonate and protein measured. Measurements were performed on samples taken before the ride (pre‐ride), at the mid point and end of the ride and after a 30 min recovery period (post‐ride). Sweat samples were collected from 6 horses competing in the endurance ride and 14 horses competing in a 3‐day event competition and sweat concentrations of sodium, potassium and chloride measured. There were substantial decreases in plasma electrolyte concentrations, which were greater than previously reported. Decreases from pre to post ride samples of 5 mmol/1 of sodium, 1.2 mmol/1 of potassium and 16 mmol/1 of chloride were found. These losses appeared to be related directly to sweat electrolyte concentrations, where potassium and chloride had relatively greater concentrations than in plasma.RésuméDes échantillons de sang ont été prélevés sur 20 chevau...
Exercise-induced changes in skin temperature and blood parameters in horses
Archiv für Tierzucht, 2019
The aim of the study was to assess the effects of training on haematological and biochemical blood parameters as well as on the changes in body surface temperature in horses. In order to identify the predictive value of surface temperature measurements as a marker of animal's performance, their correlations with blood parameters were investigated. The study was carried out on nine horses divided into two groups: routinely ridden and never ridden. Infrared thermography was used to assess surface temperature changes before (BT) and just after training (JAT) on a treadmill. Seven regions of interest (ROIs) located on the neck, shoulder, elbow, back, chest, gluteus and quarter were analysed. The blood samples were taken BT, JAT and 30 min after training (30AT). Haematological parameters including white blood cells, lymphocytes (LYMs), monocytes (MONOs), granulocytes (GRAs), eosinophils (EOSs), haematocrit (HCT) and platelets (PLTs) as well as biochemical parameters such as glucose (GLUC), urea, Na + , K + and Ca 2+ , and creatine phosphokinase (CPK) were analysed. Our results indicated a significant increase in surface temperature JAT (p = 0.043) in the neck, shoulder, elbow, gluteus and quarter in routinely ridden horses. Significant changes in EOS (p = 0.046) and HCT (p = 0.043) in the case of the never-ridden and routinely ridden group, respectively, were found between the times of blood collection. In addition, there was a significant effect of the horse group and the time of blood collection on the CPK activity (p = 0.025 to p = 0.045) and urea concentrations (p = 0.027 to p = 0.045). In the routinely ridden horses, there were significant correlations between the changes in MONO (ρ = 0.40), GRA (ρ = −0.40), PLT (ρ = −0.77), HCT (ρ = −0.36), GLUC (ρ = 0.56) and urea (ρ = 0.56) and the total ROI temperature changes. Moreover, significant correlations between the changes in MONO (ρ = −0.86), EOS (ρ = −0.65), GLUC (ρ = 0.85), urea (ρ = 0.85), Na + (ρ = 0.59) and K + (ρ = −0.85) and the total ROI temperature changes were found in never-ridden horses. Different changes in body surface temperature and blood parameters in routinely ridden and never-ridden horses could be associated with different conditioning and performance. A significantly higher surface temperature in routinely ridden horses, as well as the dynamics of changes in HCT, CPK and urea after training indicate better performance of these horses. Significant correlations between MONO, GLUC, and urea and a total ROI surface temperature as well as a negative correlation between MONO and the total ROI temperature in never-ridden horses indicated poor performance.
Frontiers in Physiology, 2021
Establishing proper policies regarding the recognition and prevention of equine heat stress becomes increasingly important, especially in the face of global warming. To assist this, a detailed view of the variability of equine thermoregulation during field exercise and recovery is essential. 13 endurance horses and 12 trotter horses were equipped with continuous monitoring devices [gastrointestinal (GI) pill, heartrate (HR) monitor, and global positioning system] and monitored under cool weather conditions during four endurance rides over a total of 80 km (40 km loops) and intense trotter track-based exercise over 1,540 m. Recordings included GI temperature (Tc), speed, HR and pre- and post-exercise blood values. A temperature time profile curve of Tc was constructed, and a net area under the curve was calculated using the trapezoidal method. Metabolic heat production and oxygen cost of transport were also calculated in endurance horses. Maximum Tc was compared using an independent ...
