Effects of Nutritional and Thermal Stress and Chromium Supplementation on Physiological Responses of Desert Sheep

Abstract

The aim of this study was toevaluate the effects of nutritional stress, exposure tosolar radiation and chromium supplementation on thermoregulation and blood constituents in desert sheep. In experiment 1, the physiological responsesof ewes to food and water deprivation for three days and realimentation for three days were evaluated under summer conditions. Water and food deprivation and water deprivation resulted,respectively, in 15.92 % and 11.34 % loss in mean body weight (BW) compared with control. Upon rehydration, sheep were able to regain their BWlosses within two days. The food intake decreased progressively following water deprivation and returned to the control level within the days of rehydration. There was a gradual increase in rectal temperature (Tr) during dehydration which returned to the normal level after drinking. Food and water deprivation reduced respiratory rate (RR). The marked increase in packed cell volume (PCV), haemoglobin concentration (Hb) and total leukocytes count (TLC) associated with dehydration returned to the normal level after rehydration. Plasma glucose level increased progressively and significantly during water and food deprivation and it returned to the control level following rehydration. Serum Na level, osmolality, cortisol level and creatinine level increased significantly during food and water deprivation and returned to the control level after rehdration. In experiment 2, the effects of exposure of desert rams to solar radiation and chromium chloride (CrCl3.6H2O) supplementation on thermoregulation and blood constituents were evaluated in rams. Exposure to solar radiation did notinfluence the mean BW of rams significantly. The values of Tr and RR were significantly higher in rams exposed to radiation in the afternoon. Solar heat load was associated with decrease in PCV and Hb concentration and TLC. The treatment increased plasma glucose level and increased serum cholesterol level and decreased serum levels of total protein and albumin. A decrease in serum osmolality and serum insulin level occurred during exposure to solar radiation. Chromium supplementation decreased plasma glucose level and serum albumin level and increased serum total protein level. Chromium decreased serum total lipids and cholesterol levels and increased serum insulin level. Food and water deprivation inducedsignificant changes in the physiological responses of desert ewes. The results also indicate that desert rams can acclimatize on exposureto direct solar radiation. Cr supplementation may have beneficial effects in stressed sheep. The results were discussed and interpreted inthe light of findings reported in literature. The implications in environmental physiology as well as sheep welfare have been discussed.. LIST OF CONTENTS