The present study amid to evaluate the effect of feeding Silver Montazah parents reared in open system house during winter season on different selenium sources and levels on the fertility of cocks, performance and mortality % of hatched chicks. The examined two selenium sources were nano selenium (Nano-Se) and sodium selenite (SS), and the three supplemental levels of each source were 0.10, 0.25 and 0.40 ppm. 180 females and 90 males of Silver Montazah chickens divided into 6 treatments of three replicates of each. Males and females located in separate battery cages in open system house. Semen characterization was carried out, then hens were artificially inseminated by semen from cocks with the same dietary treatment. A total number of 90 eggs/treatment were incubated and fertility and hatchability were calculated. Hatched chicks fed on control diet containing 0.10 mg SS /kg diet up to 2 wks of age then chicks of each treatment received the same Se treatments of their parents. Growth performance of chicks was recorded up to 8 wks of age. The obtained Results showed that: - Using Nano Se improved semen ejaculate volume, sperm motility, growth performance of hatched chicks during first 2 wks of age and their dressing % and PCV% at 8 wks of age, also it improve significant the activities of antioxidant system and liver functions. , using levels 0.25 mg Se/kg enhance the overall semen quality, fertility and hatchability chick performance and their physiological statues.

- The overall results of all experiment treatments showed superior effect of using Nano-Se at level 0.25 mg Se /kg diet to enhance the overall reproductive performance of cocks and growth and physiological status of their hatched chicks up to 8 wks. In addition, the examination of blood cells and plasma biochemical measurements showed positive effect on antioxidant system and overall immune status. Based on the obtained results we could recommend using 0.25 mg Nano Se/kg diet to enhance the reproductive performance of Silver Montazah cocks and decrease mortality rate of growing chicks during winter season.