Pre-Digested Feeds: A New Trend in Aquaculture Nutrition

Formulated feed is a critical component of aquaculture production, ing for 50% to 70% of total production costs. The reliance on expensive and potentially unsustainable ingredients like fishmeal presents a major challenge. As a result, the search for alternative ingredients has intensified.

Fermented ingredients have emerged as a promising option, offering a balanced nutritional profile at a lower cost. A team of scientists from Ningbo University and Fujian Agriculture and Forestry University published a scientific review in Aquaculture Reports, providing a comprehensive overview of recent advances in the use of fermented feed ingredients in aquaculture.

What are fermented or Pre-digested ingredients?

Fermentation, a technique used for centuries in food preparation and preservation, has gained significant attention in animal nutrition. Fermenting feed improves nutrient accessibility by converting complex carbohydrates, proteins, and other macromolecules into bioavailable compounds through microbial activity.

The fermentation process enhances digestibility, leading to better nutrient absorption and utilization, promoting animal growth, nutritional immunity, and overall health.

Fermented feeds, also known as pre-digested feeds, are characterized by high levels of enzymes, probiotics, and organic acids that contribute to improved digestion. These components are particularly effective in neutralizing anti-nutritional factors such as phytates and tannins, which can impair nutrient absorption and immune responses.

Types of fermentation processes

There are two main types of fermentation:

• Solid-State Fermentation (SSF): This method involves fermenting feed materials using beneficial microorganisms in the absence of free water or with minimal moisture. It offers benefits such as enhanced nutritional value and cost-effectiveness.
• Liquid-State Fermentation (LSF): This method uses a liquid substrate as the fermentation medium. It provides advantages like balanced nutrient concentrations, consistent fermentation, and good palatability.

Factors affecting the quality of fermented ingredients

According to the review, several factors influence the quality of fermented ingredients, including the fermentation substrates, microorganisms, temperature, and duration. Environmental conditions, such as the initial pH of the fermentation medium, are also critical. To enhance quality, it is essential to ensure an effective combination of substrates, microbial strains, and environmental parameters.

Sources of Fermented Protein

Choosing which protein to ferment is key. While fishmeal has long been dominant, its sustainability is in question. Thus, science is exploring alternatives:

• Fermented Plant Proteins: Soybean meal, wheat gluten, and other plant sources are abundant and cost-effective. However, plant proteins contain various anti-nutritional factors (ANFs) and fibers that significantly affect feed palatability and nutrient digestion. Fortunately, fermentation can improve both the quality and nutritional value of plant proteins for aquaculture use.
• Fermented Animal Proteins: By-products such as poultry meal or fish processing waste have excellent amino acid profiles and are well accepted by aquatic species. Fermentation can further enhance their digestibility.
• Single-Cell Proteins (S): Cultivated yeasts, bacteria, or microalgae can transform low-cost nutrients — even waste — into high-quality proteins. They are highly efficient and represent a compelling option for circular economy strategies in aquaculture.

Benefits of using fermented ingredients

The adoption of fermented ingredients as alternatives to fishmeal has successfully eased fishmeal shortages while reducing dependency on wild fish stocks — a critical step toward environmental sustainability in aquaculture. Additionally, fermented feeds enhance profitability for small-scale farmers by lowering feed costs and improving consumer safety through reduced antibiotic use.

Improved feed intake and growth performance

Fermented ingredients are cost-effective, abundant, and have species-specific replacement potential. Empirical studies suggest that partial replacement of fishmeal (20%–50%) with fermented ingredients reduces feed costs without compromising growth performance.

Regulation of intestinal epithelial development

Fermented ingredients, rich in probiotics and their metabolites, directly influence the development of the intestinal epithelium. Intestinal histology is a crucial indicator of healthy gut development, which is directly linked to overall animal health and survival.

Modulation of gut immune response

Fermented ingredients serve as functional carriers of immunomodulatory microorganisms, synergistically enhancing digestive efficiency and immune homeostasis in aquatic species.

Strengthening the gut microbial barrier

The intestinal barrier is the first line of defense against pathogenic invasion. Fermented ingredients boost this protective function by dose-dependently modulating mucosal immunity and reshaping the microbiota.

Enhancing environmental and water quality

Fermented feeds improve water quality by enhancing feed stability and reducing waste. Water stability is a critical factor in overall feed quality.

Challenges and opportunities of pre-digested feeds

Despite the many advantages outlined in the study, challenges remain. One major hurdle is the lack of standardized manufacturing technology for fermented ingredients, leading to variations in product quality. This inconsistency creates mistrust and complicates informed decision-making for producers.

To unlock the full potential of fermented ingredients, the following are needed:

• Clear quality standards: Define what constitutes a high-quality fermented ingredient.
• Ongoing research: Better understand how different microbial strains interact with various raw materials.
• Smart strain selection: Not all bacteria or yeasts work equally — strains must be selected based on the ingredient and intended use.
• Training and outreach: Educating professionals and farmers on the benefits and proper handling of these ingredients is essential.

Conclusion: A fermented and promising future

As the scientific review highlights, fermented ingredients — especially those derived from plant protein sources — offer significant potential for cost-effective and sustainable aquafeeds. While much of the research has focused on protein source selection, the review notes that “uncertainties remain regarding the interaction between the same microbial strain and different raw materials, as well as the fermentation characteristics of mixed strains.”

This article presents a comprehensive overview of recent advances in using fermented feed ingredients in aquaculture. The adoption of pre-digested feeds holds great promise for enhancing the sustainability and profitability of the aquaculture industry, while meeting the growing global demand for aquatic products.

The study was funded by the Key Project of the Natural Science Foundation of Zhejiang Province, the National Natural Science Foundation of China, the Pingyang County Science and Technology Strengthening Agriculture Industry Upgrading Project, the Key Scientific and Technological Grant of Zhejiang for Breeding New Agricultural Varieties, the Science and Technology Innovation Yongjiang 2035 Key R&D Project of Ningbo, and the Ningbo University Marine College t Key Laboratory Open Fund Project.

Yang Du
Laboratory of Biochemistry and Molecular Biology, School of Marine Sciences, Ningbo University
Ningbo 315211, China.
Email: [email protected], [email protected]

Jiong Chen
Email: [email protected], [email protected]

Refence (open access)
Li, B., Boukhennou, A., Shao, J., Miao, L., Du, Y., & Chen, J. (2025). Application status and development prospect of fermented ingredients in aquaculture. Aquaculture Reports, 42, 102842. https://doi.org/10.1016/j.aqrep.2025.102842