Fish Feed Production from Local Feedstuffs
Ozochima Victor Chima
By
1993 it was becoming clearer that fishing from the wild cannot sustain
fisheries needs in Nigeria Nigeria Nigeria Nigeria
In
terms of nutrition, fish can be broadly grouped into, carnivores for fish that
feed on other animals, herbivores for those that feed on algae and other plants
and omnivorous for those that feed on plant and animal materials. The feeding
habit of fish is usually considered when producing feed for the species. Again,
larval fish are fed differently compared to other fish. Feed production is to as far as possible, take
care of the gastronomic habits of the target fish. This is done by preparing feeds that meet the
specific nutritional and physical property needs of the fish. The production
has to recognize the slow feeder, the fast feeder, surface feeder, mid water
feeder and bottom feeder.
Below are terms
used in nutrition of most cultured fish.
1.
Fish feed is
that material given singly or in combination to fish which may not be
necessarily what it consumes in nature.
2.
Fish food on
the other hand, is the edible material which fish choices to consume in its
natural environment to furnish nutrients to the animal. At times, however, the
term fish food is used to include both prepared diets and natural nutrients. We
will stick with the first definition.
3.
A diet is
any substances prepared as nutritional substitute for fish food.
4.
A nutrient
is a dietary constituent of feed or food that aids in the growth and the
support of life processes.
5.
Ration is a
24-hour diet allowance for the animal. A material or mixture of
materials to make an allowance for 24
hours.
Some principles to be considered in
aquaculture include:
1.
Fish is poikilothermic i.e. cold-blooded animals and
its energy of metabolism differs from those of homoeothermic (warm-blooded)
animals. Fish does not need as much
energy for metabolism. Commercial diets used for some important species of fish
such as channel catfish for grow-out purposes as a result usually contain 32%
crude protein and 3.0 kcal digestible energy (DE)/g of diet, for a digestible
energy : protein ratio (DE/P) of 9.4 kcal/g of protein (Reis et al., 1989).
2.
Carbohydrate is more poorly digested in most fish than
in land animals. A lot of carbohydrates feed is excreted. Recent
research, however, have shown that Clarias
spp. efficiently utilize non-protein energy from carbohydrates and can
improve protein retention (Luquet and Moreau, 1990).
3.
In protein metabolism nitrogen is excreted by most fish
as free NH3 in water. About
80% of excess nitrogen is excreted as NH3. In terrestrial animals, excess nitrogen is
excreted in urine and this process requires energy. The nitrogen is excreted as urea and hence a
loss to the animal in the form of carbon, oxygen and hydrogen which are
excreted with every molecule of nitrogen. Fish is therefore more efficient in excretion
of nitrogen needing less energy and wasting fewer materials.
4.
There is no danger of overfeeding in land animals. Over feeding in fish affects the water
quality. Floating feed is an advantage
in pond feeding, though slightly more expensive than sinking pellets, because
the fish can be seen feeding and how much feed to offer to the fish without
wastes can therefore easily be determined (Mgbenka and Lovell, 1984).
5.
Fish absorbs dissolved nutrients such as Ca++,
out of the water. Inorganic phosphates (PO42-) are not
much found in water. Phosphorus is bound
up in the bottom mud hence the need to fertilize ponds especially when the
secchi disc visibility exceeds ≥ 45 cm. Most
organic and inorganic materials are picked up across the gills into the blood
stream. Nutrients which are not picked up or
manufactured by fish at all or insufficient quantities in culture condition are
supplemented in the feed e.g. vitamins and minerals.
6.
For a high percent crude protein diet we require high
percentage of protein supplement feedstuff in the finished diet and vice versa
for low percent crude protein diet.
Feedstuffs or feed ingredients
Feed
ingredients are chosen so as to satisfy the protein and energy
requirements of the target
species for which feed is made; essential minerals and vitamins are always
added as supplements. As a result of this feedstuffs are broadly classified as protein or basal feedstuffs. For
production of feed on farm the choice of ingredients should be such that they
provide protein, carbohydrate and fat at less expense without sacrificing
meeting amino acid requirements of the target species.
