Note: Descriptions are shown in the official language in which they were submitted.
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FEED FOR FARMED FISH AND FOR FISH STORED IN A LIVE CONDITION,
AND A METHOD OF PRODUCING SUCH FEED
The invention regards a soft feed for fish, e.g. for feeding
farmed fish and fish caught alive and kept alive in netpens
or closing nets or other suitable devices. More particularly,
the invention regards an extruded and pelletized feed which
when soaked in water and subjected to a mechanical influence
loses its structure, forming a pasty, coherent soft mass.
This pasty mass may be formed into desired portions for fish,
lo either manually or by extruding the mass through a suitable
orifice.
In several types of fisheries the fish is caught alive, and
for many years the practice has been to shut this fish in by
means of nets while waiting to take the fish out of the sea
or the water. An example of this is the sprat (Sprattus
sprattus) fishing in Norwegian fjords, where the fish is
secured in a net and stored alive in seines while waiting for
a receiving vessel to retrieve the fish from the sea.
Securing the fish like this, or storing it alive, is
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necessary to make the fish empty its bowels, thus improving
its keeping quality up to the processing stage.
It has also become customary to store other species of fish
in a live condition. The advantage of this may be the ability
s to regulate the market, providing a more regular supply of
wild caught fish, thereby obtaining a better price for the
fish. Another advantage is that smaller fish with a lower
market value can be fed to obtain bigger fish with a higher
market value. This can be combined with delivering the fish
io out of season, thus achieving an even higher price. This type
of practice has been established for live caught cod (Gadus
morhua), pollock (Pollachius virens), southern blue-finned
tuna (Thynnus maccoyii) and northern blue-finned tuna
(Thynnus thynnus).
15 After the fish has been caught alive it may be transferred to
seines or netpens of the same type as that used for farming
of salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss),
sea bass (Dicentrarchus labrax) and axillary seabream (Sparus
auratus). Thus the technology for this is well known and
20 tested.
Farmed fish, including farmed cod and halibut (Hippoglossus
hippoglossus), are accustomed to a dry formulated feed from
the moment it has used up the nutrition in the yolk sac, or
possibly following a short period of being fed algae,
25 rotifers, and possibly brine shrimp (Artemia). Such fishes
will therefore accept a dry formulated feed as food, and will
grow well on this type of feed. The degree of utilization of
the feed is high, as very little of the feed introduced will
sink through the netpen and go to waste.
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A formulated fish feed here means a feed composed of one or
more sources of protein, including but not limited to marine
proteins such as fish meal and krill meal, vegetable proteins
such as soy flour, rapeseed flour, wheat gluten, corn gluten,
lupine flour, pea flour, sunflower flour and rice flour, and
slaughterhouse waste such as blood meal, bone meal, feather
flour and chicken flour. Mixing different sources of protein,
each with a separate composition of amino acids, makes it
possible to achieve a desired amino acid profile for the
io feed, suited to the species of fish for which the feed is
intended. A formulated feed further includes a source of
energy in the form of e.g. fish oil and/or vegetable oils
such as rapeseed oil and soybean oil. A formulated feed also
contains a binding agent, ordinarily in the form of
farinaceous (starchy) ingredients such as wheat or wheat
flour, potato starch or tapioca flour, peas or beans, in
order to give the feed the required solidity and stability of
shape. Furthermore, a formulated feed will contain the
minerals and vitamins required to ensure good growth and good
health for the fish. Moreover, the feed may contain
additional additives such as e.g. colouring agents to achieve
certain effects. Thus a formulated fish feed is a composite
feed in which the quantitative proportions of proteins, fats,
carbohydrates, vitamins, minerals and any other additives are
calculated to suit the nutritional needs of the species,
based on the age of the fish. Ordinarily, only one type of
feed is used, and so each piece of feed is of full
nutritional value.
