Short-term thermoregulatory responses of horses to brief changes in ambient temperature

摘要: The first objective of this thesis is to study thermoregulation in standing horses, especially the short-term physiological responses brief changes thermal environment. My hypothesis that characteristics thermoregulatory system reflects evolutionary background horses. Horses evolved on steppe, where they lived herds and fled when danger. As homeothermic animals, have maintain an almost constant body core temperature by losing excess heat from a constantly ongoing internal production despite On temperature, radiation wind can vary greatly, which affects means loss. In case flight, horse has lose load induced muscular work so as restore temperature. A second measure properties losses horses improve management housing was performed climatic chamber five at six different levels: -3°C, 6°C, l5°C, 20°C, 30°C 37°C, results, discussed frame story, are presented four articles: I. Dissipation exposed ambient temperatures between - 3°C 37°C. II. Thermal insulance peripheral tissue coat III. Effects air or altered insulation IV. Climatic energy demand I found increase evaporative loss (50 450 W m^-2) sweating increasing respiratory rate warm hot environments. This mechanism, handle exercised-induced load. regulated both skin (0.015 0.100 m2 K W^-1) compromise provide but not be limiting processes sweating. coat, being thin insulating layer hair, probably best physical for allowing evaporation whilst providing protection heavy solar loads during day radiative night. However, cold environments may sufficient Since graze most day, compensate excessive regulating feed intake. climates, needs extra feed, called demand, estimated 2.78 m^-2 per degree Celcius below lower critical thermoneutral zone range 5°C 25°C. fact live herd advantage since it enables members protect help each other environments, e. g. close together limit area. conclusion my synthesis thermoreglatory advantageous animal been able flee danger freely steppe.