Impacts of dietary sodium alginate as a prebiotic on the oriental river prawn (Macrobrachium nipponense): A comprehensive analysis of growth, physiology, immunity, antioxidant, and metabolism

The effects of dietary sodium alginate supplementation on Macrobrachium nipponense were evaluated over a 60-day feeding trial, with emphasis on growth, hematological, immune-physiological responses, and metabolic characteristics. Juvenile prawns with an initial average weight of 1.47 ± 0.05 g were assigned to diets containing 0.0 (control), 0.5, 1.0, 2.0, or 4.0 g/kg sodium alginate. Among all the examined water quality indicators, dissolved oxygen (DO) was the only parameter that showed a statistically significant rise with increasing levels of sodium alginate supplementation, with the 4.0 g/kg group showing the maximum value of DO concentration (P < 0.05). Furthermore, growth metrics and survival rates (SR) were significantly enhanced in prawns receiving 2.0 and 4.0 g/kg sodium alginate compared to other treatments (P < 0.05). Hemato-biochemical indices generally decreased following sodium alginate supplementation, whereas levels of high-density lipoprotein (HDL) and low-density lipoprotein (LDL) were elevated (P < 0.05). Most immune parameters and antioxidant enzyme activities demonstrated positive modulation in response to the dietary intervention (P < 0.05), although glutathione peroxidase (GPx), acid phosphatase (ACP), and alkaline phosphatase (AKP) activities did not differ significantly among groups (P > 0.05). Diets supplemented with 4.0 g/kg sodium alginate notably enhanced digestive enzyme activities, promoted beneficial intestinal microbiota, and improved body composition (P < 0.05). Additionally, sodium alginate intake influenced the expression of genes associated with growth, immune function, and metabolism (P < 0.05). Overall, these findings support the dietary inclusion of 4.0 g/kg sodium alginate to optimize growth, physiological condition, and metabolic health in M. nipponense.