The
major local feedstuffs that meet the protein needs of most species without
sacrificing amino acid requirements are corn, soybean meal and fishmeal. Using
these ingredients in combination in fish diets ensures that what amino acid
that is lacking in one feedstuff is augmented by a relative excess in the other
e.g. low methionine in corn is synergistically replaced by that in soybean
(Lovell, 1989). These feed ingredients
are, however, expensive for their use in fish competes which human and livestock
feeds. Trash feed can be used as is
practiced in Asia (Jantrarotai and
Jantrarotai, 1993) for making catfish and carnivorous fish feeds but the use is
limited to farmers living on the coast and there may be use of treatments such
as pasteurization to kill potential human pathogens such as Salmonella spp. The high expense of these conventional
feed ingredients demands that other unconventional ingredients be used for fish
feeds. Even fishmeal has got so
expensive that substitute ingredients to fishmeal have been sought (Viola et
al., 1982). Charred fish fines of less
human nutritional appeal shown to be good as fish feed ingredient for cash-strapped
and cannot go for better feed ingredients (Mgbenka and Agua, 1990). Presently, there are several unexplored unconventional
feedstuffs which would not compete stiffly with human or livestock diets.
Oyenuga
(1968) did extensive work and reported that nutrient contents of many Nigerian
feedstuffs. These include those used for
human and livestock nutrition and some unconventional feedstuffs such as peels,
some roots/tubers e.g. cassava, cocoyam, sweet potato root, yam; some leaves
e.g. sweet potatoes, cassava, sugar cane, Telfairia;
some concentrates e.g. Acha grains (Digitaria exilis Stapf.), bambara groundnut,
cocoa beans, cotton seed, groundnut cake, guinea corn grain, millet (bulrush’s
grain), Mucuna seed (Mulcuna spp.
Adams), Palm kernel cake, rice bran, whole soyabean, sunflower seed, yellow
maize; dried leaves hay and husk e.g. cowpea husk, cocoa husk, green gram husk,
rice husk, ground nut husk; and even miscellaneous ingredients of which some
are relatively high in crude protein
(CP) e.g. plantain peels ripe (CP, 9.14%), plantain peels unripe (CP, 10.64),
pawpaw leaves (CP, 32.6%), mango green fruit (CP, 35.0%) blood meal pure dried
(CP, 88.46), blood meal mixture (CP, 33.72). Only estimated digestible nutrient values were
given for the feedstuffs reported by Oyenuga (1968). Other unconventional ingredients have been
used for Clarias gariepinus e.g. toad
meal (Annune, 1990). Elsewhere, other
conventional material like earth worms which abound in Nigeria
To
produce efficient fish feeds there is need to determine digestible nutrient
values of local ingredient to fish. Only
very little work is done in digestibility of feedstuffs to Nigerian fish species
(Mgbenka and Agua, 1990). Again, some plant proteins e.g. soybean meal, most
other legumes have been reported to have anti-nutritional factors such as protease
inhibitors and lectins (Liener, 1980) and some may need heat treatments to
denature the factors. Also, some plant ingredients are deficient in
certain essential amino acids such as methionine, tryptophan and lysine which
are required for good growth in fish (Moses, 1983), while yet others e.g. sorghum,
most grains have phytic acid which ties up phosphorus in the form of phytate
phosphorus which is poorly available to fish, reduces bioavailability of zinc
and other elements and depresses protein digestability thereby resulting in
poor growth (Christenensen, 1981; Lovell, 1989). Feedstuffs such as coffee pulp and sorghum
have tannins which lead to poor growth in fish when supplemented at high
levels. This dictates the need for
additional supplementation of feed with phosphorus in such forms as dicalcium
phosphate in all-plant fish diet (Lovell, 1989, Mgbenka and Ugwu, 2005; Ugwu et al., 2005). Other toxins which preclude the use of
unconventional feedstuffs in fish feeds include gossypol, cyclopropionic acid (Lovell, 1989) enzyme inhibitors and
aflatoxins (De Silva and Anderson, 1995). Gossypol in cottonseed meal is moderately
toxic to non-ruminants such that only 7.5% - 15% solvent processed cottonseed
meal is recommended in fish diets. Treatment of 0.85 to 1.0 part ferrous sulphate
to 1.0 part free gossypol has been reported to block the toxic effects of
gossypol in monogastric swine (Tanksley, 1970) and possibly in fish. All varieties of cottonseed meal have
cyclopropenoic fatty acids which causes a lot of complications in fish
rendering the use of cottonseed meal risky. Animal protein sources e.g. poultry and farm
animal offal are more scare but where available as in the case of some integrated
farms, they can be used for on-farm fish feed production. Some care and proper treatment have to,
however, be exercised when feedstuff are selected for making fish feeds to
ensure that wholesome ingredient without disease agent are selected.
