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The probiotic effects of Saccharomyces cerevisiae and Aspergillus niger on the feeding efficiency, body composition, ammonia excretion, blood serum enzymes and the intestinal microbiota of juvenile beluga, Huso huso was investigated. The fish (31.8±2.81g) were randomly allocated into 12 oval tanks at a density of 30 individuals per tank with three replicates for each treatment,. The fish were fed either a basal diet (as control) or the diet supplemented with S. cerevisiae and A. niger (2×10⁶, 4×10⁶ and 6×10⁶ cells g^-1) for 8 weeks. The results indicated that the probiotic supplemented diet at 6×10⁶ (cells g^-1) significantly improved FCR and other nutritional indicators compared to the control treatment (p<0.05). Significant improvements (p<0.05) were also observed in ammonia excretion and blood serum enzymes between treatments. Total viable fungus and Lactobacillus spp. count were significantly improved in treatment compared to control (p<0.05). These results indicated that S. cerevisiae and A. niger improved feeding performance and blood serum enzymes of beluga.

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The effect of a probiotic containing five species of bacilli at four levels of 0 (control), 1×10⁶CFU/ml (T₁), 1×10⁷ CFU/ml (T ₂) and 1×10⁸CFU/ml (T ₃) per 100g of feed on the growth performances, resistance and survival of rainbow trout fry, Oncorhynchus mykiss (463±32 mg) were compared in a  60-days feeding trial. Growth parameters, such as ADG, SGR, RGR and TGC, were significantly enhanced (p<0.05) by the probiotic at all levels, and the performance in T₂ was significantly better than T₁. The fish under the probiotic treatments also showed higher resistance (p<0.05) to such Environmental stresses as alkaline pH, heat and ammonia (p<0.05). No significant difference in tolerance to acidic pH stress was observed between the control and treatments. In conclusion, the probiotic bacillus highly increased the growth performances, feeding efficiency, resistance and survival in rainbow trout fry.