A dry formulated feed here means a feed of a pressed or
extruded type. A pressed feed will normally contain less than
approximately 10% water after pressing and possibly the
application of oil. An extruded feed will contain between 18
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and 28% water following extrusion. After being extruded this
feed goes through a drying step, and subsequently an oil
application step. Like the pressed feed, the final product
will contain approximately 10% water or less, and as a result
will be highly storable, as the water activity in these feeds
is low so as to prevent the growth of mould and fungus, and
also avoid bacterial decay.
Dried and pressed or extruded feed may be of different shapes
and sizes. A common shape is a cylindrical piece of feed
io where the length-to-diameter ratio is normally between 1 and
1.5. Such pieces of feed are termed pellets. The size of the
pellet is proportionate to the size of the fish, thus the
diameter of the pellet can be between 1 and 30 mm. In
practice, the fish feed industry has found it difficult to
produce feed pellets of a diameter larger than 30 mm. The
difficulties associated with drying such pellets in
reasonable time are cited as one problem. Another problem is
the lack of solidity, which causes a lot of dust and
breakage.
A dry pressed or extruded fish feed will retain its shape in
water for several hours and up to several days unless
subjected to external mechanical influences. This is due to
the fact that the pellet contains a binding agent in the form
of starch. The binding agent has been added to provide the
pellet with sufficient strength to allow it to be stored and
transported in e.g. big bags that hold from 500 kg to 1000 kg
of feed, or to tolerate storage in feed silos and pneumatic
transport through production plants, during loading and
unloading, and between the feed plant and the individual
netpens. The dimensional stability in water is also partly
due to the pellet being covered in fat, leaving an external
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oil film, and possibly also oil-filled pores and cavities, to
inhibit the ingress of water.
The pellet will disintegrate after a period in the water,
forming a loose granular mass. This process can be
5 accelerated by subjecting the pellet to external mechanical
loads. On a laboratory scale this may be done by stirring the
water or directly squeezing or picking at the pellet. The
water and pellet will form a grainy thin paste consisting of
large and small particles.
Ordinary pelletized feed that has merely become moist will
loose its shape when squeezed, but will still break up into
individual pellets when the pressure ceases. When subjected
to harsher mechanical treatment it will break up into large
and small pieces but will not form a coherent mass.
Live caught fish has fed on various types of prey and is not
used to eating a dry formulated feed. The dry formulated feed
differs from the prey in shape, colour, consistency, smell,
taste and movement, and so it has turned out that live caught
fish needs a transitional period or adaptation period before
it accepts a dry formulated feed as food. In some cases, the
attempt to make the fish adapt to such feed is entirely
unsuccessful. An example of this is the southern blue-finned
tuna. This fish weighs around 15 kg when caught and is sold
at a weight of between 30 and 60 kg. Ordinary feed pellets
with a diameter of between 10 and 20mm are too small for the
fish to care about, in addition to which such feed pellets do
not have an appetizing texture.
In the period before the live caught fish accepts the feed
there is no growth, and the fish loses weight. This means a
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longer period before slaughtering and will also increase the
running costs, as the reduced weight will have to be
recovered by use of bought feed resources.
It has proven easier to make live caught fish accept the feed
if this has a soft consistency. A soft consistency is
achieved by having a significantly higher content of water
than the approximately 10 % found in dry feed. A soft feed is
basically a paste which can contain all of the required
nutrients, and which is formed into pieces of feed, manually
io or by extruding it through an orifice e.g. in a sieve plate.
Presumably it is the soft texture that makes this feed more
acceptable to the fish than dry feed. After the fish has
become accustomed to a soft feed this feed can continue to be
used until the fish has reached the desired size.
Alternatively the fish can adapt to a dry formulated feed
after accepting the soft feed as food.
Soft feed, also called semi-moist feed, is commonly used in
fish farming. In particular, it is common for the farmer to
prepare the feed himself during the early development phase
of the fish farming. Such feeds typically contain 40 % water
or more. Upon changing to a more industrialized form of fish
farming the soft feed is replaced by industrial feed of the
pressed or extruded type.
