22 Comparison of post-exercise cooling methods in horses

Abstract

Exertional heat illness (EHI) following strenuous exercise under hot and humid conditions can be detrimental in horses. Direct cooling after intense exercise is necessary to prevent EHI. Therefore, this study aimed to evaluate the efficacy of 3 cooling methods in horses post treadmill exercise. Five mature geldings were treadmill exercised on 3 consecutive weeks to determine the effect of 3 post-exercise cool-down methods (5 × 3 Latin square design). These methods were (i) no water application (W no ), (ii) cold water application only (W only ; pouring 30 L of cold water (6°C) every min for 6 min) and (iii) cold water application with scraping (W scraping ; cold water (6°C) application followed by scraping after each water application). After 6 min active cool-down phase, the horses were walked in-hand (walking phase) for 4 min and stood (standing phase) for 35 min. Central venous temperature (T CV ) and rectal temperature (T R ) were selected and measured simultaneously. The collected temperatures were paired and statistically analyzed by Wilcoxon signed rank test to assess the efficiency of cooling between methods. The room temperature and humidity in the treadmill room for the treadmill exercise was (mean ± SD) 27.2 ± 1.3°C and 49.9 ± 7.2% and in the corridor for cooling down was 30.0 ± 2.2°C and 49.0 ± 8.6%. Greater T CV and T R reductions were observed when cold water (W only & W scraping ) was applied compared with no water application (W no ) (T CV : −0.91°C for W only -W no , P < 0.001, −0.84°C for W scraping -W no , P < 0.001; T R : −0.31°C for W only -W no , P < 0.001, −0.29°C for W scraping -W no , P < 0.001), and overall the water application had more cooling down effect on T CV than T R (−0.57°C, P < 0.001). Between the 2 applied cold water methods, significantly lower body temperatures (T CV −0.11°C, P = 0.01; T R −0.03°C, P = 0.01) were observed with W only than W scraping . This study demonstrates that constant contact with water is more important for heat conduction and more effective than producing and using sweat evaporation to remove heat. Application of water without scraping may help decrease the core body temperature in horses more effectively in the early stage of EHI.