The combination of Astragalus membranaceus and Lycium barbarum polysaccharides is superior to either alone in enhancing growth and health of grass carp (Ctenopharyngodon idellus)

This study investigated the potential effects of dietary Astragalus polysaccharide (APS) and Lycium barbarum polysaccharide (LBP), administered individually and in combination, in juvenile grass carp ( Ctenopharyngodon idella ). The primary goal was to determine whether their combination could elicit more profound benefits on overall health and productivity than either polysaccharide alone. Four iso-nitrogenous and iso-lipidic diets were formulated: a control diet, and diets supplemented with 0.1% APS, 0.1% LBP, or a combination of 0.05% APS and 0.05% LBP (AL). Following a 56-day feeding trial, all polysaccharide-supplemented groups significantly enhanced growth performance, digestive enzyme activities, and nutrient utilization compared to the control. Among them, the AL group achieved the highest final body weight and the lowest feed conversion ratio. Similarly, serum biochemistry was markedly improved by all polysaccharides, with the AL group exhibiting the most favorable profile of lowered triglycerides, glucose, and LDL-cholesterol, and elevated HDL-cholesterol. The antioxidant defense system was also significantly boosted across all supplemented groups, with the AL group showing the highest activities of key antioxidant enzymes and the lowest MDA level. This enhancement was consistent with transcriptional results, where the AL group most potently activated the Nrf2-Keap1 pathway and upregulated downstream antioxidant genes. In innate immunity, all polysaccharides elevated serum lysozyme and complement 3 levels, with the highest values observed in the AL group. Furthermore, all treatments shifted hepatic cytokine balance toward an anti-inflammatory phenotype, and the AL group induced the most significant upregulation of tgf-β1 and il-10 . These physiological improvements were functionally corroborated by a 7-day Aeromonas hydrophila challenge, in which the AL group exhibited the highest survival rate, significantly surpassing both individual polysaccharide treatments. The results indicate that the combination of APS and LBP is more effective than either polysaccharide alone in improving growth, digestion, antioxidant status, immune function, and disease resistance in grass carp. The combination represents a promising functional feed additive for sustainable aquaculture.