Soft feed is normally made from whole fish, chopped fish or
fish offal. This is mixed with a binding agent, often in the
form of starch, but also alginates, and possibly fish oil or
other cooking oils, and possibly also vitamins, minerals and
other required additives, in a grinder and shaped into pieces
of feed by extruding this through a sieve plate. The size of
the feed pieces is generally determined by the diameter of
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the orifice. Alternatively the paste may be shaped into feed
pieces manually.
The raw fish materials are obtained frozen or fresh. Frozen
raw fish materials may be thawe'd before grinding, but some
types of grinders can also grind frozen fish. The dry raw
materials such as binding agents, vitamins and minerals can
be mixed in advance and come as so-called premixes. It is
also possible to mix in dry protein materials such as
fishmeal, and wet protein materials such as e.g. fish
io ensilage.
An alternative to soft feed is to feed the caught live fish
with whole fish or bits of fish. This may be fresh fish or
frozen fish that is thawed immediately before feeding. Some
fish farmers let whole blocks of frozen fish float on the
is water. As the block thaws, the fish or pieces of fish fall
off and become available as food.
In Japan it is known to get live caught yellow tail (Seriola
lalandi) accustomed to an extruded soft feed. This feed is an
extruded feed with a relatively low fat content. Prior to
20 feeding, this feed is soaked in water to allow the pellet to
absorb water. The pellets can absorb from 50% to 150% water
relative to its own weight. The soaking can take from 5
minutes to an hour. After being soaked, the pellets are soft
and flexible but still distinct pellets, and they are fed to
25 the fish as regular pellets.
When producing fish feed by means of an extruder the
extrudate contains a maximum of 30% water. Prior to drying,
this extrudate is soft and flexible. It is known for this
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extrudate to be preserved through freezing instead of drying.
The farmer will then thaw the feed prior to feeding.
It is also known to produce fish feed by partly adding
various water binding agents and partly various softeners.
Glycerol is an example of such an additive.
In the case of a dry formulated feed it is a problem when the
caught fish does not accept the feed as food. Getting on with
ordinary feeding can take a long time. During this time,
there is no growth and the fish may even lose weight. The
feed used in order to make the fish adapt to the dry feed is
largely lost. This is unprofitable to the farmer and
detrimental to the environment, as unconsumed feed can settle
on the seabed, causing a deterioration of the environment.
Use of a soft feed, whole fish or pieces of fish does not
carry the same disadvantages as use of a dry feed in terms of
the time taken for the fish to get accustomed to it. On the
other hand, it is more labour intensive, as it must be
produced on-site and has a short shelf life. Soft feed
requires either a regular supply of fresh raw materials or
access to frozen raw materials. A regular supply of fresh raw
materials may be made difficult by seasonally conditioned
fisheries. Poor weather conditions will also affect the
availability. Alternatively use can be made of frozen raw
materials, which requires access to cold storage. The same
holds for the availability of whole fish or pieces of fish.
An additional disadvantage of a soft feed is the fact that it
is not formulated. It is especially difficult to control the
ratio of proteins to fat, and the amino acid profile is
determined by the raw material. The same applies when using
whole fish or pieces of fish.
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A soft feed is compact, and it is difficult to control the
density of the feed. A soft feed will sink quite quickly in
water compared with a dry formulated feed of the extruded
type. This means that there will be a greater waste of soft
feed compared with dry extruded feed in situations where the
fish has become accustomed to the respective types of feed.
Frozen extruded feed requires an unbroken chain of
refrigerated transportation means from the producer to the
farmer. This requires more expensive and more complex
logistics than the transportation of a dry feed. The simplest
and cheapest way of freezing feed pellets is to package the
feed in bags, e.g. 25 kg bags. The bags are then placed in
cold store. Fish feed has good insulating properties, and so
it takes time for a bag to become frozen through. In some
is instances the core does not freeze and a lot of fungus, mould
and bacteria will develop at the centre of the bag during
storage and transport. This will not become apparent until
the bag is thawed and opened, when the damaged feed mixes
with the rest of the feed. An alternative method of freezing
is to freeze the pellets prior to packing, by using e.g. a
tunnel freezer. This technology raises the price of the
product.
