Impacts of Mannan oligosaccharides (MOS) on growth performance andgastrointestinal health of Nile tilapia (Oreochromis niloticus)

Objective: This study was undertaken to evaluate the potential role of Mannan oligosaccharides (MOS) on growth performance, liver and intestine tissue morphology, and gut microbiota of Nile tilapia (Oreochromis niloticus).
Design: Controlled study.
Animals: Three groups of Nile tilapia.
Procedures: Three diets were formulated to contain 0 % of MOS 500 (MOS) as control (control), 0.05% of MOS plus adding MOS into water as well at level of 12.5 mg/l (MOS (feed +water), and the third group MOS was added only to water (MOS water) at the same level, and fed to Nile tilapia for 6 weeks.
Results: Simultaneous water and feed additives with (MOS feed+water) at (0.05% of feed + 12.5 mg/l water) caused a significant increase in growth parameters (initial and final weight, weight gain (WG), specific growth rate (SGR), feed conversion ratio (FCR) and condition factor (k), when compared to both MOS added only in tank water (MOS water) and control groups. In addition, MOS in both treatment types increased survival rates significantly compared to the control. Polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE) analysis showed that a single species or species that contained chemically equivalent DNA dominated the intestinal tract of all Nile tilapia regardless of dietary treatment. While MOS had no adverse effect of intestinal histology, an increase in the villi length was recorded.
Conclusion and clinical relevance: Collectively, our results indicate that MOS added to feed and water could be used to enhance the growth performances, increase the survivability and exert beneficial effects on the gut microbiota of Nile tilapia.