Heat storage in horses during submaximal exercise before and after humid heat acclimation (original) (raw)
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Equine sweating responses to submaximal exercise during 21 days of heat acclimation
Journal of applied physiology (Bethesda, Md. : 1985), 1999
This study examined sweating responses in six exercise-trained horses during 21 consecutive days (4 h/day) of exposure to, and daily exercise in, hot humid conditions (32-34 degrees C, 80-85% relative humidity). On days 0, 3, 7, 14, and 21, horses completed a standardized exercise test on a treadmill (6 degrees incline) at a speed eliciting 50% of maximal O(2) uptake until a pulmonary artery temperature of 41.5 degrees C was attained. Sweat was collected at rest, every 5 min during exercise, and during 1 h of standing recovery for measurement of ion composition (Na(+), K(+), and Cl(-)) and sweating rate (SR). There was no change in the mean time to reach a pulmonary artery temperature of 41.5 degrees C (range 19.09 +/- 1.41 min on day 0 to 20.92 +/- 1.98 min on day 3). Peak SR during exercise (ml. m(-2). min(-1)) increased on day 7 (57.5 +/- 5. 0) but was not different on day 21 (48.0 +/- 4.7) compared with day 0 (52.0 +/- 3.4). Heat acclimation resulted in a 17% decline in SR durin...
Effects of Pre-Cooling on Thermophysiological Responses in Elite Eventing Horses
Animals
In this study, we examined the effects of pre-cooling on thermophysiological responses in horses exercising in moderate environmental conditions (average wet bulb globe temperature: 18.5 ± 3.8 °C). Ten international eventing horses performed moderate intensity canter training on two separate days, and were either pre-cooled with cold-water rinsing (5–9 °C for 8 ± 3 min; cooling) or were not pre-cooled (control). We determined velocity (V), heart rate (HR), rectal temperature (Tre,), shoulder and rump skin temperature (Tshoulder and Trump), plasma lactate concentration (LA), gross sweat loss (GSL), and local sweat rate (LSR), as well as sweat sodium, chloride and potassium concentrations. The effect of pre-cooling on Tre was dependent on time; after 20 min of exercise the effect was the largest (estimate: 0.990, 95% likelihood confidence intervals (95% CI): 0.987, 0.993) compared to the control condition, resulting in a lower median Tre of 0.3 °C. Skin temperature was also affected b...
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 ...
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.
Journal of Equine Veterinary Science, 2001
An experiment was conducted utilizing twenty mature Quarter Horses to establish physiologic responses to reining training under conditions conducive to heat stress. Ten of the horses were acclimatized to ambient conditions [30°C, 80% relative humidity (RH)] for 28 days while the other ten were acclimatized simultaneously to 20°C and 50% RH in an air-conditioned facility. On day 28 standard exercise testing (SET) 1 was conducted in ambient conditions (30°C, 80% RH) for both groups of horses and was repeated on day 30 and day 32 of the protocol. Heart rate and plasma lactate concentration revealed that galloping circles, spinning and stopping were more taxing maneuvers for the unacclimatized horses on day 28. However, these differences were less significant on day 30 and were not observed on day 32 indicating that it took the horses approximately five days to become acclimatized to ambient conditions. Respiration rate and rectal temperature were higher in the cool-treated horses during rest and the recovery period on day 28. These differences were only seen in the early stages of recovery on day 30 and totally disappeared on day 32. Packed cell volume was lowest in the cool-treated horses on day 28 during the SET and most of the recovery period, which is likely reflective of the absence of a substantial amount of sweating on the first day of acclimatization. This difference was still present, however, less apparent on day 30 and completely absent on day 32. Plasma cortisol concentrations were significantly higher during recovery in the cool-treated horses on day 28 and day 30, but they were not different on day 32.
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.
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...
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.