Galactooligosaccharide effects as prebiotic on intestinal microbiota of different fish species

Manipulation of the gut microbiota toward potentially beneficial bacteria (probiotics) has beneficial effects on fish physiology and health. The effects of prebiotics on gut microbiota are species specific. The present study aimed at investigation of the effects of galactooligosaccharide (GOS) as prebiotic on intestinal microbiota of Caspian roach and Caspian white fish fingerlings. which are among the most economically valuable species in the Caspian Sea. The study was conducted in a completely randomized design with two set of experiment each of them include three treatments in triplicates in which 0 (control), 1 and 2% GOS were used in diet for 6 weeks. At the end of the period, changes in the intestinal microbiota, including total bacterial count, lactic acid count and lactic acid bacteria (LAB) levels and dominance of LAB in the intestinal microbiota, were measured by culture-based method. Dietary GOS had no significant effect on total bacterial count in both species (P < 0.05). The LAB levels in the intestinal microbiota in the treatments fed with prebiotics was significantly higher than the control group (P < 0.05). LAB bacteria showed the highest increase and dominance in treatments fed with 2% GOS. Also, the highest ratio of lactic acid bacteria to the total number of viable bacteria was observed in the treatment with 2% GOS treatment (P < 0.05). The results of this study indicated the possibility of alterations in the bacterial communities of Caspian roach and Caspian white fish fingerlings gut toward beneficial bacterial communities using GOS as prebiotic.