Hodgson D R, Davis R E, McConaghy F F
Department of Animal Health University of Sydney, Camden, NSW, Australia.
Br Vet J. 1994 May-Jun;150(3):219-35. doi: 10.1016/S0007-1935(05)80003-X.
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 l h-1 reported. The 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 increasing the risk of heat induced illness. A basic understanding of the thermoregulatory responses in the exercising horse is imperative if heat induced illnesses are to be avoided. If they do occur rapid recognition and effective management are essential.
运动过程中，储存的能量转化为机械能的效率相对较低，大约80%的能量以热量的形式散发出去。相对于许多物种而言，马明显处于劣势，因为它具有较高的代谢能力，但散热的表面积较小，尤其是出汗蒸发是主要的散热方式。在大多数运动条件下，至少三分之二的代谢热负荷通过这种方式散发，据报道出汗量超过10升/小时。其余由运动引起的热负荷必须储存起来（表现为核心体温升高），通过呼吸道散发，或通过其他机制散失。运动过程中，呼吸散热可占代谢热负荷的25%以上。在环境温度和湿度较高的情况下，蒸发散热将受到限制，如果继续运动，热应激风险将增加。此外，同时发生的脱水会降低从核心到外周的热传导，进一步增加热致疾病的风险。如果要避免热致疾病，必须对运动中的马的体温调节反应有基本的了解。如果确实发生了热致疾病，快速识别和有效管理至关重要。
