Measuring heat stress indices in naturally ventilated sheep shade barns in the localenvironment of Al-Ahsa of Saudi Arabia

摘要

In the harsh desert environment, a high degree of thermal stress affects sheep farming. The aim of this study was to assess thermal heat stress levelsaffecting sheep welfare in a naturally ventilated shade barn under the climatic conditions of Al-Ahsa, Saudi Arabia. Environmental parameters withinand outside the sheep barn were observed, and two linear models were developed to calculate the temperature humidity index (THI) under shade ofthe sheep barn. Furthermore, an adjusted temperature humidity index (THIadj) was calculated that considered solar radiation and air velocity. Theresults showed that air temperature and relative humidity levels under shade were strongly dependent on the outdoor climate. The mean value ofTHIshade was significantly (p < 0.05) lower (-3.5%) than that of THIout. During summer, sheep experienced the dominant heat category, extreme severeheat stress (category IV), for 99.7% of the total hours., whereas, during spring, the expectation was that sheep would experience heat stress (categoryIV) no less than 45.8% of times. In autumn, potential heat stress values were in categories I, II, III and IV for 20.5%, 5.8%, 14.5% and 59.2% of thetotal hours, respectively, which indicated a high probability of heat stress occurrence. In winter, heat stress was generally absent (category I). Theadjusted thermal heat index was particularly important for outdoor animals. The mean value of THIadj was significantly (p < 0.05) greater (+10%) thanthat of THIout when solar radiation was considered. Therefore, sheep farmed in the climate of Al-Ahsa, Saudi Arabia will be under extreme, severe heatstress (category IV) from April to October, with several potential effects on animal welfare and productivity, therefore, shading is an advisableprotection procedure.