الفهرس 
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Abstract
This study was performed in Biochemistry and Chemistry of Nutrition Dept. Fac. Of Vet. Medicine, Mansoura University. This study was carried out on forty New Zealand white (NZW) weaned male rabbits aged 35 days and of 1.135kg average body weight. After the first week of acclimatization at the animal house Forty New Zealand White male rabbits (5 weeks old); The rabbits were distributed each in individual cage and thereafter were divided into 5 equal groups (8 rabbits each), the first group (control -ve) (G1) fed a control basal diet (without chromium and vitamin E supplementation and not subjected to heat stress). The second group (control +ve) (G2) fed the control basal diet (without chromium and vitamin E supplementation and subjected to heat stress). The other 3 groups were subjected to heat stress and fed on diets supplemented either with chromium (G3) as chromium picolinate; (600 µg/kg of diet), vitamin E (G4) ( -tocopherol acetate; 250 mg/ kg of diet) or both of them (G5) in which the experimental design were done over a period of 3 months. After the end of the experiment, blood (serum & whole blood) samples are collected from all the animals for the analysis of: cortisol, T3, T4, malondialdehyde (MDA), lipid profile and enzymatic (SOD and catalase) and non-enzymatic (GSH) antioxidant activities in the whole blood and tissue malondialdehyde contents and reduced glutathione level. Tissue samples (liver, brain and kidney) were collected for histopathological examination It is concluded that the effect of heat stress on some biochemical parameters are significantly decreased in SOD and catalase activities in erythrocytes, and decrease in reduced glutathione levels in erythrocytes and tissue. There was a significant decrease in serum HDL, LDL, T3, T4, total lipid, total cholesterol, triacyglycerol, total protein, albumin and globulin. There was a significant increase in the level of serum cortisol, MDA. The diet supplementation with chromium picolinate for heat stressed rabbits produces a significant decrease in serum and tissue MDA, cortisol. There are significant increases in SOD and catalase activities and glutathione level in erythrocytes and in serum T3, T4, HDL, LDL, total lipid, total cholesterol, triacyglycerol, total protein, albumin and globulin levels in comparison with heat stressed rabbits. The effect of vitamin E supplementation on some biochemical parameters shows significant increase in SOD and catalase activities and reduced glutathione level in erythrocytes and tissue. Also significant increase in serum total lipid, total cholesterol, triglycerides, LDL, and T3& T4 levels. The study advices that feeding on ration containing chromium picolinate and vitamin E to heat stressed rabbits will change the undesirable effect of heat stress. Like reduction in free radicals, increase antioxidants.