الفهرس 
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Abstract
This study was carried out to firstly, evaluate the effects of dietary fluoride supplementation on laying hens performance; secondly alleviation of fluoride toxicity in laying hens with aluminum and thirdly evaluate the effects of dietary selenium supplementation at different levels on productive performance of laying hens.
The 1000 and 1300 ppm fluoride (F) fed groups were significantly decreased body weight, feed consumption, egg number and egg mass compared to control fed group. Also, the plasma calcium and phosphorus were significantly decreased when laying hens fed a diet added 1000 or 1300 ppm F compared to other fed a control diet. The relative weight of liver, heart and gizzard of 1000 and 1300 ppm F fed groups were significantly higher than that of control fed group.
It could be concluded that the fluoride levels in plasma, liver, kidney and tissues were significantly increased when the 1000 and
1300 ppm F diet were fed. Also, the kidney contained more fluoride than the liver or muscle.
Additions of aluminum (AI) to the 1300 ppm F diets have no effect on performance parameters. Also, dietary AI tended to reduce the ionic F concentration in plasma. The addition of AI to 1300 ppm diet reduced the fluoride level in liver and kidney.
With respect to dietary selenium (Se) supplementation, it could be concluded that 5 and 10 ppm Se diets were significantly decreased body weight, feed consumption and egg production ratio compared to control diet. Also, egg quality was significantly affected by dietary Se. The concentration of Se in plasma, liver and kidney were significantly increased when hens fed a diet added Se.