Aim: To assess Pediococcus acidilactici as a dietary supplement for on-growing red tilapia (Oreochromis niloticus).
Methods and results: Tilapia were fed either a control diet or control diet supplemented with Ped. acidilactici at 10(7) CFU g(-1) for 32 days. Ped. acidilactici colonized the intestinal tract and significantly affected the intestinal microbial communities. PCR-DGGE revealed direct antagonism of gastric Ped. acidilactici with an endogenous uncultured bacterium during a period of reverting to nonsupplemented feeding. Light microscopy revealed that gut integrity and leucocyte levels were unaffected by Ped. acidilactici; however, blood leucocyte levels and serum lysozyme activity were elevated after 14-days' feeding. No significant improvements in growth performance were observed at the end of the trial (day 32), but survival was significantly higher in the probiotic group.
Conclusions: The study demonstrates that oral supplementation of Ped. acidilactici modulates intestinal bacterial communities in on-growing red tilapia and also stimulates some aspects of the nonspecific immune response.
Significance and impact of the study: To our knowledge this is the first study assessing the effects of probiotics on the gut microbiota of tilapia using culture-independent methods. Such methods are crucial to understand the mechanisms which underpin and mediate host benefits.
© 2010 The Authors. Journal compilation © 2010 The Society for Applied Microbiology.