Modulating gut microbiota and digestive enzyme activities of Artemia urmiana by administration of different levels of Bacillus subtilis and Bacillus licheniformis

The aim of this study was to evaluate the effects of Bacillus subtilis and Bacillus licheniformis on growth, gut microbiota, and digestive enzyme activities of Artemia urmiana. Three diets containing 10(2) (T-1), 10(4) (T-2), 10(6) (T-3) CFU of probiotics/g feed, and a control diet (C) without probiotic were used through a completely randomized design (treatments with triplicates). Twelve plastic tanks with the capacity of 60- l and density of 20 nauplii/ml were used and the trial continued for 15 days. Results showed that probiotics significantly increased the total length of A. urmiana (P < 0.05). Although the total aerobic gastrointestinal bacteria count showed no significant differences among the treatments, the total Bacillus count significantly increased in experiments (P < 0.05). The ratio of TCBS to total aerobic bacteria count was significantly lower in T-1 (0.31 +/- A 0.05), T2 (0.27 +/- A 0.15), and T-3 (0.25 +/- A 0.05) compared to the control (0.76 +/- A 0.34) (P < 0.05). The probiotics were able to increase the protease and amylase activities (P < 0.05). No significant effect on lipase activity. The study determined T-2 and T-3 as the most effective treatments for improving growth, bacterial flora, and digestive enzyme activities. As less probiotic needed in T-2, using 10(4) bacteria per g diet is recommended for rearing Artemia up to the maturity stage.