The modulatory effect of mannanoligosaccharide on oxidative status, selected immune parameters and tolerance against low salinity stress in red sea bream (Pagrus major)

The current study evaluated the effects of dietary mannanoligosaccharide (MOS) on red sea bream (Pagrus major) performances. Fish fed five dietary levels of MOS at 0, 0.5, 1, 1.5 or 2 g/kg for 60 days. The results showed that MOS supplementation significantly increased the final body weight, weight gain, and specific growth rate with decreased feed conversion ratio especially in fish fed 1.5 g per kg diet (P < 0.05). The hematocrit level was significantly increased in fish fed dietary MOS at 1.5 g/kg while, total serum protein increased in fish fed MOS at 1 or 1.5 g/kg in comparison with the control. However, glutamic pyruvic transaminase (GPT) was significantly decreased in fish fed dietary MOS at 0.5, 1 or 2 g/kg when compared to the other groups. The combined pattern of biological antioxidant potential (BAP) and reactive oxygen metabolites (d-ROMs) indicated that fish showed improved antioxidative response with higher BAP value in fish fed MOS at 0.5, 1 or 2 g/kg than the control group. The activities of lysozyme, bactericidal and peroxidase in serum and mucus of fish fed MOS diets increased over the control. Additionally, blood nitro blue tetrazolium assay (NBT) and alternative complement pathway (ACH50%) were increased significantly in fish fed on MOS over the control regime. Interestingly, fish fed MOS at 0.5, 1 or 2 g/kg exhibited higher tolerance against low salinity stress as compared to the control group. In conclusion, MOS administered as feed supplement at 1.5–2 g/kg enhances the growth performance, rises the levels of serum and skin mucus immune responses and increases the activity of antioxidant enzymes in red sea bream. Keywords: Mannanoligosaccharide, Serum immunity, Mucus immunity, Oxidative status, Red sea bream, Stress resistance