The influences of thermal stress on serum biochemical parameters of Iranian fat-tailed sheep and their correlation with triiodothyronine (T_3),thyroxine (T_4) and cortisol concentrations

摘要

In order to study the influences of thermal stress on serum biochemical parameters of Iranian fat-tailed sheep and their correlation with triiodothyronine (T_3), thyroxine (T_4) and cortisol concentrations, an experiment was conducted using 45 clinically healthy Iranian fat-tailed sheep. These animals were divided into three experimental groups: group I, 15 sheep at 4deg, group II 15 sheep at 21deg and group III 15 sheep at 40deg. Blood samples were taken from the jugular vein of all animals after 7 days' exposure to the appropriate environmental temperature. The concentrations of total protein, glucose, cholesterol, total lipid, calcium, inor ganic phosphorus, magnesium, creatine kinase, lactate dehydrogenase, triiodothyronine and thyroxine in cold stress conditions were higher than in heat stress; in contrast, the activities of aspartate aminotransferase and alanine aminotransferase were higher in heat stress conditions than in cold (p = < 0.05). Although there were no significant differences in the concentrations of blood urea nitrogen, triglyceride, alkaline phosphatase and cortisol at either heat stress or cold stress, the first three assays were significantly lower than in animals kept at optimum temperatures, with cortisol having significantly higher values. These results revealed that very hot and very cold conditions had a profound effect on serum biochemical parameters.