Feed formulation
Nutrition
performance and success of artificial diet for aquaculture depends to a great
extend on feed formulation and manufacturer, on-farm feed management
and aquatic environment.
Series of technical and economic
considerations in the formulation of feed are:
1.
The market value of the species to be fed: The
table size prize of the species should be considered so that in general the dry
diet cost should not be more than 25% of the market table size value of the
cultured species.
2.
The financial resources of the farmer (if home-made
fish feeds are to be produced):
The capital available for the
purchase of feed ingredients and
Feed manufacture and equipment and
availability of services
Such as electricity and fuel should
be considered.
1. Feed formulation and 2. Feed manufacture and
Nutrient content physical
characteristics
3. Aquatic environment &
Natural food availability 4. Feed
handling and Storage
5. Feed application method &
feeding regime
Fig 1. 5 Major factors determining the nutritional
performance
and
success of an artificial diet feeding regime (After Tacon, 1993)
3.
Dietary nutrient requirement of the species to be
fed (or closest
relative)
To include dietary protein, amino
acids, fatty acids, minerals,
Vitamins and requirements for such
phase of the culture cycle
(namely, for larvae/fry, juvenile
and brood stock productions (if
known).
4.
Natural feeding habits of the species in question
(if known)
When
such information is not available some insight on the dietary
nutrient
requirements can be gained from analysis of its natural
feeding
habits in the wild to indicate the position in the aquatic
food
chain (i.e. herbivore, detritivore, omnivore or carnivore),
preferred
food items and food size (i.e. plant and animal
feedstuffs),
feeding station (i.e. surface, mid-water or benthic
feeder),
and feeding behaviors (i.e. daylight or nocturnal feeder,
visual
or olfactory feeder, rapid or slow feeder, continuous or
intermittent
feeder). An analysis of the natural target species gives
an
insight as to the physical characteristics of the artificial diet to
be
produced (i.e. feed size and shape. Texture, palatability,
buoyancy
and water stability).
5.
Available feed ingredients, sources, composition and
cost
Seasonal
availability, current usage of the ingredients, proximal composition, quality
control, digestibility, nutrient availability, additional ingredient handling
and processing cost prior to mixing or pelleting need be considered before use
of a particular feed ingredient.
6.
Intended feed manufacturing process to be used
Grinding,
mixing cold pelleting, steam pelleting, hand moulding,
expansion
pelleting, flaking, and/or microencapsulation. Formulation will
depend
on whether the diet is to be produced as mash (meal), crumble,
paste,
ball, moist pellets or dry pellet.
7.
