The effects of dietary supplementation with Enteromorpha prolifera polysaccharide on the growth, immunity, and antioxidant capacity of spotted sea bass Lateolabrax maculatus

Abstract

The aim of this study was to investigate the effects of dietary supplementation with Enteromorpha prolifera polysaccharide (EPP) on the growth, antioxidant, and immune capacity of spotted sea bass Lateolabrax maculatus. EPP were added to the diet of spotted sea bass in gradients (0, 3, 6, 9, 12, and 15 g/kg). A total of 540 similarly sized and healthy spotted sea bass were randomly divided into 6 groups and fed the corresponding diet for 49 days. The results showed that compared with not adding an EPP group, the WGR at 9 g/kg EPP supplemental level was significantly increased (P < 0.05); the SGR at 12 g/kg EPP supplemental level was significantly increased (P < 0.05). In addition, the supplementation of EPP could improve the immunity of spotted sea bass to a certain extent, but excessive supplementation may cause immunosuppression. The addition of 6 and 9 g/kg EPP significantly increased the activities of IgM, C3, and ACP in serum. After the increase in supplemental levels, the relevant immune indexes were observed to be significantly decreased. On the other hand, dietary supplementation with EPP showed disorganized results in terms of antioxidant capacity. Transcriptome analysis showed that in the liver, major differential genes were enriched in apoptosis-related pathways, and the related HSP90 gene was downregulated. In the head kidney, differential genes were mainly enriched in immune-related pathways, and the related FTH1 and LST8 genes were observed to be upregulated. Therefore, EPP may regulate the immune capacity of spotted sea bass by regulating immune-related pathways and apoptosis-related pathways.