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This study was conducted to evaluate the effects of dietary autochthonous Saccharomyces cerevisiae and Aspergillus niger on the growth performance, survival rate, ammonia excretion, immune response and the intestinal microbiota of juvenile beluga sturgeon (Huso huso). Beluga juveniles with average (±SD) weight of 31.8±2.81 g were randomly allocated into 12 oval tanks (1000 l) at a density of 30 fish per tank and triplicate groups and were fed either with a basal control diet (no supplemented with probiotic) or with the basal diet supplemented with S. cerevisiae and A. niger (2×106, 4×106 and 6×106 cells g-1). After 8 weeks of feeding on the experimental diets, growth factors, survival rate, ammonia excretion, immunity parameters and gut microbiota were measured. The results indicated that dietary supplementation of 6×106 (cells g-1) S. cerevisiae and A. niger significantly improved growth indicators, survival rate, immune parameters and ammonia excretion compared to the control treatment. Additionally, total autochthonous intestinal fungus probiotic and Lactobacillus spp. counts were affected by dietary treatment. The results showed that dietary supplementation of S. cerevisiae and A. niger (6×106 cells g-1) had positive effects on growth and immunity factors in cultured juveniles beluga.

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In this study, the effects of protein restriction in the diet and re-feeding with complete diet on growth performance and body composition of fingerling common carp (Cyprinus carpio) were studied during 8 weeks. Common carp fingerlings with an average initial weight (20/09 ± 0/07) in seven experimental groups were fed with three replications. Treatment A: 8 weeks were fed diet with 32% protein (control group), for treatments of B, C, D, E, F and G respectively the protein restriction phase was considered one week, two weeks, three weeks, four weeks, one week within three weeks of feeding the diet containing 16% protein as dietary protein restriction Highest final weight, body weight increase, percentage of body weight gain, feed conversion efficiency and specific growth rate was observed in group C and the lowest was observed in group E. Highest feed conversion ratio was observed in treatment C which significantly higher than treatment D and E (p<0/05). Highest protein efficiency ratio was observed in treatment F which showed no significant difference between treatments C and G (p>0.05) but with other treatments were significantly different (p<0/05).none of the treatments ash did not show a significant difference together (p>0/05).Highest of the moisture content of the carcass observed in treatment E which not significantly different with treatments F and G (p>0/05) but showed significant differences (p<0/05) with other treatments. Also highest carcass protein and fat was levels in treatment D and F were observed. In the end it can be concluded that the more protein during long periods of limitation, the ability of fish to compensate for the slowdown, but will be less than the length of the limitation period is less protein, the better fish can compensate for the lack.