Intended stocking density and farm production
unit
Extensive,
semi-intensive, intensive systems with tanks, raceways, concrete lined ponds,
earthen ponds, pens or floating cages. The stocking density will determine the
relative natural feed organisms per unit biomass of cultured animal
(fish/shrimp). As a general rule the contribution of natural pond organisms to
the nutritional budget of cultured aquatic species will be highest at low
stocking densities or at the start of the culture cycle. At the start the total
biomass (standing crop) is lowest. Contribution
of natural food decreases over time during the production cycle with increasing
size of cultured organism and standing crop. This is true especially for
non-carnivorous fish species. In semi-intensive fertilized pond systems with
mostly non-carnivores fish species as the difference between the standing crop
of natural food organisms increases, the deficit in natural protein supply also
increases. Supplementation with protein-rich diet becomes necessary for the
latter condition to maintain growth in the system. Hepher et al. (1971) and Hepher (1975)
reported that the growth of common carp was not affected by a 9% crude protein
pelleted sorghum diet until at a standing crop of 800 kg/ha because natural
food was enough at a lower stocking density. It became effective in improving growth at 800
kg/ha only to become ineffective later when a 22.5% protein diet became
effective up to a standing crop of 1400 kg/ha and thereafter dwindled in
effectiveness. In intensive clear-water
systems where natural pond organisms play little or no role in the nutrition of
the organisms, the reverse is the case i.e. dietary nutrient levels are usually
decrease with increasing fish size and age.
Dietary energy
is usually the first limiting factor (nutrient) within earthen ponds at low
fish stocking density. As the stocking
density and standing crop increases, the requirement for supplemental dietary
nutrients such as protein, minerals and vitamins also increase. The dietary
protein and essential micronutrient of supplementary feeds intended for
semi-intensive aquaculture pond systems should be low at start and
progressively increased. In
semi-intensive systems abundant natural pond food organisms sufficed for the
needs of the cultured species at the beginning because many of them are rich in
protein hence the reduced level of inputs recommended at the start.
Some other points to note or things to seek out for when formulating
fish feed:
1.
Nutrient requirements of the species if known in
available – amino acids, lipids, vitamins. If not known those of related species can be
used.
2.
Protein (crude) requirements of the species. This varies from 30 – 55% for many fish
species. Invariably fish feeds are
balanced from protein content of the finished diet rather than for the energy
in the finished diet. This is so because
protein is usually the more expensive input in the feed.
3.
Based on the type of fish chosen the crude protein range
to work with e.g. for larval freshwater fish, 40% may be chosen for catfish;
herbivorous and omnivorous species usually require lower crude protein levels
e.g. 32% - 35% crude protein compared to ≥ 40% - 45% crude protein input for
carnivorous fish like snake fish (Chana
obscura) and shrimp.
4.
It is important to know the percentage nutrient levels
in the available feedstuffs. Nutrient
requirements tables from National Research Council (NRC), Washington DC
5.
Formulation of the diet should be started using any of
the available methods e.g. trial and error method or the Pearson’s square
method.
6.
For a high percent crude protein diet, we require high
percentage protein supplement feedstuff in the finished diet and vice versa for
low percent crude protein diet.
Through
digestibility and resultant availability of nutrients for any feedstuffs to
fish may be affected by such factors as temperature, meal size and possibly
body size, it is assumed that any nutrient in any particular feedstuff is just
as available as the same nutrient in another feedstuff i.e. low cost determines
which feedstuff to use. It is possible
to make infinite number of feed formulations to meet the nutritional
requirement of fish. Some of the simple methods used include:
i.
Pearson’s method,
ii.
Trial and error method,
iii.
Solving simultaneous equations
Pearson’s method (De
Silva, and Anderson, 1995)
In this method the formulation
can be done by balancing crude protein level, energy level or cost. Usually protein is used.
A. Balancing crude protein level.
Protein is usually expensive and
is the first nutrient to be computed for. Then energy level is adjusted to the desired
level with high energy supplements of lower costs. Fish
feed to meet energy requirement.
1.
For diet formulation using soybean meal (SBM) and rice
bran (RB) the square method (Pearson’s) can be used thus:
1.
