Why Digestibility Matters in Modern Shrimp Feed

By Dr. Wiphada Mitbumrung, Ph.D. Applied Marine Biosciences — Wed Jun 10 2026

In modern shrimp farming, feed formulation has changed significantly. Due to the high cost and limited availability of fishmeal, many commercial shrimp feeds now include higher levels of soybean meal and other plant-based ingredients. This change helps reduce feed cost and supports more sustainable feed production. However, replacing animal protein with plant protein is not always simple because shrimp are not naturally herbivorous animals.

Shrimp may consume a variety of natural food items in the pond, including plankton, detritus, small organisms, and organic particles. However, their digestive system is not designed to digest plant protein as efficiently as true herbivorous animals. This is why feed digestibility has become one of the most important factors in shrimp nutrition today.

Shrimp Are Carnivorous Omnivores

Zooplankton / Phytoplankton, Diatoms, Microalgae / Detritus, Microbial flocs / Organic particles / Small benthic organisms

Litopenaeus vannamei: More Omnivorous, but Not Herbivorous

Litopenaeus vannamei, or Pacific white shrimp, is generally considered an omnivorous shrimp species. In pond culture, L. vannamei can utilize a wide range of food sources, including formulated feed, plankton, detritus, microbial flocs, and organic particles. This flexibility is one reason why vannamei can perform well in intensive and semi-intensive farming systems.

However, being omnivorous does not mean that vannamei is naturally herbivorous. Its digestive system can accept some plant-based ingredients, but it is still limited in its ability to completely digest complex plant proteins and carbohydrates, especially when high levels of soybean meal or other plant meals are used in the feed. Therefore, when feed formulation contains more plant protein, digestibility support becomes important to help shrimp absorb nutrients more efficiently.

Polychaete benthic worms / Small benthic crustaceans / Small bivalve / mollusk tissue / Organic animal detritus, benthic animal matter

Penaeus monodon: Stronger Carnivorous Tendency

Penaeus monodon, or black tiger shrimp, has a stronger carnivorous feeding tendency compared with L. vannamei. In nature, P. monodon feeds more on animal-based food sources such as small benthic organisms, mollusks, worms, crustaceans, and organic animal matter. Because of this, its digestive system is generally more suited to animal protein sources.

When high levels of plant protein are used in P. monodon feed, digestibility challenges may become more obvious. Poorly digested plant ingredients can reduce protein utilization, increase gut residue, and place more stress on the hepatopancreas and digestive system. This can affect growth, FCR, gut health, and disease resistance.

The Challenge of Plant Protein in Shrimp Feed

Plant-based ingredients are useful in feed formulation, but they also come with nutritional limitations. Soybean meal and other plant proteins may contain anti-nutritional factors that interfere with digestion and nutrient absorption. These compounds can reduce protein utilization, irritate the gut, and increase the amount of undigested material passing through the digestive tract. When plant protein is not fully digested, shrimp cannot efficiently convert feed into body mass. This means part of the feed protein is wasted instead of being used for growth. As a result, farmers may observe higher feed consumption, slower growth, and poorer feed conversion ratio.

1. Poor Digestibility Increases Gut and Hepatopancreas Stress

When shrimp cannot digest feed completely, more undigested feed remains in the gut. This increases the workload of the digestive system, especially the hepatopancreas, which plays a major role in enzyme production, digestion, nutrient absorption, and energy metabolism. A high level of undigested feed residue may disturb gut balance and create a favorable environment for harmful bacteria. In pond culture, this condition can increase the risk of gut inflammation, white feces, weak digestion, and Vibrio-related problems. Therefore, poor digestibility is not only a nutrition issue; it can also become a health issue.

**2. Undigested Feed Can Support Vibrio Proliferation**

The shrimp gut is an important site for microbial activity. When feed is well digested, nutrients are absorbed efficiently and less residue remains available for opportunistic bacteria. However, when plant-based feed ingredients are poorly digested, more organic residue remains in the gut. This residue can support the growth of opportunistic bacteria, including Vibrio. Under stressful culture conditions, such as high temperature, poor water quality, or unstable pond conditions, Vibrio can multiply faster and cause digestive problems. Once the gut environment becomes unstable, shrimp may show reduced feeding, loose feces, white feces, poor growth, and increased disease susceptibility.

3. High FCR Means Feed Is Not Being Used Efficiently

One of the most visible effects of poor digestibility is high FCR. Farmers may feed more, but shrimp do not grow proportionally. This means the shrimp are eating feed, but not converting it efficiently into biomass. A high FCR increases production cost because feed is the largest operating cost in shrimp farming. It also increases organic waste in the pond because undigested nutrients are released through feces or remain as uneaten feed. This can further reduce water quality, increase bacterial pressure, and create a cycle of poor digestion, poor pond condition, and poor shrimp performance.

Why Enzyme Supplementation Is Becoming More Important

In the past, shrimp feeds relied more heavily on fishmeal and other animal protein sources. These ingredients were highly digestible and well matched to the natural digestive capacity of shrimp. However, today’s feed formulas are different. With more soybean meal and plant-based protein, farmers must consider not only the nutrient percentage written on the feed label, but also how much of that nutrient shrimp can actually digest and absorb. A feed may contain high crude protein, but if shrimp cannot digest that protein efficiently, the real nutritional value becomes lower. Therefore, digestibility is as important as protein level. The key question is no longer only, “How much protein is in the feed?” but also, “How much of this protein can shrimp truly use?”

In modern shrimp feed containing more plant-based ingredients, enzyme supplementation is becoming increasingly important. The right enzyme blend can help break down complex protein and carbohydrate structures in plant ingredients into smaller and more digestible molecules. For example, protease helps break down protein into smaller peptides and amino acids. Carbohydrase enzymes help break down complex carbohydrates and fiber-like structures in plant materials. When these nutrients are broken down more effectively, shrimp can absorb them more easily and use them for growth.

Benefits of Better Digestibility

Improving digestibility does not only mean that shrimp can digest feed better. It also means shrimp can use nutrients more efficiently for growth, gut health, and overall performance. When feed digestibility improves, shrimp can absorb more amino acids for muscle development. Less undigested feed remains in the gut, which helps maintain a cleaner and healthier intestinal environment. The hepatopancreas also faces less digestive burden, allowing shrimp to maintain better metabolic balance.

Better digestibility may lead to several practical benefits:

Shrimp can utilize protein more efficiently for growth.
Gut cleanliness and gut stability improve.
The risk of digestive stress, white feces, and Vibrio pressure may be reduced.
Feed efficiency improves, helping farmers reduce unnecessary feed waste.
Overall pond organic load may also decrease because less nutrient waste is released into the culture system.

Take Home Message: White Feces Is Not Always Only an EHP or Vibrio Problem

White feces is often blamed only on EHP or Vibrio, but the root cause can also start from poor feed digestibility. When shrimp cannot fully digest the feed, especially feed with high plant protein, more residue remains in the gut. This residue irritates the intestine, increases stress on the hepatopancreas, and creates a good condition for Vibrio to grow. Therefore, white feces should not be treated only as a pathogen problem. Farmers also need to check feed quality, digestibility, overfeeding, and gut condition. If the shrimp cannot properly digest and utilize the feed, the gut becomes weak and pathogens can take advantage more easily.