Effects of sodium butyrate dietary supplement on some haematological parameters, immunity and intestinal microbiota and response to stocking density stress of young beluga (Huso huso)

The aim of this study was to investigate the physiological response of young beluga to different levels of sodium butyrate in the diet. For this purpose, 360 young beluga (average weight of 15 ± 0.56 g) with 6 experimental diets containing 0, 0.1, 0.2, 0.3, 0.4 and 0.5% sodium butyrate were fed for 8 weeks. The number of red blood cells (RBC) and MCV, MCH and MCHC indices were significantly higher in the 0.3% treatment than in the other treatments (p <0.05). The number of white blood cells (WBC) and the amount of hemoglobin and hematocrit in fish fed with 0.3% sodium butyrate in the feed were higher than other treatments, although there was no significant difference with the treatment of 0.4% and the control group (p >0.05). Lysozyme activity and IgM level in 0.3% treatment was significantly higher than other treatments (p <0.05). Cortisol and glucose levels in fish fed diets containing 0.3% sodium butyrate increased slightly less than other groups after acute density stress and a significant difference was observed between treatments (p <0.05). Overall, this study indicates that including 0.3% sodium butyrate in the diet of young beluga can improve fish health, innate immune response and resistance to density stress.