The search for sustainable and cost-effective alternatives to fishmeal is a cornerstone of modern aquaculture. A recent study, published by researchers from Ningbo University, the Collaborative Innovation Center for Zhejiang Marine High-efficiency and Healthy Aquaculture, and Zhejiang Fengyu Marine Organism Products Co., Ltd., evaluated the potential of enzymatically hydrolyzed marine proteins (EMP) as a functional supplement in low-fishmeal diets for the Pacific white shrimp (Litopenaeus vannamei). The results extend far beyond simple ingredient replacement.
Key conclusions
- It is possible to reduce the fishmeal content in the diet by up to 4% (by replacing it with 2% EMP) without negatively affecting the shrimp’s growth performance.
- Supplementation with 1% EMP activated genes related to neurotransmitters in the cerebral ganglion, suggesting an improvement in appetite and feed intake.
- EMP promoted lipid breakdown, reducing total cholesterol, triglycerides, and fat deposition in the hepatopancreas.
- A 1% dose of EMP improved intestinal structure by increasing the height and width of villi, which promotes better nutrient absorption.
The fishmeal challenge and the marine byproduct solution
Fishmeal (FM) is a high-quality nutritional ingredient, but its limited supply and high cost pose a constant challenge to the shrimp industry. In this context, the valorization of byproducts from aquatic processing—such as fish heads, squid viscera, and crustacean shells—emerges as a sustainable strategy.
These byproducts, rich in proteins and bioactive compounds, can be transformed through enzymatic hydrolysis into Hydrolyzed Marine Proteins (EMP). This controlled process breaks down proteins into smaller peptides and free amino acids, enhancing their digestibility and functionality. The EMP used in this study is a complex that includes fish peptides, enzymatically digested squid viscera, and seaweed polysaccharides.
How was the effect of EMP evaluated in shrimp?
To determine its efficacy, an 8-week feeding trial was conducted with juvenile Litopenaeus vannamei (initial weight of 2.51 g). Three diets were formulated:
- Control Diet: 30% fishmeal.
- 1% EMP Diet: 28% fishmeal, supplemented with 1% EMP.
- 2% EMP Diet: 26% fishmeal, supplemented with 2% EMP.
During the trial, parameters such as growth performance, body composition, intestinal health, and metabolic indicators were measured at the genetic and biochemical levels.
Key findings: More than just a substitute
Equivalent growth performance
One of the most critical outcomes for producers is that there were no significant differences in growth performance (final weight, weight gain, specific growth rate, and feed efficiency) between shrimp fed the experimental diets and the control diet. This demonstrates that EMP can effectively replace up to 4% of fishmeal without compromising productivity.
A potent appetite stimulant
How is growth maintained with less fishmeal? The answer appears to lie in appetite. Shrimp fed the 1% EMP diet showed significant upregulation of genes related to neurotransmitters and appetite in the cerebral ganglion (oa-ta, tdc, tbh, and ghs-r1).
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These genes are involved in the synthesis of octopamine and tyramine, neurotransmitters that regulate food intake in invertebrates. In essence, EMP sent signals to the shrimp’s brain to stimulate feeding, thereby compensating for the reduction in fishmeal, a known attractant.
Optimization of lipid and protein metabolism
EMP supplementation influenced not only feeding behavior but also how the shrimp process nutrients.
- Lipid Metabolism: Shrimp in the control group had higher levels of total cholesterol, triglycerides, and low-density lipoprotein cholesterol (LDL-C) in their hemolymph. Conversely, the EMP groups showed higher expression of genes associated with lipid breakdown (lipolysis), such as atgl and hsl, and with fatty acid beta-oxidation. Histologically, this resulted in less lipid droplet accumulation in the hepatopancreas of the 1% EMP group.
- Protein Synthesis: The 1% EMP diet significantly activated the mTORC1 signaling pathway in the hepatopancreas through the overexpression of genes like tor, rheb, and slc3a2. This pathway is a central regulator of cell growth and protein synthesis. As a result, shrimp in this group showed considerably higher body protein content compared to the control group.
Improvements in intestinal and hepatopancreas health
A healthy gut is fundamental to good nutrition. Histological analyses revealed that shrimp fed 1% EMP had an improved intestinal structure, with taller and wider folds. This increases the surface area for nutrient digestion and absorption.
Furthermore, the activity of key digestive enzymes like lipase and trypsin in the hepatopancreas was significantly higher in the EMP groups, indicating a greater capacity to break down fats and proteins. Notably, the 1% EMP dose proved to be the most beneficial for the overall health of the hepatopancreas.
Conclusion: Practical implications for the shrimp industry
This study demonstrates that hydrolyzed marine proteins (EMP) are a promising functional ingredient for shrimp feed formulation. Supplementation with 1% EMP not only allows for a 2% reduction in fishmeal inclusion without affecting growth but also provides additional benefits:
- It improves palatability and stimulates appetite through neural signaling.
- It promotes more efficient lipid metabolism, reducing fat accumulation.
- It activates protein synthesis pathways, leading to greater body protein deposition.
- It strengthens intestinal health, improving nutrient absorption capacity.
These findings suggest that EMP is a viable and sustainable strategy to reduce dependence on fishmeal while optimizing the metabolic health and performance of Litopenaeus vannamei. The 1% supplementation level appears to be an optimal ratio that balances nutritional efficacy and economic viability.
Contact
Qicun Zhou
Laboratory of Fish and Shellfish Nutrition, School of Marine Sciences, Ningbo University
Ningbo 315211, China.
Email: zhouqicun@nbu.edu.cn
Reference (open access)
Li, X., Xu, T., He, Y., Jin, M., Zhang, Y., Tang, F., & Zhou, Q. (2025). Dietary enzyme-hydrolyzed marine proteins supplementation promotes appetite, enhances lipid and protein metabolism in Litopenaeus vannamei fed reduced fish meal diets. Aquaculture Reports, 44, 103026. https://doi.org/10.1016/j.aqrep.2025.103026
Editor at the digital magazine AquaHoy. He holds a degree in Aquaculture Biology from the National University of Santa (UNS) and a Master’s degree in Science and Innovation Management from the Polytechnic University of Valencia, with postgraduate diplomas in Business Innovation and Innovation Management. He possesses extensive experience in the aquaculture and fisheries sector, having led the Fisheries Innovation Unit of the National Program for Innovation in Fisheries and Aquaculture (PNIPA). He has served as a senior consultant in technology watch, an innovation project formulator and advisor, and a lecturer at UNS. He is a member of the Peruvian College of Biologists and was recognized by the World Aquaculture Society (WAS) in 2016 for his contribution to aquaculture.
