To evaluatethe effects of supplementing diets of growing Japanese quails (n=450; 7 days old) with chromium (Cr) yeast and / or mannan oligosaccharides (MOS) on productive performance, carcass traits and the immune system are reported. Diets were a basal diet (control) or the basal diet supplemented with 600 mg Cr-yeast/kg (Cr 1), 1200 mg Cr-yeast/kg (Cr 2), 1.0 g MOS/kg, Cr 1 + MOS or Cr 2 + MOS. Quails fed Cr 1, MOS or Cr 1 + MOS diets had similar final live body weight and weight gain, with both groups being higher than the control. Feed conversion tended to be improved with dietary supplements. Carcass traits did not differ among treatments. Primary and secondary humoral immune responses of quails fed the supplemented diets were higher than the control. Plasma total proteins and triiodothyronine were increased, while plasma total lipids and cholesterol were decreased by the supplements. In conclusion, dietary supplementation with Cr yeast (600 mg/kg) and / or mannan oligosaccharides(1.0 g) improved productive performanceand immunity and reduced total cholesterol ofgrowing Japanese quails. Manuscript profile

The aim of the present study was to investigate the possibility of improvingproductive performance and immunity of growing Japanese quailreared during summer in Egypt by supplementing the diets with organic zinc (Bioplex zinc) and prebiotic (mannan oligosaccharides). Diets were a basal diet or the basal diet supplemented with 20 mg Bioplex zinc (3.0 mg Zn) (Zn1), 40 mg Bioplex zinc (6.0 mg Zn) (Zn2), 1.0 g prebiotic (P), P + Zn1 or P + Zn2. Ambient temperature and relative humidity ranged between 34 to 36 ˚C and between 45 to 51%, respectively. No significant difference was observed in body weight, body weight gain, feed intake, feed conversion and mortality of the treated quails when compared to the control group. The effect of treatments on the carcass traits and relative weights of the lymphoid organs and thyroid gland was not significant. The primary and secondary immune responses were the highest in the treated quails. The results showed that plasma total protein of the (P) and (P+Zn2) treated quails increased significantly when compared to the control group. The level of plasma total lipids and cholesterol decreased significantly (P<0.05) in quails fed the supplemented diets. No significant change was observed in the plasma AST and ALT enzyme activities and triiodothyronine concentration. It is concluded that, supplementing diets of growing Japanese quailsreared during summer in Egypt with 20 or 40 mg Bioplex zinc/kg each alone or in combination with 1.0 g/kg prebiotic (mannan oligosaccharides) had no significant effect onproductive performancebutimproved their immune response. Manuscript profile