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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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In a completely randomized experiment, the effect of Daphnia magna meal on growth performance and carcass composition of rainbow trout (Oncorhynchus mykiss) larvae (body weight 0.538±0.197 g) was evaluated for a period of 60 days. Five diets with the same protein content (crude protein 52.70%) were prepared, including two diets containing fermented daphnia meal T₁ (20%), T₂ (30%), two diets containing raw meal T₃ (20%) and T₄ (30%), and a basal diet without daphnia meal as the control. The bacterial species used for fermenting included five commercial probiotic species. Fermented daphnia meal brought about significantly higher growth and the lowest feed conversion ratios, viz. T₁ (1.27 ± 0.35) and T₂ (1.31 ± 0.46), in comparison with T₃ (1.38 ± 0.37), T₄ (1.41 ± 0.42) and the control (1.84 ± 0.69) (p<0.05). The result of carcass composition analyzes showed that the highest protein percentage (68.23 ± 0.48%) was in T₂ and the highest percentage of fat and energy (11.26 ± 0.50% , 4761.63 ±48.88 Cal g^-1) were in T₄ (p<0.05). The overall results of this experiment indicated that daphnia could be considered as a suitable partial protein source in rainbow trout larval feed.

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 This research was conducted to determine the effects of garlic extract as feed supplement on the growth performance, body content, blood indicators and culture water quality of rainbow trout (Oncorhynchus mykiss) under stress ammonia. A total number of 156 fish (Average weight 18.37±1.43g and total length 12.27±0.52cm) were reared in twelve 50-L tanks for 60 days (First period: 50 days of feeding with different levels of garlic extract) and (Second period: 10 days under ammonia stress of 0.024 mg /L). Experimental included adding different levels of extract to base food, 0, 0.5, 1 and 1.5% (control, A1, A2 and A3, respectively). The growth performance was significantly higher in fish fed garlic extract supplementation than control. There was a significant difference in feed conversion ratio between different treatments, so that was obtained the lowest in A2 and the highest in control. Protein, immunoglobulin and cortisol concentrations were significantly affected by different levels of garlic. The end of the experiment period, the fish were kept in a close recirculation system for 24 hours. Water sampling was carried out every 4 hours. Water ammonia increased from 16 to 24 hours of the test. At the end of the experiment (time 24), the highest ammonia was obtained in treatment A3 (0.43). In general, the results showed that the addition of 1 to 1.5% garlic extract improved the growth performance and immune response in rainbow trout, while in the recirculation system, the water quality of the rearing environment was better in the control treatment.