Pellet Mill vs. Extrusion in Fish Feed Production: What Should You Choose?

In modern aquaculture, formulated feeds play a critical role in ensuring fish health, optimal growth, and feed efficiency. These feeds, produced primarily using either pellet mills or extrusion systems, are designed to meet the nutritional needs of various species while also supporting efficient farming operations.

Choosing the right feed production method is more than a technical decision—it's an economic one. Each method has distinct advantages depending on the desired feed characteristics, species requirements, processing capabilities, and cost structure.

Understanding Feed Types and Buoyancy Needs

One of the most important considerations in aquafeed manufacturing is buoyancy. Fish species differ in how they consume feed:

• Floating feeds are ideal for species like tilapia, carp, and catfish.

• Slow-sinking feeds are commonly used for trout, salmon, and yellowtail.

• Sinking feeds are necessary for species such as cod, shrimp, and river crab.

Feed buoyancy is influenced by both the formulation and the processing method, making the selection of equipment crucial for meeting these specific feeding behaviors.

Pellet Milling: Reliable for Sinking Feeds

Pellet mills use mechanical compression to form dense, sinking pellets. The process involves moderate moisture and temperature, producing feeds that are robust but generally limited in buoyancy control.

Pelleting is a simpler and more economical approach for feed mills that primarily produce sinking diets—particularly for shrimp and certain cold-water fish species. However, because the starch is not fully gelatinized in this method, nutrient digestibility may be lower, and feed integrity can suffer due to higher fines or dust.

Key Advantages of Pellet Mills:

• Lower equipment investment

• Suitable for high-density sinking feeds

• Less aggressive on heat-sensitive nutrients

  
  

Limitations:

• Cannot produce floating feeds

• Higher starch levels required for binding

• Lower feed digestibility and pellet durability

  
  

Extrusion: Versatility and Enhanced Feed Quality

Extrusion offers greater flexibility in aquafeed production. By controlling temperature, moisture, screw configuration, and processing time, extruders can produce floating, slow-sinking, or sinking feeds—all from a single system.

The key advantage of extrusion is the ability to gelatinize starch fully, which improves pellet integrity, floating properties, and nutrient availability. This “cooking” process increases feed digestibility and allows the inclusion of more varied and cost-effective ingredients, including lower levels of starch and higher-quality proteins.

Key Advantages of Extrusion:

• Produces both floating and sinking feeds

• Improved digestibility and nutrient availability

• Better pellet integrity and water stability

• Lower Feed Conversion Ratios (FCR)

  
  

Considerations:

• Higher equipment and operating costs

• Greater vitamin loss if not managed properly

• Requires tighter process control and skilled operation

  
  

Nutrient Retention and Feed Quality

While extrusion improves feed performance, the higher temperature and pressure involved can negatively impact certain vitamins*—particularly fat-soluble ones like A and D, and water-soluble B vitamins like thiamine and B6. This requires the use of stabilized vitamin forms and careful control of processing parameters.

*Although extrusion involves higher temperatures and pressures that can degrade sensitive vitamins, modern feed formulation strategies incorporate stabilized vitamin forms and precise process controls to mitigate these losses. These advances enable producers to maintain nutritional quality while benefiting from extrusion's feed performance advantages.

In contrast, the milder temperatures in pellet mills may help retain more sensitive nutrients, although nutrient digestibility may be compromised due to incomplete cooking.

Ultimately, both methods require robust formulation strategies and quality raw materials to ensure final feed quality, from floatability and size uniformity to nutritional consistency and shelf life.

Regardless of the manufacturing method used, the quality of raw materials, the expertise in feed formulation, and rigorous quality control procedures are critical to producing consistent, nutritionally balanced feeds. These factors ultimately determine the success of feed performance and fish health outcomes.

Economic Considerations

Extruded feeds typically come with higher upfront equipment and operating costs. However, these are often offset by:

• Improved feed conversion ratios

• Reduced formulation costs due to ingredient flexibility

• Less feed waste due to stronger pellet integrity

Pellet mills, on the other hand, offer lower capital investment and operating costs but may lead to higher FCRs and greater feed loss due to fines, particularly in less controlled environments.

Final Thoughts: Selecting the Right Process

There is no one-size-fits-all approach in aquafeed manufacturing. The ideal process depends on your production goals, target species, nutritional strategies, and budget. Here’s a quick guide:

Criteria	Pellet Mill	Extrusion
Feed Type	Sinking only	Sinking, slow-sinking, floating
Species	Shrimp, trout	Tilapia, catfish, salmon
Investment Level	Lower	Higher
Pellet Integrity	Moderate	High
Nutrient Digestibility	Moderate	High
FCR	Higher	Lower
Flexibility in Formulation	Limited	High

It is also important to recognize that feed manufacturing technologies continue to evolve, with innovations such as advanced extrusion techniques, alternative ingredient utilization, and precision nutrition shaping the future of aquafeed production. Staying informed about these developments allows producers to optimize feed quality and sustainability over time.

At Progressus Aqua Feed Milling Management Course, we help feed millers and aquaculture professionals gain deeper technical understanding and practical insights into feed production technologies through our training programs. Whether you're investing in new equipment or optimizing existing operations, knowing the right process for your target species and production goals is essential for long-term success.