A comprehensive comparison of single- and composite-seaweed feeds on growth performance, lipid metabolism, and immune function of large yellow croaker (Larimichthys crocea).

INTRODUCTION

The large yellow croaker (Larimichthys crocea) is an economically important fish species in China, yet its quality and value are compromised by excessive fat deposition induced by high-fat diets under high-density aquaculture. Our previous study noted the lipid-regulating potential of individual seaweed components like fucoidan and kelp (Saccharina japonica) powder, the synergistic effects of composite seaweed feeds remain underexplored.

METHODS

This study investigated the effects of 3% Neoporphyra haitanensis compared with its control feed (CM1), and two composite seaweed feeds (FNKM1: 1% kelp + 1% N. haitanensis + 0.1% fucoidan; FNKM2: 2% kelp + 2% N. haitanensis + 0.2% fucoidan) compared with the control feed (CM2) over an 8-week feeding trial.

RESULTS AND DISCUSSION: The results showed that single N. haitanensis supplementation, despite limited growth promotion, improved muscle lipid composition by reducing triglycerides (TG) and LDL-C contents while increasing beneficial phospholipids. Notably, the composite seaweed feeds, particularly FNKM2, showed more pronounced effects on growth and lipid-related parameters, with WGR reaching 1.66-fold, accompanied by a 1.33-fold increase in HDL-C and a 24.20% decrease in crude lipid content. In addition, the composite seaweed diets (FNKM1 and FNKM2) significantly downregulated most of the differentially abundant lipids in muscle. Among these, TG and phospholipids were significantly reduced in the FNKM1 group. These changes were accompanied by the upregulation of fatty acid oxidation genes (cpt1, ppara, pgc-1a) and the TG hydrolysis-related gene (lpl). Both feeds also enhanced immune-antioxidant capacity (∑IoI >1): FNKM1 significantly increased ACP, ALP, lysozyme, GSH-Px, and CAT activities, whereas FNKM2 increased ACP, ALP, and CAT activities. Both groups modulated hepatic cytokine expression, including il-4, il-1b, and tnf-a. Overall, the composite seaweed feeds contributed to improved growth, optimized lipid metabolism, and enhanced immune function in large yellow croaker, offering a scientific basis for functional feed development in intensive aquaculture.