The main objective of this study was aimed to investigate the effects of different ambient temperature {normal temperature (NT) and heat stress (HS) conditions} and dietary supplementation of different selenium (Se) source (inorganic , organic and Nano Se) on some productive performance and physiological parameters for Sinai chickens during growth period and A total of 198, 8-wks-old of Sinai chickens were used and randomly distributed into two experimental groups (NT& HS), and then each group was divided into three sub-groups (inorganic , organic and Nano Se) in a factorial design (2x3). Chickens fed diet naturally contaminated with Aflatoxin (AFB1),7.50 μg/kg DM.
The results indicated that heat stress resulted in a significant decrease in body weight and gain, feed intake and feed conversion. Lymphocytes (L) cells (%), plasma total protein and albumin were significantly decreased for chickens reared under heat stress, however, hemoglobin (Hb) concentration, white blood cells count, eosinophils cells (%), monocytes cells (%),globulin, calcium and phosphorus were not significantly affected. Moreover, a significant increases were recorded for red blood cells (RBC) count, heterophils (H) cells (%) , H / L ratio, plasma total antioxidant capacity (TAOC) and heat shock protein 70 for Sinai chickens reared under heat stress than those reared in thermo neutral during all the experimental periods.
Supplementing different selenium sources to the diet had no significant effect on body weight and gain, rectal temperature and respiratory rate, albumin, calcium, phosphor and heat shock protein 70 for Sinai chickens than those fed the control diet. Moreover, feed intake, plasma H (%), and H / L were significantly decreased as a result of supplementing Nano selenium to the diet during the periods of 12-16 and 8-16 wks of age than the control. While, feed conversion was significantly improved by supplementing different sources of Se to Sinai chickens diet than the control. Significant increases were recorded in RBC count, Hb concentration and L cells (%), total protein, globulin and total antioxidant capacity for Sinai chickens fed diet supplemented with Se as compared with those fed the control diet. These results indicated that heat stress severely reduced productive and physiological performance for Sinai chickens, whereas the productive and physiological performance was improved by dietary Se sources supplementation under heat stress.