Draw a square and diagonals of the square.
2.
Place SBM and RB at the left corners of the square with
their respective crude protein contents.
3.
Write down the desired crude protein content of the
diet at the intersection (middle) of the diagonals of the square.
4.
Subtract the protein level of the feed from those of
feedstuff and write answers at the right opposite diagonal corners from the
feedstuff. Ignore negative and positive
signs.
5.
Total up the values at the right hand corners.
6.
The proportion of the feedstuffs to mix is:
RB = 14000/358% = 39.1% of rice bran
SBM = 21800/358% = 60.9%
of SBM.
B.
For more than two feedstuffs available for formulation
these are grouped in such a way that those with crude protein (CP) < 20% are
regarded as basal feedstuffs while those with CP > 20% are regarded as
protein supplements. Average values of CP are found and as in the SBM – RB
above to calculate joint quantities of feedstuffs required. For example, to produce a 27% tilapia or
common carp diet or African bonytongue (Heterotis
niloticus) diet using rice bran, yellow corn (c) and SBM and shrimp meal (or
fish waste) as was reported by Pillay (1980).
Basal feeds required = 21.35/39.15
= 54.53% - - corn and rice bran. Protein supplement required = 17.8/39.15 =
45.47%
To make 100 kg of feed, the
different feed ingredients required will be:
Rice bran = 54.53/2 =
27.265kg
Corn = 27.265
kg
Soybean = 45.47/2 =
22.735kg
Shrimp meal = 22.735kg.
Some feed ingredients
e.g. fishmeal to be used in the diet may be fixed. For a 26% crude protein diet suggested by New
(1987) where fishmeal from previous experience was pegged at 10%, using
groundnut cake with 34.5% crude protein and rice bran with 13.3% protein, the
computation of quantity of ingredients to be used can be done thus:
Actual amount
of each ingredient should be:
Basal feed = 21.35/39.15 = 54.53%
Protein supplement = 17.8/39.15 = 45.47%
With rice bran and corn as basal feedstuffs and soybean mean
and shrimp meal as supplemental feedstuffs:
Thus, to make 100 kg of this feed one would mix the
following:
Rice bran 27.265 kg
Corn 27.265
kg
Soybean 22.735kg
Shrimp meal 22.735
kg
Usually it is advisable to start
with about three feedstuffs:
1. One
high in protein and high in ME
2. One
low or intermediate in protein and high in ME
3. One low or intermediate in both protein
and energy. It is needful to make
allowance or fix the level for feed additives (vitamins, mineral premix,
antioxidants (e.g. butyl hydroxyl toluene (BHT), Ethoxyquin, drugs, etc).
C. Later, levels of essential or indispensable
amino acids (AA) are checked to ensure that the levels meet the target species
requirement for amino acids. If the levels of arginine, lysine, methionine, and
tryptophan are met, it is most likely that the dietary requirements of other
six amino acids will be met. If unconventional protein supplements are used to
eke out low levels of amino acids in the feedstuff, the level of all the amino
acid should be checked. The ten essential amino acids include: Phenyl Alanine,
Valine, Threonine, Tryptophan, Isoleucine, Methionine, Histidine, Arginine,
Leucine, and Lysine. Feedstuffs that are
rich in the deficient AA are added at the expense of other ingredients. After this, the levels of protein and energy
are rechecked to ensure that they still meet the requirements for the species.
Advantage of this method:
1. It is easy i.e. simple to apply.
2.
It can be used to calculate proportions of feedstuff to
meet protein and energy levels.
Disadvantage
of this method:
It cannot be
used simultaneously to solve for both protein and metabolizable energy (ME)
levels.
Other methods
i. Best buy technique
For energy, the
best buy technique is also employed when considering which feedstuff to use. For example, if brewer’s waste cost N0.0858/kg; contains 1,2000 kcals ME/kg,
i.e. cost/kcal = 0.0875/1,200 = N0.0000715/kcal
and wheat middling waste costs N0.1883/kg
while containing 1,663 kcal ME/kg i.e. wheat middling costs N0.00001132/kcal. Hence, though brewer’s waste is lower in ME,
it is less expensive to use in terms of cost/kcal.
