Real-time monitoring of the core body temperature in endurance horses during field exercise

Abstract

<jats:sec><jats:title>Introduction</jats:title><jats:p>Continuous monitoring of core body temperature may provide useful information about the thermal response to metabolic heat load and environmental challenges. The aim of this study was to evaluate a telemetric gastrointestinal (<jats:styled-content style="fixed-case">GI</jats:styled-content>) pill (Equivital®) measuring gastrointestinal temperature (<jats:styled-content style="fixed-case">GT</jats:styled-content>) during endurance exercise. It was hypothesised that a temperature and metabolic heat profile could be established.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>The <jats:styled-content style="fixed-case">GI</jats:styled-content> pill was administered to 6 horses by nasogastric tube (n = 3) or modified‐drench gun (n = 3), the day before competition. During competition, <jats:styled-content style="fixed-case">GT</jats:styled-content>, skin temperature and heart rate (<jats:styled-content style="fixed-case">HR</jats:styled-content>) were recorded (by Equivital® belt). Other data collected included body weight and rectal temperature (<jats:styled-content style="fixed-case">RT</jats:styled-content>), <jats:styled-content style="fixed-case">GPS</jats:styled-content>/<jats:styled-content style="fixed-case">HR</jats:styled-content> monitor information, and environmental conditions using a data logger. Metabolic heat production was calculated [1] and <jats:styled-content style="fixed-case">GT</jats:styled-content> correlations were explored using simple correlation estimates (P&lt;0.05).</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Data were collected from 6 horses during 80 km (n = 4 horses) and 100 km (n = 2) competition days with mean data loss of 7.4% (±2.4%). <jats:styled-content style="fixed-case">GT</jats:styled-content> profiles showed increasing temperature with cumulative metabolic heat production, and time to reach maximum <jats:styled-content style="fixed-case">GT</jats:styled-content> was 2.14–6.29 h (maximum <jats:styled-content style="fixed-case">GT</jats:styled-content> range: 38.4–39.5°<jats:styled-content style="fixed-case">C</jats:styled-content>). During exercise (7 h 6 min ± 1 h 3 min duration), mean and maximum speeds ranged from 10.1–14.5 km/h and 23.5–30.8 km/h, respectively. No correlation was found between <jats:styled-content style="fixed-case">GT</jats:styled-content> and <jats:styled-content style="fixed-case">HR</jats:styled-content>, skin, or environment temperature. Maximum <jats:styled-content style="fixed-case">GT</jats:styled-content> increased with bodyweight (r = 0.775, P = 0.08). <jats:styled-content style="fixed-case">GT</jats:styled-content> was systematically higher than <jats:styled-content style="fixed-case">RT</jats:styled-content> (mean difference +0.46°<jats:styled-content style="fixed-case">C</jats:styled-content>).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p><jats:styled-content style="fixed-case">GT</jats:styled-content> was recorded successfully during competition with minimal data loss. The <jats:styled-content style="fixed-case">GI</jats:styled-content> pill has great potential as a method to further investigate thermoregulation in horses under field conditions.</jats:p></jats:sec><jats:sec><jats:title>Ethical Animal Research</jats:title><jats:p>All studies were performed under the Adelaide <jats:styled-content style="fixed-case">A</jats:styled-content>nimal <jats:styled-content style="fixed-case">E</jats:styled-content>thics <jats:styled-content style="fixed-case">C</jats:styled-content>ommittee, <jats:styled-content style="fixed-case">U</jats:styled-content>niversity of Adelaide. <jats:styled-content style="fixed-case">E</jats:styled-content>xplicit owner informed consent for participation in this study is not stated. <jats:bold>Sources of funding:</jats:bold> The equipment for the project was funded by the Faculty of Science ‘Grant for minor equipment’, <jats:styled-content style="fixed-case">U</jats:styled-content>niversity of Adelaide, <jats:styled-content style="fixed-case">A</jats:styled-content>ustralia. <jats:bold>Competing interests:</jats:bold> none.</jats:p></jats:sec>