Evaluation of the Use of Probiotics on Growth and Immunity of Tilapia in Recirculating Systems in Lagos State

Probiotics have gained considerable attention in aquaculture as alternatives to antibiotic growth promoters, with potential benefits for fish health, growth, and immune function. This study evaluates the effect of commercially available multi-strain probiotics supplemented at two levels (0.5 g/kg and 1.0 g/kg feed) on the growth performance, feed utilisation, and selected non-specific immune parameters of Nile tilapia reared in a recirculating aquaculture system at a private fish farm in Lagos State, South West Nigeria. Ninety tilapia with an initial mean weight of 15.6 g were distributed across nine tanks and fed experimental diets for eight weeks. Growth and feed utilisation parameters were computed at the end of the trial. Blood samples were collected for determination of lysozyme activity, serum bactericidal activity, and differential leucocyte count. Results showed that the 1.0 g/kg probiotic group recorded significantly higher specific growth rate and lower feed conversion ratio compared to the control. Lysozyme activity and serum bactericidal activity were significantly elevated in both probiotic treatment groups, indicating enhanced innate immune function. White blood cell counts were within normal ranges across all treatments. The study demonstrates that dietary probiotic supplementation at 1.0 g/kg enhances both growth and immune performance in Nile tilapia cultured in recirculating aquaculture systems under Lagos State commercial conditions.

Keywords: probiotics, Oreochromis niloticus, growth performance, immune response, recirculating aquaculture