热应激状态下羊的体温调节

Heat Stress and Thermoregulation of Sheep and Goats

热应激是由高温环境所引起的,在炎热的气候条件下,当环境有效温度超过羊的等热区上限温度时,羊就会出现热应激。由热应激引发的不良影响广泛存在,不仅严重影响羊的生存质量,而且导致羊体温升高、生长性能降低、免疫力减弱以及肉品质下降。本文综述了导致羊产生热应激的因素以及热应激条件下的体温调节机制。在热应激的情况下,机体通过吸收环境辐射热和累积机体代谢产热,使机体获得很高的热负荷,超过了机体的散热能力。暴露在高温环境中的羊只,可通过增加机体散热消除过多的热负荷。当空气温湿度发生变化时,作为恒温动物,绵羊和山羊可以通过调整自身的产热量、采食量、饮水量、呼吸频率和行为等方式,来维持机体产热和散热的平衡。总之,羊可以利用复杂有效的散热机制维持体温平衡,适应高温环境。

The heat stress is mainly induced by high ambient temperature. The sheep/goats suffer from heat stress when the effective ambient temperature is higher than thermoneutral zone in hot climates. However, the adverse effects caused by heat stress are widely existed, which are not only seriously affecting the quality of animals＇ life, but also increasing body temperature, decreasing growth performance, weakening immunity and decreasing meat quality of sheep or goat. The objective of this paper is to review the reason of heat stress and thermoregulation in sheep/goats. The sheep/goats obtain high heat load through the solar radiation heat and metabolic heat increment. The exposure of sheep/goats to elevated ambient temperatures induces an increase in the dissipation of excess body heat, in order to negate the excessive heat load. As one kind of homeothermic animals, when the ambient temperature and humidity changed, sheep and goats can adjust responses of thermoregulation such as heat production, feed intake, water intake, respiratory rate and behavior to maintain thermal balance. In summary, sheep/goats can use complex and effective heat dissipation mechanisms to maintain balance of body temperature, and to adapt to hot climate conditions.