Similarly, for protein, if anchovy
fishmeal is at a cost of =N=0.5357/kg, and 70.9% CP and herring fishmeal at
=N=0.4709/kg, 76.7% protein, cost per kg protein = 0.470/0.767 =
=N=0.161395/kg. Hence, herring meal is better for use i.e. less expensive of
the two.
ii. Cost per unit of amino acid
Cost per unit of
amino acid can also be employed to compare feedstuffs. When using such comparisons, the availability
of the nutrients to the animal should be kept in view, where the nutrient is
not readily available to the fish in both feedstuffs, the comparison is not
valid.
Feed Processing
Feed processing operation can be
summarized to comprise of
1.
raw material size,
2.
raw material blending,
3.
feed forming and
4.
feed drying (Wood, 1995)
To effect these, equipment of
some form ranging from crude to sophisticated is needed. Some options in feed
processing are given in Table 1 below:
Table 1: Options for feed Processing
equipment
Process
operation
|
Equipment
|
Raw
material/product
|
Size
reduction
|
Mortar
and pestle
Mincer
Hammer
mill
Plate
mill
|
Dry
of moist grinding or blending
Wet
materials e.g.
Trash
fish/offals
coarse
– fine dry materials
coarse
– fine dry materials
|
Blending
|
Physical
Mechanical
mixer
Horizontal
Vertical
|
Hand
using for small quantities
Items
such variable efficiency
As
shovel, spatula, etc
Feet
Bowl moist day
Dry
powders or moist crumbs
Dry
powders.
|
Forming
Drying
|
Hand
Mincer
Pelleter
Cooker
extruder
Solar
Mechanical
|
Dough
ball
Moist
noodles
Dry
pellets
Semi-moist/dry
pellets or noodles
Variable
efficiency
Controlled
drying
|
Larval feeds
For
year-round intensive production of fry, there is need to develop artificial
feeds for fry. Some major problems
encountered in feeding artificial diets to clariids include
(i) The
larvae do not readily accept artificial diets;
(ii)
The material used in compounding most fish feeds
compete with conventional human and livestock feeds rendering the finished feed
expensive.
Some
substances e.g. betaine, glycine and Spirulina
have been reported to have flavour-enhancing effects when included in fish diets
(Appelbaum, 1980; Henson, 1990; Hughes, 1991).
Also,
Mgbenka and Orji (1994) reported that ripe, raw, fresh palm oil (FPO) used as
feed attractants improved growth and acceptance of feeds to clariid larvae and
fingerlings but the optimal rate is not yet known. Legendre et al. (1995) made similar report on
growth of Heterobranchus longifilis larvae
fed dietary copra and palm oils.
Food
preference in larval fish has been found to depend on a host of factors
(Dabrowski, 1984; Verreth and Kleyn, 1987). Ingestion of food particles offered to fish is
very strongly influenced by aroma or palatability of the food (Appelbaum, 1980;
Gill, 1989), availability of nutrients present and lipid level of the diet
(Machiels and Van Dam, 1987; Verreth et al. 1987). There is a dearth of information on the use
of local flavours such as ginger, uda,
uziza, etc. as chemattractants or
chemoactivators to improve the acceptance, growth and survival.
Some
non-conventional include such feed ingredients as rumen digesta, sprout
(sorghum malting by-product), mucuna bean seed, devil bean (Igbo, “agbara”), to
mention a few. Mucuna been seed and
sprout, for example, have been reported to contain 28.59% and 26% crude
protein, respectively (Oyenuga, 1968; Okwuosa, 1992). Additionally sprout is rich in the essential
amino acids Lysine and Methionine (Okwuosa, 1992).
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