الفهرس 
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Abstract
The objective of this investigation was to study Productive performance and physiological responses of laying hens treated with Nano-Selenium under heat stress conditions. One hundred and fifty (150) 21-weeks-old purpose breeding hens of ISA White strain were housed in individual cages in a semi-open house. Birds were distributed randomly into five treatments of 30 females. The 1st treatment was fed a control inorganic selenium (sodium selenite) diet containing 0.3 mg inorganic-Se/kg diet. The 2nd, 3rd, and 4th treatments were fed the Nano-Selenium diet supplemented with 0.1, 0.2 and 0.30 mg Nano-Se/kg diet. The 5th treatments were fed the organic-Se (selenomethionine, as Se-yeast Selplex® Alltech, Nicholasville, USA) respectively. Feed and water were provided ad-libitum throughout the experimental period (21–34 weeks of age). Artificial light was used beside the normal day light to provide 16 hour/ day photo period. The inorganic and organic forms of examined Se were obtained from commercial suppliers while both powder and liquid forms of Nano Se
were prepared immediately before starting feeding phases of the experiment. The prepared 80 nm Se Nano-particles were synthesized by chemical reduction method and characterized by Transmission Electron Microscope, X-ray diffraction and spectrophotometry. Different Se levels of the organic, inorganic, and Nano-Se form did not significantly (P≥0.05) affect egg weight, feed intake, and most of egg quality traits. Hen-day egg production percentages, egg number, egg weight, egg mass, and feed conversion ratio (FCR) were significantly (P≤0.05) improved between differences by Nano-Se supplementation compared with hens fed the control in layer diets. Body weight did not induce any significant differences among treatments. (P≤0.05) increased with supplementation levels of (0.1, 0.2, and 0.3 mg Nano-Se/ kg diet) compared the control. In addition supplementation Nano-Se significantly (P≤0.05) increased total protein, globulin and serum transaminase (GPT and GOT), while, total cholesterol were significantly (P≥0.05) decreased. Total antioxidant capacity concentration was increased significantly by supplementation source selenium as compared to the control group. The highest of TAC may indicate the increase of antioxidant status in the birds received 0.2 mg Nano Se/kg diet by (43.8 %), as compared the control. In conclusion, under hot desert conditions, hens fed Nano-selenium at a level of 0.2 mg Nano-Se/ kg diet might alleviate the drastic effect of heat stress and it’s positively reflected on productive performance and egg shell quality, without any harmful effects on hematological parameters.