8th International Symposium on Tilapia in Aquaculture 2008 725
FEED QUALITY AND NUTRITIONAL BENEFITS UTILIZING
Wenger Mediterranean Regional Division Manager.
There are a number of identified objectives when producing commercial aquatic feeds
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
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
The next stage pelletisation was a positive step forward providing
1) Increased Density and consistency
2) Improved storage.
3) Less Feed Waste.
FEED QUALITY AND NUTRITIONAL BENEFITS UTILIZING EXTRUSION TECHNOLOGY.
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
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
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
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.
FEED QUALITY AND NUTRITIONAL BENEFITS UTILIZING EXTRUSION TECHNOLOGY.
7) Coating system, atmospheric or Vacuum- to add external liquid coatings from 2%
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
This is of course a very simplified version of what can be a more complicated
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.