关键词: 热应激, 耐热性, 湖羊, 生理指标, 血清生化指标, 免疫功能

Abstract: The purpose of this experiment was to explore the changes in physiological indices， serum biochemical indices and immune function of Hu sheep with different heat tolerance，and to provide reference for analyzing the heat tolerance mechanism of Hu sheep and formulating strategies to alleviate heat stress of sheep. From July 1 to August 20，under the condition of an average THI（Temperature⁃Humidity Index）of 85.5，a total of 811 multiparous，non⁃pregnant ewes with consistent parity（all having given birth twice），good health status，and identical feeding management were selected and raised collectively in a single shed. Indicators such as respiratory rate，rectal temperature，and heart rate were measured. Using principal component analysis and membership function analysis，heat⁃resistant（HR）Hu sheep（n=30）and heat⁃sensitive（HS）Hu sheep （n=30）were identified. The results showed that the respiratory frequency，rectal temperature and heart rate of Hu sheep in HS group were significantly higher than those in HR group（P<0.01）. WBC and HGB in the blood routine of Hu sheep in HR group were significantly higher than those in HS group（P<0.01），and LYM was significantly higher than that in HS group（P<0.05）. The contents of serum HSP70 and HSP90 in HR group were significantly higher than those in HS group（P<0.01）. The contents of T3， T4 and COR in HR group were significantly higher than those in HS group（P<0.01）. The concentrations of TNF⁃α，IL⁃1β and IL⁃6 in HR group were also significantly higher than those in HS group（P<0.01）. In conclusion，compared with HS Hu sheep，HR Hu sheep exhibit stronger heat stress resistance and immune capacity.

Key words: Heat stress, Heat resistance, Hu sheep, Physiological indicators, Serum biochemical indexes, Immune function