http://http://dspace.unitus.it:80 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. 2013-06-18T06:32:29Z http://hdl.handle.net/2067/1557 Title: Effect of dietary alginic acid on juvenile tilapia (Oreochromis niloticus) intestinal microbial balance, intestinal histology and growth performance Authors: Merrifield, Daniel L.; Harper, Glenn M.; Mustafa, Sanaa; Carnevali, Oliana Abstract: The aim of the present study was to assess the effect of a commercial alginic acid source (Ergosan) on tilapia Oreochromis niloticus intestinal microbial balance, intestinal morphology, and growth parameters. Fish were fed a basal control diet or the basal diet plus a source of alginic acid (5 gkg-1 Ergosan; Schering-Plough Aquaculture, UK) for 9 weeks. At the end of the trial, light and electron microscopy demonstrated that the morphology of the intestinal tract at the gross and ultra-structural level was not affected by dietary alginic acid inclusion. Both groups of fish displayed healthy, normal morphology with no signs of disease, cell or tissue damage. Intestinal epithelial leucocyte infiltration was not affected by dietary alginic acid. Molecular bacterial profiles derived from PCR-DGGE illustrated highly similar microbial communities (both within the lumen and associated with the intestinal mucosa) in the respective treatment groups. Microbial ecological parameters (e.g. species diversity and richness) also remained unaffected. Although not significant, trends towards elevated survival and body protein content were observed in the alginic acid-fed fish. These results are suggestive that alginic acid does not adversely impact the indigenous gastrointestinal microbial balance and subsequently does not impact upon the epithelial brush border integrity. Validation of non-detrimental impacts of immunostimulatory products on gastric microbiota and epithelial integrity should be pursued in future studies as maintaining microbial balance and epithelial integrity is essential for proper gut functionality. Description: L'articolo è disponibile sul sito dell'editore HTTP://www.springerlink.com 2010-12-31T23:00:00Z http://hdl.handle.net/2067/1554 Title: The effect of Pediococcus acidilactici on the gut microbiota and immune status of on-growing red tilapia (Oreochromis niloticus) Authors: Ferguson, R.M.W.; Merrifield, Daniel L.; Harper, Glenn M.; Rawling, Mark D.; Mustafa, Sanaa; Picchietti, Simona; Balcàzar, Josè Luis; Davies, Simon J. Abstract: 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 107 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. Description: L'articolo è disponibile sul sito dell'editore http://onlinelibrary.wiley.com/ 2009-12-31T23:00:00Z