A total number of 300 unsexed 7 d old Sasso chicks were randomly divided among 5 dietary treatments with 6 replicate cages per treatment and 10 chickens per cage, assigning experimental unit to investigate the effect of either live yeast of Saccharomyces cerevisiae (SC) or Mannaoligosaccharide (MOS) as a natural growth promoters on blood parameters, carcass characteristics and immune response. Dietary treatments were: 1st group fed a commercial basal diet without supplementation and served as control, the 2nd and 3rd groups fed basal diet supplemented with 0.1 and 0.2% of SC, and the 4th and 5th groups fed basal diet supplemented with 0.25 and 0.5g of MOS/kg. Results showed that treated groups had significantly greater body weight (BW), body weight gain (BWG), economical efficiency as well as higher values of nutrients digestibility than the control group. All treatments decreased serum AST, ALT, urea, creatinine, serum total lipids, triglycerides, cholesterol, LDL and increased glucose, T3, T4, TAC, GSH, GPX, SOD, RBC's , WBC's, total protein, globulin, phagocytic activity, phagocytic index, IgG, INFγ, IL2 and IL10 compared to control. Supplementation of SC or MOS increased significantly percentage of dressing and decreased abdominal fat compared to control. Moreover, SC or MOS decreased bacterial count of the digestive system compared to control group. In conclusion, both Saccharomyces cerevisiae and mannan oligosaccharide could be used safely as natural growth promoters to improve growth performance and immune response of Sasso broiler chickens.
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