Adding water binding and softening components such as
glycerol makes the product more expensive. Known mould
inhibitors and bacteria inhibitors such as propionic acid and
benzoate can also be added in order to give the pellets
better storage stability at room temperature. All such
additions make the product more expensive. It is also
important to remember that such additives must not reduce the
tastefulness of the product. Thus fish is known to react
negatively to feed containing propionic acid.
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A known method of increasing the storage life of moist
products is to package these in a modified atmosphere or
vacuum-pack them. This makes certain demands on the packaging
and requires dedicated packing equipment.
The object of the invention is to remedy or reduce at least
one of the drawbacks of prior art.
The objective is achieved by features described in the
description below and in the following claims.
The object of the invention is to arrive at a fish feed which
is soft when fed out to fish, especially caught fish, while
at the same time retaining the beneficial properties of the
extruded dry feed in terms of formulation relative to the
specific requirement of the fish in question, and the simple
logistics associated with the extruded dry feed, from
producer to fish farm.
It is also an object of the invention that the soft feed
shall be adaptable to different sizes of fish, and
advantageously it is possible to form larger pieces of feed
than that which is possible in conventional fish feed
production based on extruder technology.
Soft feed refers to a feed containing more than 15 % water.
In particular, it refers to a feed containing more than 20 %
water, and a water content of more than 30 % is even more
beneficial to the soft texture. Feed containing more than 30
% water cannot be produced by use of conventional extruder
technology. Such a soft feed has a texture that is beneficial
when it comes to making live caught fish adapt to a
formulated feed.
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Surprisingly, it has turned out that by using known raw
protein materials such as e.g. fish meal, krill meal, soy
flour, rapeseed flour, wheat gluten, corn gluten, lupine
flour, pea flour, sunflower flour, rice flour and
slaughterhouse waste such as blood meal, bone meal, feather
flour and chicken flour, and by using binding agents
containing starch, such as e.g. wheat, peas, beans, potato
starch or tapioca flour, and by using fats such as fish oil
or rape seed oil, it becomes possible to produce a pelletized
io fish feed having a new technical property, the feed pellets
forming a soft coherent paste after being soaked and
subjected to simple mechanical kneading. To this end use is
made of an extruder which in terms of pressure and
temperature conditions and the ratio between thermal and
mechanical energy is set so as to make the starch in the
extruded material exhibit the properties required for the
feed pellets to exhibit the desired novel property of forming
a soft coherent paste. This paste may be shaped into pieces
of feed of a desired size by pressing it through a suitable
orifice in e.g. a sieve plate or by manual shaping. Such
shaping makes it possible to achieve larger pieces of feed
than those that can be achieved in the production of dry
extruded pellets.
The feed is produced by the dry raw protein materials and
binding agents being ground and mixed with vitamins and
minerals and any other desired components. This mixture is
passed through a known preconditioner in which steam,
possibly water, possibly oil and possibly fish silage is
added to the mixture before it passes into a known extruder
such as a single screw or double screw extruder. Here, the
mixture is worked, and any additional steam, water, oil or
fish ensilage is added here, so as to impart the intended
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property to the starch fraction before the mass is forced out
through the die base and the extrudate is cut to the desired
length by a rotary blade. The holes in the die base may be
between 1 mm and 25 mm. The desired length may be shorter
s than the diameter of the pellet and up to twice the length of
the pellet, or longer if expedient. The water content of the
extrudate may be between 18 and 28 %.
After being cut, the extrudate passes through a known dryer,
e.g. a vertical drying tower or a horizontal belt dryer, and
io is dried to a water content of less than 10 %. Following
dehydration, more oil may if so desired be applied to the
pellets by use of known techniques, e.g. a vacuum coater.
Following dehydration and any application of oil, the pellets
are cooled in a known manner, sieved free of dust and
15 particles and packaged.
Prior to being fed out, the desired quantity of dry extruded
feed in accordance with the invention is placed in a suitable
receptacle and liquid is added to the pellet. The term
suitable receptacle also refers to e.g. a bag or other
20 packaging such as the packaging in which the feed is
delivered.
