Dietary lacto-sacc stimulates the immune response of gravid mud crab (Scylla olivacea)

Mud crabs have a functioning innate immune system. Probiotics have a considerable effect in improving immune responses in gravid mud crab. The current study investigated the influence of three lacto-sacc concentrations (T1=0 %, T2=1 %, and T3=1.5 %) in a 45 % protein and 12 % lipid meal on the immune response of gravid mud crabs. Three groups of wild gravid mud crabs (average weight: 122.33±1.53 g) were raised individually in bamboo spawning boxes at mangrove pens for 12 weeks. Wild gravid mud crabs (T4) were also caught from the river during the breeding season and tested to offer a more exact assessment of the effect of lacto-sacc. After a 12-week feeding study, T3 therapy resulted in the highest total hemocyte count levels (P < 0.05), followed by T2 and T1. The T3 treatment results in somewhat faster hemolymph clotting, although there is no significant difference among the treatments (P < 0.05). T3 treatments significantly improved immunological parameters (PO, proPO, and SOD enzyme) and survival (61.67±2.89 %) when challenged with Vibrio parahaemolyticus. In the challenge test, the immunological markers THC, PO, and proPO correlated positively, but hemolymph clotting time and mortality linked negatively. Furthermore, T1 was compared to an untreated wild gravid female mud crab (T4), and the results were almost identical. Thus, 1.5 % lacto-sacc is recommended for gravid mud crabs.