Effects of Dietary Steroid Saponins on Growth Performance, Serum and Liver Glucose, Lipid Metabolism and Immune Molecules of Hybrid Groupers (♀<i>Epinephelus fuscoguttatus</i> × ♂<i>Epinephelus lanceolatu</i>) Fed High-Lipid Diets

Abstract

High-lipid diets are attributed to excessive lipid deposition and metabolic disturbances in fish. The aim of this experiment was to investigate the effects of steroidal saponins on growth performance, immune molecules and metabolism of glucose and lipids in hybrid groupers (initial weight 22.71 ± 0.12 g) fed high-lipid diets. steroidal saponins (0%, 0.1% and 0.2%) were added to the basal diet (crude lipid, 14%) to produce three experimental diets, designated S0, S0.1 and S0.2, respectively. After an 8-week feeding trial, no significant differences were found between the S0 and S0.1 groups in percent weight gain, specific growth rate, feed conversion ratio, protein efficiency ratio and protein deposition rate (p > 0.05). All those in the S0.2 group were significantly decreased (p 0 group, fish in the S0.1 group had lower contents of serum triglyceride and low-density lipoprotein cholesterol and higher high-density lipoprotein cholesterol and glucose (p 0.1 group than in the S0 group (p 0.1 group than in the S0 group (p 0.1 group than in the S0 group. Interleukin-10 mRNA expression in the S0.1 group was significantly higher than that in the S0 group, while the expression of interleukin-6 and tumor necrosis factor-α genes were significantly lower than those in the S0 group. In summary, adding 0.1% steroidal saponins to a high-lipid diet not only promoted lipolysis in fish livers, but also activated glycolysis pathways, thus enhancing the utilization of the dietary energy of the groupers, as well as supporting the fish’s nonspecial immune-defense mechanism.

Keywords

• steroidal saponins
• hybrid grouper
• high-lipid diet
• glucose and lipid metabolism
• nonspecial immune