Effects of mannan oligosaccharide and synbiotic supplementation on growth performance and immune response of Gilthead Sea Bream (Sparus aurata) before and after thermal stress

In this study, the effects of mannan oligosaccharides (MOS) and a commercial synbiotic (Biomin)-supplemented diets on growth and survival performance of gilthead sea bream after eight weeks culture at 27oC and then ten days at 34oC were evaluated. Before heat stress, the Biomin supplemented diet significantly increased the number of red blood cells (RBC) and eosinophils of the fish. The MOS-supplemented diet increased the haematocrit, haemoglobin, lymphocytes, white blood cells (WBC) and monocytes significantly. Total immunoglobulin was significantly higher in both supplemented diets in contrast to the control group. After thermal stress, experimental diets increased the monocyte counts, lysozyme, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) of the fish significantly, also the lowest concentration of cortisol was observed in the fish fed with Biomin supplemented diet. Gene expression profile showed a significantly higher expression of innate immune genes (il-1 beta, ghr-1, tnf-alpha and igf-1) in fish fed with Biomin and MOS supplemented diets. However, after thermal challenge, inflammatory response was significantly lower the fish fed with the supplemented diets. According to our results, MOS- and Biomin-supplemented diets enhance the immune health status of the gilthead sea bream during thermal stress.