Fiber in shrimp diets: What is the optimal level for Penaeus vannamei?

In modern aquaculture, the search for sustainable and cost-effective ingredients to replace fishmeal is a priority. Plant-based ingredients like soybean meal are popular alternatives, but their inclusion inevitably increases crude fiber levels in shrimp feed. Unlike terrestrial animals, penaeid shrimp lack the necessary enzymes, such as cellulase, to efficiently digest fiber.

Although an adequate level of fiber is crucial for intestinal health and digestion, an excess can be counterproductive. This raises a fundamental question for nutritionists and producers: What is the fiber tolerance limit for the Pacific white shrimp (Penaeus vannamei)? A recent study by researchers from the ICAR-Central Institute of Fisheries Education and the ICAR-Central Institute of Brackishwater Aquaculture aimed to answer this question by evaluating the effects of different crude fiber levels on the growth, physiology, and gut microbiota of this important aquaculture species.

Key conclusions

• Optimal Growth Level: Pacific white shrimp (Penaeus vannamei) can tolerate and maintain healthy growth with dietary crude fiber levels up to 5.20%.
• Negative Impact on Performance: Diets with fiber levels exceeding 5.20% (specifically 7.62%, 10.20%, and 12.56%) significantly reduce weight gain and worsen the feed conversion ratio (FCR).
• Tissue Damage: Excessive amounts of fiber cause severe structural damage to the hepatopancreas and intestine, including edema, cellular hypertrophy, and epithelial degeneration.
• Microbiota Modulation: A fiber level of 5.20% promotes a beneficial microbial balance in the gut, increasing the abundance of bacteria like Meridianimaribacter, which is associated with fiber degradation, and reducing potential pathogens.

Study methodology: Testing the limits of fiber

To determine fiber tolerance, the researchers conducted a 45-day feeding trial. Five isonitrogenous and isolipidic diets (containing the same amount of protein and fat) were formulated, with the only variable being the percentage of crude fiber, using cellulose as the source.

The tested fiber levels were:

• 2.58% (Control)
• 5.20%
• 7.62%
• 10.20%
• 12.56%

Juvenile shrimp with an initial average weight of 4.01 g were distributed into experimental tanks and fed three times a day. At the end of the study, growth parameters, feed efficiency, hepatopancreas and intestinal health, and the composition of the gut microbiota were evaluated.

Impact on growth and feed efficiency: The breaking point at 5.20%

The study’s results were clear: shrimp growth performance is directly linked to the dietary fiber level.

• Optimal growth: Shrimp fed diets with 2.58% and 5.20% fiber showed the best results in terms of weight gain, percent weight gain, and specific growth rate, with no significant differences between the two groups.
• Performance decline: Starting at the 7.62% fiber level, growth began to decrease significantly. The poorest performance was recorded in the group with the highest fiber level (12.56%).
• Feed efficiency: The Feed Conversion Ratio (FCR) was lowest (best) in the 2.58% and 5.20% groups. As fiber content increased, the FCR worsened, indicating that the shrimp utilized the feed less effectively.

These findings suggest that a fiber level up to 5.20% is safe and does not compromise growth, but exceeding this threshold has direct negative consequences on productivity.

Effects on digestion and oxidative stress

Excess fiber not only affects growth but also the shrimp’s ability to digest nutrients and maintain physiological balance.

• Digestive enzyme activity: The activity of key digestive enzymes in the hepatopancreas—such as trypsin and chymotrypsin (for proteins), amylase (for carbohydrates), and lipase (for lipids)—was significantly reduced in shrimp that consumed diets with more than 5.20% fiber. This decrease suggests that high fiber concentrations interfere with the digestive process, limiting the absorption of essential nutrients.
• Antioxidant response: High fiber levels also generated oxidative stress. The activity of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) was higher in the 2.58% and 5.20% fiber groups. In the higher-fiber groups, the activity of these protective enzymes decreased, indicating an imbalance and potential cellular damage that contributed to the overall poor performance.

Visible damage to the hepatopancreas and intestine

Histological (microscopic) analysis of the tissues revealed the physical damage caused by excess fiber.

• Hepatopancreas: While shrimp in the 2.58% and 5.20% groups showed a healthy and well-organized tissue structure, those in the high-fiber groups exhibited severe alterations. An increase in intertubular space (edema), deformed tubules, and hypertrophied cells were observed, which are clear signs of severe tissue damage in the 12.56% group.
• Intestine: Similarly, the intestine of shrimp in the control and 5.20% groups had a healthy epithelial structure. However, as fiber increased, epithelial degeneration, inflammation, excessive mucus secretion, and the complete loss of the peritrophic membrane were observed in the 12.56% group. This damage severely compromises the intestine’s ability to absorb nutrients and act as a protective barrier.

Fiber and the gut microbiota: A delicate balance

Diet is a key modulator of the intestinal microbial community. In this study, although overall diversity did not vary significantly, the composition did.

The most interesting finding was in the 5.20% fiber group. In this treatment, the relative abundance of the genus Meridianimaribacter increased substantially. This bacterial genus is known for its ability to degrade lignocellulose, suggesting it may play a beneficial role in helping the shrimp manage moderate fiber levels.

Furthermore, in the 5.20% and 7.62% groups, a reduction in the abundance of potentially pathogenic genera such as Vibrio, Acinetobacter, and Stenotrophomonas was observed compared to the control group. This indicates that a moderate level of fiber may help maintain a healthier gut microbiome.

Conclusion: 5.20% as a safe and beneficial limit

This study conclusively demonstrates that crude fiber in the diet of Penaeus vannamei is a double-edged sword. A level up to 5.20% can be safely included in feeds, maintaining optimal growth, healthy digestive function, and promoting a beneficial gut microbiota.

However, exceeding this threshold is detrimental. Crude fiber levels of 7.62% or higher lead to reduced growth, lower feed efficiency, increased oxidative stress, and significant structural damage to vital digestive organs.

These findings offer practical and valuable guidance for feed formulators, enabling them to optimize the use of plant-based ingredients and maximize shrimp health and performance, thereby contributing to more sustainable and efficient aquaculture practices.

Contact
J. Syama Dayal
Nutrition, Genetics & Biotechnology Division, ICAR- Central Institute of Brackishwater Aquaculture
Chennai 600028, India
Email: syamadayal@gmail.com

Reference (open access)
Gokulnath, S., Syama Dayal, J., Varghese, T., Ananda Raja, R., Sivaramakrishnan, T., Ambasankar, K., Deo, A. D., Ranjith, N., Suganya, N., Kumaravel, J., & Ashok Kumar, J. (2026). Effects of varying levels of dietary crude fibre on growth, physio-biochemical responses, and gut microbiota in Pacific white shrimp, Penaeus vannamei. Aquaculture, 612, 743157. https://doi.org/10.1016/j.aquaculture.2025.743157

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.