English Title: Physiological responses of Naimey sheep to heat stress challenge under semi-arid environments

The effect of heat stress on body temperature, heart rate, respiration rate and haematological and serum biochemical parameters was evaluated in 8 Naimey [Ne'imi] sheep (51.0±2.66 kg body weight). The sheep were divided into 2 groups which were placed in 2 rooms. One room (control) had an average temperature (23.6OC and 50% relative humidity), while in another room (experimental) the temperature was gradually increased from 23.6 to 33-38.5 OC. The study lasted for 5 weeks. It was shown that heat stress significantly reduced the daily average heart rate and increased rectal temperature, respiration rate, skin temperature and haematocrit. Serum triiodothyronine and thyroxine levels were also affected by heat stress, though not significantly. In conclusion, heat stress affects some physiological parameters of sheep