Study of different levels of Lactobacillus spp and Bacillus spp probiotics inoculated in larvi-culture system on larval quality indices of the western white leg shrimp (Litopenaeus vannamei)

Strengthen defense mechanisms with immune system stimulants like probiotics, it is a good way to prevent diseases and increase the efficiency of reproduction and breeding in fishers. Bacillus and Lactobacillus are a group of gram-positive bacteria and previous studies have shown that the use of these bacteria improves immunity and reproductive factors in aquaculture. In this study, the combined effects of optimal concentrations of two probiotics, Bacillus and Lactobacillus, on qualitative indicators including: larval stage index (LSI), larval condition index (LCI), larval dry weight, larval survival, Simultaneity of larval maturation to post larvae, time of emergence of first post larvae, duration of larval period and salinity and formalin stress tests in order to investigate Improvements in qualitative growth indices and immune system of Vannami shrimp larvae were examined. For this purpose, two concentrations of 3×105 (B1) and 6×105 (B2) CFU/g from of bacterial suspension mixtures Bacillus probiotic and two concentrations of 3×106 (L1) and 6×106 (L2) CFU/g from of bacterial suspension mixtures probiotic Lactobacillus in combination includes: B1L1, B1L2, B2L1 and B2L2 were added to the water of Vannami shrimp larval reservoirs. The results showed that the larval quality indices at different levels of combined probiotics differed significantly from the control treatment and the best results were at level 4, respectively: Survival was 61±3.41, dry weight was 143±5.48, larval maturation reached was 1.26±0.02, the time of emergence of the first larval post was 7.5±0.82, the length of the larval period was 8.4±0.15. The two indices of larval stage index and larval status index were examined on the third, sixth and ninth days. The results showed a significant difference between the control group and other combination treatments, and no significant difference between combination treatments for both indices. Salinity and formalin stress tests also showed significant differences between the control group with different levels of combined probiotics for all indicators. Finally, the most important quality indicators of larvae 31% increase in survival, 30% increase in dry weight, 33.8% improvement in the synchronization index of larvae reaching post-larvae, 14.7% decrease in the time of emergence of the first post-larvae and 20% reduction in larval duration was observed at level 4.