Feed Quality & Nutritional Benefits Utilizing

Feed Quality & Nutritional Benefits Utilizing






Wenger Mediterranean Regional Division Manager.


There are a number of identified objectives when producing commercial aquatic feeds these being.

1) Target the nutritional requirements of the species to be fed

2) Meet the customer’s expectations with regards to quality.

3) Provide Environmental compliance.

4) Have favourable economic conditions.

With an every increasing and dramatic growth in capacity requirements for Aquaculture feeds the industry requires and are demanding sustainable practices regards Feed Quality.

1) Control over Feed buoyancy float / sink.

2) Renewable Ingredients.

3) Hygienic Feeds.

4) Improved Pellet durability, Water stability and digestibility to avoid pollution and the potential spread of disease.

Has with any commercial and industrial farming growth, feeding method and practices have developed and improved to meet the ever higher standards demanded by the farmer to gain economic returns and meet the ever increasing environmental requirements.

Aqua feeds being no different the first feeding methods were simple using trash feeds, hand fed in ponds then moving to pelletising of feeds and finally to the industry standard of using Extrusion Technology. Why did the industry move in this direction?

Hand feeding trash fish provided no consistency in the diet; storage was difficult, large risk of disease transmission and huge environmental challenges regards pollution.


The next stage pelletisation was a positive step forward providing

1) Increased Density and consistency

2) Improved storage.

3) Less Feed Waste.

4) Some improvement in reducing Water pollution.

Pelletising was economically feasible as it did provide high capacities; low processing cost and was a non-complex operation.

Unfortunately the disadvantages became all too apparent.

1) No control of buoyancy.

2) Low water stability.

3) Little flexibility to utilise available raw materials.

4) Diets based on process technology not full nutritional benefits.

5) Only low oil diets possible.

6) Starch gelatinization and digestibility limited.

7) Process not adequate for destruction of anti nutritional factors and pathogenic organisms.

Hence back in the early eighties Aquaculturasits looked towards the extrusion process as a potential flexible system to overcome the deficiencies of pelletisation.

The need to formulate diets on nutritional benefits and lower cost raw materials became the aim and goal to take the Aquaculture industry into an economical and commercial success.

Extrusion Technology offered the following advantages.

1) Complete control of floating and sinking feeds.

2) Importantly pasteurisation of feeds.

3) High level of starch gelatinization for improved water stability, durability and in some cases digestibility.

4) Raw Material Flexibility.

Raw materials constitute 70-80% of the cost of production of Aqua Feeds and more than ever the fluctuation of commodity prices are a concern for any manufacturer of feeds.

This flexibility also provided a possibility of developing feeds for a much more diverse range of Aquatic species from Tilapia to Trout, from Shrimp to Sea Urchin. Developing an industry that could expand from Fresh Water now to Marine Aquaculture with off shore facilities.

The door was opened to expand the Aquaculture industry not just in flexibility but enabled the transference of Extrusion Technology to other regions of the world to overcome challenges such as water temperature and changing salinity levels.

At the same time in bringing this advanced technology into the Aquaculture industry it also meant a steep learning curve to turn what was initially a low tech approach to produce Aqua Feeds to a more dedicated, food orientated process, that required new disciplines and a higher degree of control and consistency to achieve exact specification of the feeds for sink or float, water stability and durability.

Particle size reduction.

This extremely important first stage of the process required a higher control regards particle size consistency to provide a narrow grist spectrum with nominal sizes of 500 Micron and less, to achieve the quality and appearance which the industry has now come to accept as standard.

In some cases recipes containing up to 50% fish meal and only 10% starch require new efficient grinding systems to handle and maintain consistent grist size.

The effect of poor size reduction will manifest itself in low efficiency of cook, poor moisture equilibration in the preconditioning stage of the extrusion process and thus culminating into detrimental effects with regards to pellet durability and physical appearance.

The extrusion process provides the opportunity to determine cell structure in the extrudate, which in turn affects the capability of the pellet to accept medium to high fat levels. If the particle size is too large or the grist spectrum too wide the potential of adding fat or oil is greatly reduced.

Extrusion to meet today’s demands.

Since the first wet Extrusion system developed by LaVon Wenger back in 1957, today’s emphasis on reduced complexity and computer control have changed the perception and possible achievements that can be made at all levels of the aqua culture industry, whether producing high density feeds at over 600 grm/ltr or low density 120 grm/ltr , high fat, low fat, feeds from 0.8mm to 30mm, an extrusion system is available to provide this opportunity.

A standard system generally consists of the following.

1) Live bin – to ensure homogenous mix of the recipe before entering the extruder.

2) Feeder – to ensure controlled metering of the raw materials.

3) Preconditioning – to provide high levels of mixing with possible liquid addition in the form of fats/oils and steam to provide thermal energy and start the cooking process, average retention in this vessel is 2.5 minutes, cook possibilities 40-45%

4) Single or Twin Screw barrel – to exert mechanical shear and possible high pressure steam addition to reach cook levels of over 90% and finally form the extrudate into a pellet form.

5) Knife – to cut the final form, which will be transported to the drying process.

6) Dryer Horizontal / Vertical – to reduce the extrudate from a moisture content of approximately 24% - 10% for acceptable storage levels.

7) Coating system, atmospheric or Vacuum- to add external liquid coatings from 2% to 40%.

8) Cooling system – to finalize the process bringing down the temperature to an acceptable level and providing a short retention time to ensure absorption of coating.

This is of course a very simplified version of what can be a more complicated operation.

As always working with a manufacture of extrusion systems support is crucial and critical to success. Ease of operation, correct training and nutritional support brings the entire necessary package together to ensure success.

Understanding the local raw materials, species to be fed and range of feeds to be produced will provide an important consultative role to ensure the producer has a platform to work form and opportunity to expand in terms of capacity and flexibility for future business opportunities.

Energy consumption is an issue of significant importance in today’s increasing rising energy costs. With the combination of thermal and mechanical energy reduced operating costs can be achieved together with the flexibility of using the energy mix to obtain the characteristic requirements of the Aquatic Feed to be produced.


We in the Aquatic industry whether feed producers, Fish Farmers or equipment producers, must appreciate the need for self-regulation.

This in the form of providing feeds of the highest nutritional value, with ingredients that has potential to reduce the nitrate levels, provide efficient FCR values, are water stable, durable and pathogen free.

Result, an industry that will expand be welcomed, supplying a valuable protein source to ever increasing and rising populations, that have environmental respect an human values of responsibility.

This can only be done if we have a maintainable and sustainable practice that is adhered to throughout the Aquatic Industry.

We at Wenger Manufacturing are working with you to ensure we live up to your exacting standards in performance, energy efficiency and social demands in exciting progressive times within the Aqua Feed market.