Effects of adding two native bacterial strains (Lactococcus lactis and Weissella confuse) on growth performance, immune system response, and intestinal flora of juvenile great sturgeon (Huso huso)

The effects of adding 2 bacterial strains isolated from great sturgeon intestine (Lactococcus lactis and Weissella confuse) to pelleted diets, on growth performance, immune and biochemical parameters and intestinal flora of great sturgeon (Huso huso) were determined. The diets were prepared by spraying a mixture of 50 ml of physiological serum with 150, 300 and 450 mg probiotic powder per 1 kg of pelleted diets to make certain concentrations 1.5×109 cfu/g (T1), 3×109 cfu/g (T2), 4.5×109 cfu/g (T3) of two bacterial strains per kg of commercial diet, and control group (without probiotic). Initial fish mean weight (±SD) was 79.44 ±3.18g. At random 15 fish were stocked per each fiberglass tank (1m×1m×0.5m) with 300 liters of fresh water (0 ppt/L). Immune system, included the percentage of neutrophils in the T1 and T2 was significantly higher than the control and T3 (p <0.05). The percentage of lymphocytes in control and T3 was significantly higher than T1 and T2 (p <0.05). There was no significant difference in the percentage of eosinophils in treatments and control (P>0.05). Monocytes was in T3 significantly lower than T1, T2 and control (p <0.05). IgM and C3, were in experimental treatments significantly more than control (p <0.05). Lysozyme, C4 and ACH50 were in T1 an T2 significantly more than T3 and control (p <0.05). Colony count of aerobic and facultative anaerobic bacteria in the intestine of fish in the MRS medium, was in T1 and T2 significantly more than control and T3 (p <0.05).  Colony count of mentioned bacteria in the intestine of fish in the medium of TSA was in control significantly more than T1 and T2 (p <0.05). This indicates that, intestinal flora condition was worse in the control. Growth performance included, Biomass increase was in T1 more than control, T3 and T2 (p <0.05). The condition factor was in control more than other treatments (P <0.05). Food conversion ratio (FCR) was in T1 better than control and other treatments (P>0.05). There was no significant difference between treatments in terms of specific growth rate (SGR) and body weight gain (p>0.05). In sum it can be stated that, the two bacterial strains used had favorable effects on intestinal bacterial flora, immune and biochemical parameters and growth performance at two levels 150 mg (T1) and 300 mg (T2) especially in the T2.