Supplementation of Bacillus velezensis S141 in feed as a probiotic enhances growth performance, pathogenic tolerances, and immune system in shrimp

In Litopenaeus vannamei aquaculture, infectious diseases pose significant challenges, leading to the exploration of alternative strategies for pathogen combat. This study examines the efficacy of Bacillus velezensis S141, supplemented in feed at various levels 10², 10⁴, and 10⁶ CFU/g, on immune responses, growth performance, and disease tolerances against the White Spot Syndrome Virus (WSSV), Vibrio parahaemolyticus (VP_AHPND), and Enterocytozoon hepatopenaei (EHP). The results indicated significant improvements in the weight gain (WG), average daily gain (ADG), and specific growth rate (SGR) of shrimp supplemented with B. velezensis S141 compared to the control group. Moreover, shrimp supplemented with B. velezensis S141 had significantly higher survival rates during post-WSSV infection. Co-injection with B. velezensis S141 secretion and WSSV significantly improved survival rates and reduced WSSV copy numbers in the gill, indicating enhanced tolerance to the WSSV infection. Administering B. velezensis S141 reduced cumulative mortality during the VP_AHPND challenge and EHP copy number compared to the control group. Furthermore, the gene expression analyses of immune-related genes in the Toll/IMD pathway (Toll, IMD, LYZ1, LYZ-C, PEN4, ALF1, Relish, NF-kappa, RPX, and DOME), JAK/STAT pathway (STAT and GILT), Vago pathway (Vago4, Vago5), CathC, and α2M showed significant upregulation in the group administered feed containing 10⁶ CFU/g of B. velezensis S141 compared to the control group in the gills. This study emphasizes the potential of B. velezensis S141 as a probiotic supplement in enhancing immune responses and disease tolerances against WSSV, EHP, and VP_AHPND in L. vannamei, providing promising prospects for sustainable shrimp aquaculture practices.