Preferably the quantity of liquid added to the dry pellet is
not more than that which can be absorbed by the pellet, while
at the same time being sufficient to give a pasty
25 consistency. Preferably the amount of added liquid
constitutes between 20 % by weight and 200 % by weight of the
pellet. More preferably the amount of added liquid
constitutes between 25 % by weight and 100 % by weight of the
pellet. Even more preferably the amount of added liquid
30 constitutes between 30 % by weight and 80 % by weight of the
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pellet. Most preferably the amount of added liquid
constitutes between 30 % by weight and 60 % by weight of the
pellet.
The liquid may be fresh water, seawater, fish ensilage, size
water or another protein containing liquid such as a mixture
of water and fish entrails, or a mixture of two or more such
liquids. The temperature of the liquid may be the same as
that of the surroundings or it may deviate from this.
Hereinafter the term "liquid" refers to a liquid composition
of one or more of said liquids and materials.
Preferably the soaking time is between 1 minute and 24 hours.
More preferably the soaking time is between 1 minute and 12
hours. Even more preferably the soaking time is between 1
minute and 6 hours. Most preferably the soaking time is
between 1 minute and 90 minutes.
After soaking, the soaked feed is worked into a coherent soft
paste. The working may be done by a rotary arm or screw
located in the receptacle, or by lowering a suitable device
into the receptacle. When the paste has achieved the desired
consistency it may be removed and transferred to a suitable
apparatus for shaping the pieces of feed. Such a suitable
apparatus may be a simple grinder in which an auger carries
the paste through one or more suitably sized and shaped
orifices in a sieve plate. The length of the pieces of feed
can be decided by means of a rotary blade, or by the string
breaking off under its own weight.
Alternatively the soaked but still distinct pellets may be
transferred to a suitable device for working the pellets into
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a mass. Such a device may be a grinder. Working (kneading)
and shaping the feed into pieces will then be carried out in
one operation
Alternatively there may be associated with the mixing
receptacle an arrangement having one or more suitably sized
and shaped orifices. The paste in the mixing receptacle can
for instance be pressed against the orifice arrangement by a
suitable device such as a rotary arm that presses the paste
against the wall of the receptacle. Outside the receptacle
io the paste may be cut into suitable lengths or the string of
paste will break off under its own weight. Still other
arrangements can be envisaged, which would achieve the
desired mechanical working of the soaked feed in accordance
with the invention.
is An alternative method involves mixing whole fish or fish
offal in with the dry pellets prior to soaking, or mixing in
whole fish or fish offal after soaking but prior to working
or kneading to form a paste, or mixing fish or fish offal
into the prepared paste before shaping pieces of feed through
20 a sieve plate.
A person skilled in the art will know that the preparation of
the paste and the shaping of the pieces of feed can take
place on shore or on a floating structure, and that the
pieces of feed can be transported to the netpens in a known
25 manner and be distributed in the netpen in a known manner.
Alternatively a person skilled in the art will know that the
preparation of the paste and the shaping of the pieces of
feed can take place in direct connection with the netpen,
such that the shaped pieces of feed will fall directly into
30 the netpen or is distributed across the surface of a netpen
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or in several adjacent netpens by means of simple devices.
Alternatively a person skilled in the art will known that the
paste may be prepared in one place and the pieces of feed
shaped in another place, all depending on what is most
5 expedient.
The following describes non-limiting examples of preferred
embodiments.
Example 1
A feed in accordance with the invention was prepared
10 according to the following recipe:
Whole-wheat ................. 19 kg
Fish meal ................... 51 kg
Krill meal .................. 5 kg
Corn gluten ................. 8 kg
15 Wheat gluten ................ 6 kg
Fish oil .................... 11 kg
Following grinding and mixing of the dry raw materials, these
were preconditioned in a Wenger DDC preconditioner and
extruded in a double screw extruder (Wenger TX-57) at a feed
rate to the preconditioner of 140 kg per hour (dry material).
