A comparative study of soybean meals for vannamei shrimp

The shrimp industry faces a constant challenge: reducing its dependence on fishmeal, a costly and limited resource. Soybean meal has established itself as the primary plant-based alternative, but are all soy products created equal? A recent scientific study published in the journal Aquaculture by researchers from Auburn University, Purdue University, Suez University, and the Escuela Superior Politécnica del Litoral (ESPOL) delves into this question, evaluating how different types of processed soybean meals affect the performance, gut health, and physiology of the Pacific white shrimp (Litopenaeus vannamei). The findings from this research are key to formulating more sustainable and efficient diets, demonstrating that the choice of soy type and its processing are critical to successful cultivation.

The challenge of vegetable proteins

The transition to diets with less fishmeal is an economic and environmental necessity. Solvent-extracted soybean meal (SE-SBM) is the most common plant-based ingredient in shrimp feeds. However, soy contains anti-nutritional factors (ANFs) such as oligosaccharides, trypsin inhibitors, and certain antigens that can limit its digestibility and negatively impact the animal’s performance.

To address this, the industry has developed more refined soy products through various technological processes and new genetic varieties. These products, though more expensive, promise a higher protein concentration and a lower load of ANFs, opening the door for greater inclusion levels in diets. But does their improved performance justify the cost?

Putting soy diets to the test

To answer this question, researchers conducted two eight-week trials with L. vannamei shrimp, replicating commercial farming conditions:

1. A “greenwater” system: An outdoor recirculating system that simulates the conditions of a pond with natural productivity.
2. An indoor biofloc system: An intensive culture system based on bacterial flocs that also provides supplemental nutrition.

The researchers formulated nine isonitrogenous and isolipidic diets (containing the same amount of protein and fat). The baseline diet contained 48% conventional soybean meal (SE-SBM). This was replaced, at 50% and 100% levels, by four types of processed soy:

• Low-oligosaccharide soybean meal (LO-SBM): Sourced from a soy variety developed to contain fewer indigestible carbohydrates.
• Soy protein concentrate (SPC): A highly refined product from which soluble carbohydrates have been removed.
• Enzyme-treated soybean meal (ET-SBM): Subjected to enzymatic treatment to break down complex proteins and ANFs.
• Expeller-pressed soybean meal (EP-SBM): Obtained through mechanical oil extraction, without the use of solvents.

Additionally, a reference diet based exclusively on animal proteins (fishmeal and poultry by-product meal) was included for comparison.

Growth results: Processed soy takes the lead

The growth results revealed significant differences among the diets, although survival was high and similar across all groups (over 92% in the greenwater system and 85% in the biofloc system).

In the greenwater system:

• Top-performing diets: Shrimp fed the basal diet (SE-SBM) and those with 50% and 100% replacement by low-oligosaccharide soybean meal (LO-SBM) showed the best final weights, even surpassing the animal protein diet.
• Lowest performance: The diet with a 100% replacement by soy protein concentrate (SPC) and the expeller-pressed soy diet (EP-SBM) resulted in lower growth.

In the indoor biofloc system:

• The clear winner: The diet with 100% replacement by LO-SBM produced the highest final weight, reaching 15.5 grams.
• Poorest performance: Again, the 100% SPC diet showed the lowest growth (11.78 g) and the worst feed conversion ratio (FCR of 2.11), indicating that the shrimp did not efficiently utilize this feed.
• Intermediate results: Diets with enzyme-treated soy (ET-SBM) and the animal protein diet performed well, similar to the basal diet.

These results suggest that soy products that reduce complex carbohydrates (like LO-SBM) or improve digestibility through treatments (like ET-SBM) are superior alternatives to animal protein in these culture systems.

Does soy affect the shrimp’s intestinal health?

A primary concern when using high levels of soy is the risk of inducing intestinal inflammation (enteritis). However, one of the most relevant findings of this study is that, after detailed histological analysis, no signs of damage or inflammation were found in the shrimp’s intestine in any of the tested diets. Neither the height of the intestinal folds nor the absorbent cells (enterocytes) showed significant differences, even with the highest soy inclusion levels.

Gene expression analysis reinforced this observation.

• In the greenwater trial, there were no significant changes in genes related to inflammation or immunity.
• In the biofloc system, shrimp fed SPC and conventional SBM showed a general downregulation of the analyzed genes. Interestingly, shrimp fed LO-SBM showed higher expression of the anti-inflammatory gene TGF-ß1 compared to those fed SPC, and those fed EP-SBM showed higher expression of the antioxidant gene SOD, which could indicate beneficial immune responses.

The absence of enteritis contradicts some previous studies and suggests that in systems with natural productivity (greenwater and biofloc), the potential negative effects of soy ANFs may be mitigated.

Conclusion: Not all soy is created equal

This study conclusively demonstrates that high-quality soy products can not only effectively replace animal protein in diets for L. vannamei but, in some cases, may even outperform it.

The key takeaways for producers and nutritionists are:

1. Low-oligosaccharide soybean meal (LO-SBM) is an excellent option: It consistently delivered superior growth performance, especially in biofloc systems.
2. Enzyme-treated soybean meal (ET-SBM) is a viable alternative: It offered good performance, positioning it as a solid choice.
3. Caution with Soy Protein Concentrate (SPC): At very high inclusion levels (fully replacing conventional SBM), it negatively affected growth and feed efficiency.
4. Intestinal health is not compromised: In realistic culture systems like greenwater and biofloc, high inclusions of processed soy did not cause observable intestinal damage.

This research validates the use of improved soybean meals to advance toward a more sustainable and profitable shrimp aquaculture, highlighting that innovation in ingredient processing is fundamental to the future of aquafeed nutrition.

Contact
Khanh Q. Nguyen
School of Fisheries, Aquaculture, and Aquatic Sciences, Swingle Hall, Rm 203, Auburn University
Auburn, AL 36849, USA.
Email: khanhnguyen@auburn.edu

Reference
Nguyen, K. Q., Hussain, A. S., Araujo, A. N., Strebel, L. M., Corby, T. L., Rhodes, M. A., Bruce, T. J., Cuéllar-Anjel, J., & Davis, D. A. (2026). Effects of different soybean protein sources on growth performance, feed utilization efficiency, intestinal histology, and physiological gene expression of Pacific white shrimp (Litopenaeus vannamei) in green water and indoor biofloc system. Aquaculture, 611, 743021. https://doi.org/10.1016/j.aquaculture.2025.743021

Milthon Lujan

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.