Department of Veterinary Sciences, Polo Universitario Dell'Annunziata, University of Messina, 98168, Messina, Italy.
Department of Engineering, University of Messina, C/da Di Dio (S. Agata), 98166, Messina, Italy.
Int J Biometeorol. 2022 Aug;66(8):1601-1611. doi: 10.1007/s00484-022-02304-3. Epub 2022 May 20.
Thermoregulation is an important mechanism to ensure thermal homeostasis. In horses, different housing conditions could influence this mechanism by exposing animals to different microclimates. The circadian rhythm of body temperature is well known. For this reason, we wanted to investigate the daily rhythm of cutaneous (jugular, shoulder, inner thigh and croup) temperature in comparison to rectal temperature in athletic horses kept under two different housing conditions. Ten clinically healthy Italian Saddle horses were divided into two equal groups: the first group was housed in individual boxes, and the second group was kept in paddocks. In all horses, rectal and cutaneous temperature measurements were performed every 4 h for 48 consecutive hours during different seasons (spring, summer, autumn and winter), respectively, by means of digital and infrared thermometers. Ambient temperature, relative humidity and ventilation were recorded simultaneously. A general linear model (GLM) was applied to the recorded temperature values displaying a significant effect of season, time of day, site of recording and housing condition (p < 0.001). No statistical differences were found between the two days of monitoring (p = 0.49). A trigonometric statistical model (single cosinor method) was applied to investigate the circadian rhythm of rectal and cutaneous temperatures in the two different groups. Our results showed circadian rhythmicity of rectal temperature during all seasons and in both groups. Cutaneous temperature shows daily rhythmicity that was different in the various regions and was influenced by housing conditions and seasons. Application of GLM also showed a statistically significant effect of season and site of recording (p < 0.0001) on all circadian parameters and of management condition on amplitude and robustness (p < 0.0001). No statistical differences between the two days of monitoring were observed (p = 0.68). These findings are probably due to the animals' thermoregulatory mechanisms ensuring heat exchange between the body and the environment, and that was influenced by the microclimate. In particular, the microclimate influenced the thermodispersion disrupting the daily rhythmicity of some body regions, in horses kept in boxes. Only the temperate climatic conditions observed in summer guarantee the expression of the daily rhythmicity of all body surfaces in both management conditions. These results contribute to the knowledge of the mechanisms of homeostasis and control of body temperature in the athletic horse kept in different housing conditions, with a chronophysiological interpretation that completes the proper management of thermal well-being in horses.
体温调节是确保热平衡的重要机制。在马中，不同的饲养条件可能通过使动物暴露于不同的小气候中来影响该机制。体温的昼夜节律是众所周知的。因此，我们想研究在两种不同饲养条件下，运动马的皮肤（颈静脉、肩部、大腿内侧和臀部）温度与直肠温度的日常节律。将 10 匹临床健康的意大利鞍马分为两组：第一组被安置在单独的箱子中，第二组被安置在围场中。在所有马中，通过数字温度计和红外线温度计，在不同季节（春季、夏季、秋季和冬季）分别连续 48 小时每 4 小时进行直肠和皮肤温度测量。同时记录环境温度、相对湿度和通风情况。应用一般线性模型（GLM）对记录的温度值进行分析，显示季节、一天中的时间、记录部位和饲养条件有显著影响（p<0.001）。在两天的监测中没有发现统计学差异（p=0.49）。应用三角统计模型（单余弦法）研究两组中直肠和皮肤温度的昼夜节律。我们的结果表明，在所有季节和两组中，直肠温度都具有昼夜节律性。皮肤温度显示出不同的日常节律性，并且受到饲养条件和季节的影响。GLM 的应用还显示出季节和记录部位（p<0.0001）对所有昼夜节律参数以及管理条件对振幅和稳健性（p<0.0001）有统计学显著影响。在两天的监测中没有观察到统计学差异（p=0.68）。这些发现可能是由于动物的体温调节机制确保了身体与环境之间的热交换，并且该机制受到微气候的影响。特别是，在盒子中饲养的马，微气候会影响热分散，破坏一些身体部位的日常节律性。只有在夏季观察到的温和气候条件才能保证在两种管理条件下所有身体表面的日常节律性表达。这些结果有助于了解在不同饲养条件下运动马的内稳态和体温控制机制，并从生理时间的角度对其进行解释，从而完善马的热舒适管理。