13.8 kg per hour of steam and 26.1 kg per hour of water were
added to the mass in the preconditioner. The mass held a
temperature of 87 C upon exiting the preconditioner. 7.7 kg
per hour of water and 17.0 kg per hour of fish oil were added
to the extruder. The specific mechanical energy was 26.9
kWh/ton and the specific thermal energy was 43.0 kWh/ton. The
pellet diameter was 3 mm. The pellet was dried in a belt
dryer with three sections, the air temperature in the
sections being 80 C, 80 C and 70 C, respectively. The total
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drying time was 13 minutes.
The dry feed contained 54 % protein, 17 % fat and 5 % water.
The produced feed was soaked for about 20 minutes at a ratio
of 6 kg of water to 10 kg of feed. A web of spaces had formed
between the loose pellets, allowing the water to distribute
easily and all the pellets to soak. After soaking it was
easy to form a soft paste by kneading the feed by hand. The
feed paste contained approximately 40 % water, approximately
34 % protein and approximately 11 % fat. Alternatively the
produced feed was soaked for about 30 minutes at a ratio of 9
kg of water to 10 kg of feed. The feed paste contained
approximately 50 % water, approximately 28 % protein and
approximately 9 % fat.
The wet feed pellets were also worked by an ordinary mincer.
Soft spaghetti shaped strings were formed after passing
through the sieve plate of the mincer. The shaped pieces of
feed exhibited a good ability to sink in water and were
stable in water for a period exceeding the time it takes for
feed to sink through a netpen.
Example 2
A feed in accordance with the invention was prepared
according to the following recipe:
Fishmeal .................. 49.1 kg
Hipro Soya ................ 8.3 kg
Wheat ..................... 20.3 kg
Wheat gluten .............. 6.0 kg
Fish oil .................. 10.7 kg
Full fat fish ensilage .... 5.0 kg
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Betanin ................... 0.04 kg
Minerals .................. 0.09 kg
Vitamins .................. 0.09 kg
Following grinding and mixing of the dry raw materials, these
were preconditioned in a Clextral preconditioner and extruded
in a double screw extruder (Wenger TX-144) at a feed rate to
the preconditioner of 3 tons per hour (dry material). 6 %
steam, 10 % water and 5 % ensilage were added to the mass in
the preconditioner. 9 o water was added to the extruder. The
pellet diameter was 3 mm. The pellet was dried in a belt
dryer. Oil (10,7 %) was added after drying in a vacuum
coater.
The dry feed contained 47.6 % protein, 17.7 % fat and 10.6 %
water.
After soaking, the feed was worked into a paste and pieces of
feed were shaped by rolling the paste by hand, into pieces
having the sizes of golf balls and tennis balls. These pieces
of feed were given to live stored pollock. The pollock had a
weight of between 300 and 400 g. Compared with feeding of
ordinary dry extruded feed, the pollock displayed a great
appetite. Pieces of feed the size of golf balls were eaten
whole, while the pieces of feed the size of tennis balls were
eaten piecemeal.
A soft feed in accordance with the invention can be used for
feeding farmed fish that has lived all the stages of its life
under controlled conditions.
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Another application is recreational fishing, where the pasty
feed can be used as bait on a hook. It may further be used as
bait to attract wild fish to a baited hook, by throwing small
pieces of feed out into the water around the fishing spot.
s The pasty feed may further be used by professional fishermen,
as bait on hooked fishing equipment and as bait in fishpots,
fish traps and other stationary fishing gear.
It is a novel idea to produce an extruded pelletized fish
feed consisting of standard feed ingredients in the form of
protein, fat, carbohydrates, vitamins and minerals, which
feed upon soaking in water exhibits the quality of being
able, after simple mechanical working of the pellets, to give
a coherent soft paste that can be shaped into pieces of feed
having the desired cross section and size. The shaping is
achieved by in a known manner pressing the paste through a
sieve plate having one or more suitable orifices,
alternatively by manual shaping. The produced pieces of feed
are suitable for making stored live caught fish adapt to
formulated feed.