The Veterinary Journal, 2002
To determine the effects of exercise, high heat and humidity and acclimation on plasma adrenaline, noradrenaline, b-endorphin and cortisol concentrations, five horses performed a competition exercise test (CET; designed to simulatethespeedandendurancetestofathree-dayevent)incooldry(CD)(20 C/40%RH)andhothumid(30 C/ 80% RH) conditions before (pre-acclimation) and after (post-acclimation) a 15 day period of humid heat acclimation. Plasma adrenaline and noradrenaline concentrations pre-acclimation were significantly increased compared with exercisein the CD trial at the end of PhasesC (P`0.05) and D (P`0.05and P`0.01, respectively) and at 2 min recovery (P`0.01), with adrenaline concentrations still elevated after 5 min of recovery (P`0.001). Plasma b-endorphin concentrations were increased at the end of Phases C (P`0.05) and X (P`0.01) and at 5 and 30 min recovery (P`0.05) in the pre-acclimation session. Plasma cortisol concentrations were elevated after the initial warmupperiodpre-acclimation(P`0.01)andattheendofPhaseC(P`0.05),comparedwiththeCDtrial.A15day period of acclimation significantly increased plasma adrenaline concentrations at 2 min recovery (P`0.001) and plasma cortisol concentration at the end of Phase B (P`0.01) compared with pre-acclimation. Acclimation did not significantly influence noradrenaline or b-endorphin responses to exercise, although there was a trend for plasma b-endorphin to be lower at the end of Phases C and X and after 30 min recovery compared with pre-acclimation. Plasma adrenaline, noradrenaline, b-endorphin and cortisol concentrations were increased by exercise in cool dry conditions and were further increased by the same exercise in hot humid conditions. Exercise responsespost-acclimation suggest that adrenaline andnoradrenaline may play a role intheadaptation of horses to thermal stress and that changes in plasma b-endorphin concentrations could be used as a sensitive indicator of thermal tolerance before and after acclimation. The use of plasma cortisol as a specific indicator of heat stress and thermal tolerance before or after acclimation in exercising horses appears limited.
Equine sweat composition: effects of adrenaline infusion, exercise and training
Equine Veterinary Journal, 2010
Significant alterations in plasma electrolyte concentrations have been reported in horses following prolonged exercise, resulting from loss of hypertonic sweat. Sweat was collected from 10 horses undergoing a 10 week training programme; 5 at moderate intensity, to speeds of 10 m/s and 5 at low intensity, to speeds of 5 m/s. Sweat was collected from 2 sites in response to a submaximal exercise test (30 min at 50% VO2max and during an adrenaline infusion (dose mean +/- s.d.; 0.3 +/- 0.05 g/kg over 30 min). Sweat samples were analysed for sodium, chloride, potassium, protein, magnesium, calcium and urea concentrations. Sweat produced in response to exercise and adrenaline infusion was hypertonic and showed no significant differences in composition following training. However, the [NaCl] of sweat rose with increased duration of sweating. Sweat produced in response to adrenaline infusion was more dilute than that produced in response to exercise, which may be related to sympathetic outflow during exercise.
Thermoregulation in the horse in response to exercise
British Veterinary Journal, 1994
Conversion of stored energy into mechanical energy during exercise is relatively inefficient with approximately 80% of the energy being given off as heat. Relative to many species the horse suffers an apparent disadvantage by possessing a high metabolic capacity yet a small surface area for dissipation of heat, particularly as evaporation of sweat is the major method of heat dissipation. Under most conditions of exercise at least two-thirds of the metabolic heat load is dissipated via this means with sweat losses of more than 10 1 h reported. T he remaining exercise induced heat load must be stored (reflected by an increase in core temperature), dissipated across the respiratory tract or lost via other mechanisms. Respiratory heat loss can account for dissipation of more than 25% of the metabolic heat load during exercise. Under conditions where ambient temperature and humidity are high, evaporative heat loss will be limited thereby posing an increased risk of thermal stress if exercise is continued. Additionally, concurrent dehydration reduces conductance of heat from core to periphery, further âˆ'1 Purchase Export Previous Previous article Next Next article Check if you have access through your login credentials or your institution.