The effects of different levels of GroBiotic®-A on antimicrobial activity and some immune parameters of mucus of cultured juvenile beluga (Huso huso)

The mucus layer on the skin of fish contain a several of antimicrobial compounds that provide a first line of defense against fish pathogens. This study was conducted to evaluate the effects of different levels of prebiotic GroBiotic®-A on antimicrobial activity and some immune parameters of mucus of cultured juvenile beluga (Huso huso). For this purpose, four groups of beluga sturgeon with mean weight of 40.82± 5.8 g were raised for 8 weeks in fiber glass tanks (20 fish to each tank) and feeding with different levels of GroBiotic®-A with concentrations of % 0, % 0.5, %1.0 and % 2.0. At the end of trial, mucus was collected from the surface of the skin and its antibacterial activity against some common pathogenic bacteria was evaluated by disk diffusion and serial dilution methods. Results showed by increasing the concentration of GroBiotic®-A, significant diffirences in inhibition zone diameter, soluble protein content and alkaline phosphatase activity of mucus was observed in compare to control groups(P< 0.05). Similar results was observed in serial dilution method. MIC test showed a minimum concentrations of mucus ranged between 25 to 250 μg/l were able to inhibit the growth of the selected bacterial. Based on the results, using of GroBiotic®-A, especially at the level of 2.0%, in order to increased the antimicrobial activity, soluble protein content and alkaline phosphatase activity of mucus of farmed beluga was recommended.