Effect of heat stress on some physiological characteristics of Awassi Sheep in Iraq

Abstract

Thirty four growing male Awassi I sheep were used in an attempt to assess a useful heat tolerance index by using some physiological and biochemical changes due to solar radiation exposure. The changes in body temperature, hemoglobin, haematocrit, total body water, triiodothyronine and cortisol was found to be not correlated with body gain decrease due to heat stress. Therefore, it can not be used to predict heat adaptability in this study.During the hot-humid summer (temperature humidity index =76-89°) daily body and solids gain,, dry matter intake, thyroid, liver and kidney functions were reduced. However, total body water, water intake, rectal temperature and respiratory rate were increased. Treatment of heat stressed sheep by chilled drinking water significantly improved daily body and solids gain and reduced the effects of heat stress on thermal and water balances and thyroid, liver and kidney functions. Tap water sprinkling failed to alleviate the adverse effects of heat stress.