Tea Saponin Exerts Dose-Dependent Dual Effects on Growth and Hepatic Health in Hybrid Grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂) Fed a High-Lipid, Low-Protein Diet via Redox-Immune Regulation
by
,
Shengrong Guo
1,
Jun Yu
1,2,
Lili Shi
3,
Beiping Tan
1,4,
Shuang Zhang
1,4,* and
Xiaobo Yan
1,2,* 1
Laboratory of Aquatic Nutrition and Feed, College of Fisheries, Guangdong Ocean University, Zhanjiang 524088, China
2
Ocean College, Fujian Polytechnic Normal University, Fuqing 350300, China
3
Department of Marine Biology, Shenzhen Institute of Guangdong Ocean University, Shenzhen 518116, China
4
Aquatic Animals Precision Nutrition and High Efficiency Feed Engineering Research Center of Guangdong Province, Zhanjiang 524088, China
*
Authors to whom correspondence should be addressed.
Animals 2026, 16(9), 1408; https://doi.org/10.3390/ani16091408
Submission received: 27 March 2026
/
Revised: 20 April 2026
/
Accepted: 1 May 2026
/
Published: 4 May 2026
(This article belongs to the Special Issue Genomics, Evolution, and Biodiversity of Fishes)
Simple Summary
High-lipid, low-protein feeds can help to reduce aquaculture costs and lower nitrogen waste, but they may also damage liver health and weaken disease resistance in hybrid grouper, a high-value marine fish widely farmed in Asia. In this study, we examined whether tea saponin, a natural compound from camellia seed meal, could help to protect these fish when they were fed this kind of diet. We found that adding 0.05–0.10% tea saponin improved growth, supported liver health, strengthened the body’s natural ability to fight oxidative cell damage, and reduced inflammatory cell infiltration and pro-inflammatory cytokine expression. However, too much tea saponin had the opposite effect, slowing growth and causing clear signs of liver injury. The best results were seen at a relatively low inclusion level, showing that careful dose control is essential. These findings suggest that tea saponin could be developed as a practical feed additive to improve fish health and production efficiency when high-lipid, low-protein feeds are used. This could help farmers to reduce feed costs and ensure more reliable production of this valuable marine fish.
Abstract
High-lipid, low-protein diets are economically advantageous in aquaculture costs but often induce hepatic damage, immunosuppression and metabolic disorders in carnivorous fish like hybrid grouper (Epinephelus fuscoguttatus ♀ × E. lanceolatus ♂). Tea saponin (TS) is a bioactive triterpenoid from camellia seed meal with excellent lipid-lowering and anti-inflammatory effects. The purpose of the current study was to investigate the dose-dependent impacts of TS supplementation at 0% (control, T0), 0.05% (T5), 0.10% (T10), 0.15% (T15), and 0.20% (T20) in diets formulated to contain 42% crude protein and 16% crude lipid on juvenile hybrid grouper (17.51 ± 0.03 g), with three replicate tanks per treatment, over a 4-week feeding trial. The results showed that low TS supplementation (0.05%) improved growth, with the effect limited to final average weight (FAW), whereas higher doses (≥0.15%) reduced weight gain. The T5 group exhibited the highest hepatic total antioxidant capacity and superoxide dismutase activity, consistent with the corresponding gene expression, and the lowest malondialdehyde and reactive oxygen species levels. Lysozyme activity and immunoglobulin M content were significantly higher in T5–T15 groups (p < 0.05). Furthermore, appropriate TS significantly upregulated anti-inflammatory cytokines (p < 0.05) and downregulated pro-inflammatory factors. Histologically, 0.10% TS reduced inflammatory infiltration, while high doses caused hepatocyte rupture and lipid vacuolation. Transcriptomic analysis further elucidated that the beneficial effects of low-dose TS were linked to the activation of PPAR signaling, fatty acid catabolism, and cellular quality control pathways, while high-dose TS triggered stress-related and biosynthetic programs. In conclusion, moderate TS supplementation (0.05–0.10%) ameliorated diet-induced oxidative stress and immunosuppression, improved growth performance and anti-inflammatory factor expression, whereas over-addition inhibited growth and exacerbated hepatic damage. Based on a quadratic model, the optimal dietary TS level for maximizing growth under this low-protein, high-lipid regimen is estimated at 0.055%.
