Host-associated probiotics boosted mucosal and serum immunity, disease resistance and growth performance of Nile tilapia (Oreochromis niloticus)

The investigation was conducted to evaluate the possible effects of singular or combined administration of host-associated probiotics (Lactobacillus plantarum N11 and Bacillus velezensis H3.1) on several innate-immune parameters, disease resistance, and growth performance of Nile tilapia, (O. niloticus). Tilapia fingerlings were assigned for te following diets: Diet 1 (0 - control), Diet 2 (107 CFU g−1B. velezensis H3.1), Diet 3 (108 CFU g−1 L. plantarum N11), and Diet 4 (107 CFU g−1B. velezensis H3.1 + 108 CFU g−1 L. plantarum N11). At days 15 and 30 post feeding, skin mucus and innate immune parameters as well as growth performance were collected. The challenge test was conducted at the end of feeding trial (i.e 30 days post feeding). The results showed that dietary administration of Lactobacillus plantarum N11 and Bacillus velezensis H3.1 resulted in significant increase skin mucus lysozyme and peroxidase activities of the fish (P < 0.05). However, no significant difference was detected among supplemented groups (P > 0.05). For serum immunity, serum lysozyme activity of fish fed probiotics diets was significantly higher than the control group, except for fish fed B. velezensis H3.1, where no significant was observed when compared with the control (P > 0.05). Likewise, serum peroxidase, alternative complement, phagocytosis, and respiratory burst activities were significantly higher in treated groups compared to the control (P < 0.05). Also, the relative percent of survival (RPS) in L. plantarum N11 and B. velezensis H3.1, L. plantarum N11, and B. velezensis H3.1 treatments were 58.33%, 54.17%, 41.67%, respectively. Nonetheless, no significant differences were observed among supplemented groups regarding RPS (P > 0.05). However, dietary administration of host-associated probiotics remarkably improved the growth performance, specific growth rate, weight gain, final weight, and feed conversion ratio (P < 0.05). The present results indicated that singular or combined administration Lactobacillus plantarum N11 and Bacillus velezensis H3.1 can be considered as beneficial feed additives for Nile tilapia.