Received: 04-10-2021 / Accepted: 10-01-2022
This study was conducted to evaluate the effects of dietaryfructooligosaccharides(FOS) and Bacillus subtilison immune response and disease resistance of red tilapia (Oreochromissp.). The experiment was randomly designed with 4 triplicated treatments including control; B.subtilis(107CFU/g); B.subtilis(107CFU/g)and 0,2% FOS; B.subtilis(107CFU/g)and 0,5% FOS. The samples were collected at the 2ndand 4thweek post-feeding and the 3rdday post challenge with Streptococcus agalactiae. The resultsafter 4 weeks of experiment showed that the total erythrocytes, leukocytes, monocytes, neutrophils, lymphocytes and lysozyme activity significantly increased (P <0.05) in treatmentsofB.subtilisand FOS supplementation in comparison tothe control treatment. After infection with S.agalactiae, a cumulative mortality of fish in treatments ofB.subtilisand FOS wassignificantly lower than thatof fish in the control treatment(P <0.05). In particular, the mortality ofB.subtilis107CFU/g + 0,5% FOS treatment was lowest (26.7%± 8.2%) and significantly differentwith other treatments(60 ± 6.7% và 46.7 ± 12.3%).The results indicated that the supplemented FOS and B.subtilisin the diet could stimulate the non-specific immune system of red tilapia and protect the fish from S.agalactiaeinfection.