Effect of treatment with probiotics as water additives on tilapia (Oreochromis niloticus) growth performance and immune response.

A feeding trial was conducted for 40 days to delineate the effect of treatment with probiotics as water additives on tilapia (Oreochromis niloticus) growth performance and immune response. About 360 juveniles were randomly distributed into four treatment groups, each with three replicates. Different probiotics (T-1, Bacillus subtilis B10; T-2, Bacillus coagulans B16; T-3, Rhodopseudomonas palustris G06) were added to the water of tanks at final concentration of 1 x 10(7) cfu ml(-1) every 2 days, with no probiotic added to control tanks. At the end of the feeding trial, fish treated with B. coagulans B16 (T-2) and R. palustris G06 (T-3) had significantly (P < 0.05) higher final weight, daily weight gain, and specific growth rate compared with those treated with B. subtilis B10 (T-1) and those without probiotics (control). The highest (P < 0.05) content of total serum protein was found in T-2 compared with that in T-1, T-3, and the control. However, albumin concentration and albumin/globulin ratio were not affected by the probiotics treatments. Compared with the control, probiotic supplementation remarkably improved activities of superoxide dismutase and catalase (P < 0.05). T-2 fish exhibited higher average myeloperoxidase activity than the control, T-1, and T-3 groups. Regarding serum lysozyme content in tilapia, assays showed no difference (P > 0.05) among the treatment groups. Furthermore, probiotics treatments remarkably increased respiratory burst activity compared with control, with T-2 showing higher values than T-1 and T-3. This indicated that treatment with probiotics, B. coagulans B16 and R. palustris G06, as water additives could be used to enhance immune and health status, thereby improving growth performance of O. niloticus.