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Training on improvement of feeding rations for aquaculture development in Gorongosa,
Mozambique, ACP FISH II
Introduction to scientific fish feed nutrition,
detail on Tilapia feed and feeding
Practical applied researches proposals for Gorongosa area
Mr. G. Negroni and Mr. J. Murama
April 2011
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Summary
Foreword
Introduction1 Fish nutritional requirement
2 Ingredients
3 Feed preparation and feeding
4 Feed and genetics
5 Tilapia natural food and feeding habits
6 Tilapia nutritional requirements
7 Tilapia fertilizers and fertilization
8 Tilapia supplemental feeds and feeding
9 Tilapia feed formulation and preparation/production10 Feeding schedules
11 Feeding methods/ methods of feed presentation
12 Nutritional deficiencies
13 Short description of Gorongosa aquaculture situation
14 Applied research proposals
A Green water
B Green water and supplemented local feed
C Separated green water production
15 Conclusions16 Recommendations
Bibliography
Annex I Some indication on plankton and invertebrate nutritive value
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Mature O. Niloticus brood stock
ForewordTilapia is the common name for a vast number of freshwater fishes of the family Cichlid. This is one of
the largest families of fishes, containing more then 1 800 members, some of them in use in aquaculture.
Members of the family range from very small ornamental species used in the aquarium industry to large
food-size species rose in the fish-farming industry. Tilapia culture and production, mainly of food fish,
has been well documented over the years and appears in ancient documents, is drawn on old cave walls,
and is part of the Biblical story. The cichlids, tilapias included, are distributed around the world on both
sides of the equator. However, our interest is in the species originating from Africa and the Middle East.In both more recent history and in Biblical days, tilapia is mentioned as the fish of the miracles or the
fish for the people. Simultaneously and independently, the culture of tilapia as a common and basic
food staple has been developed in various parts of the world. Compared to other cultured species,
tilapia culture and consumption are the most widely spread worldwide. Tilapia is produced and
consumed in over 100 countries and is a staple food for very poor people around the world; however,
nowadays, it has also become a staple cuisine in the most expensive restaurants in luxury markets.
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IntroductionThis paper is to satisfy the ToR requirements to support the IIP in its research for the development of
most efficient, effective and sustainable aquaculture in the area of Gorongosa. The ToR also requested
some more detail as following: to prepare a study identifying needs and initiatives/actions to
providing/improving feed for aquaculture development in Gorongosa.
To develop the above requests, it is necessary to understand some of the basic principles of fish
nutrition and connected researches system organization. Moreover it is necessary to provide
information for efficient, effective and sustainable aquaculture in Gorongosa and particularly for feed
and feeding applied research.
The study it is divided in three main sections:
a general introduction on fish feed nutrition,
a specific section on Tilapia feed and feeding
and a final section providing indication on three possible applied researches to be developed in
Gorongosa.
The applied researches are fitted for the need of Aquaculturist in Gorongosa area and try to
satisfy the need of the local stakeholders represented by 7 aquaculture associations; it is
important be considered that there are not any research facilities in Gorongosa and the area
have some logistic problem. Consideration to have some research facilities in a better organized
area could be discussed.
This study was performed after the first field visit in Gorongosa area that provided first hand
field information with Gorongosa Aquaculture Baseline.
Aquaculture feed system
Even in aquaculture systems where the cultured species derive all their nutrition from natural food, an
understanding of nutritional requirements and how various supplementary feedstuffs (ingredients)
might be utilised can help improve the productivity of the system. For intensive systems, where animals
rely totally on feed inputs, it is essential that feeds are formulated to meet but not exceed the targetspecies energy and nutritional requirements. As many aquaculture farmers in Africa also farm other
livestock (e.g. chickens and pigs), it is worth briefly considering the major differences between feeds for
terrestrial and aquatic species. The major difference is that aquatic animals have much lower
requirements for energy than terrestrial animals; because they are cold-blooded and live in an aquatic
environment, their energy needs for thermoregulation and locomotion are much lower. There are two
obvious implications of this: firstly, aquaculture diets are usually higher in protein; and secondly, the
food conversion efficiency for aquaculture species is usually much better (i.e. the food conversion ratio
(FCR) is lower). Some omnivorous and filter feeding species have some capabilities to utilize alternative
protein sources as there are always competition for protein in nature; in the next chapters we will
analyse as to take advantage of these characteristics for sustainable aquaculture.
1 Fish nutritional requirementsPublished values for aquatic animals protein requirements range from about 2060%. Why is this big
range? The overall protein contents of the tissues of different aquaculture species are actually
remarkably similar at 6070% of dry weight (Anon. 1992) and 1618% of wet weight. The large
difference reflects differences in the ability of different species to utilise non-protein sources, lipid and
carbohydrate, for energy. This is called protein-sparing. For herbivorous and omnivorous species,
dietary protein contents are much lower than for carnivorous species because the animals can use
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carbohydrate (and sometime cellulose) for energy. Although not a nutrient per se, dietary energy is just
as important in fish nutrition as in nutrition for other species. The focus of this paper is on tropical,
freshwater species as Tilapia.
Regardless of whether fish feed predominantly on natural food (including phytoplankton, macro algae,
zooplankton, meio fauna , benthos and other pond organisms, including other fish) or on supplementary
or complete feeds, they require energy and the same suite of nutrients. Research on nutrition of carps,
tilapias and catfish is carried out in Europe and America in addition to Asia (Allan et al. 2000). The most
expensive nutrient to supply is usually protein. Carnivorous species tend to have a higher protein
requirement than omnivores or herbivores, and are more expensive to feed. Earlier life stages such as
fry and fingerlings also require relatively more protein than juveniles and immature adults. Published
requirements for protein and essential amino acids for several species are already well known. Fish do
not require protein as such, but rather a well balanced mix of essential and non-essential amino acids.
One of the nutritional features that separate herbivorous and omnivorous fish from carnivorous fish is
the ability to utilise carbohydrates, especially starch, for energy. Most of the carps, tilapias and many of
the catfish are able to efficiently utilise carbohydrates, a feature that is closely linked with their success
in traditional and extensive and semi-intensive aquaculture where fish are fed on natural food items, or
low-cost, available ingredients that typically contain a high content of carbohydrates.In addition to its role as an energy source, starch also plays a very important role in pellet manufacture.
It is very difficult to process pelleted diets without some carbohydrate (starch), and the matrix formed
by starch is responsible for most of the binding properties of manufactured pellets. The role of starch in
extruded diets is especially critical and largely responsible for buoyancy control. Lipids or fats are
required nutrients for fish and supply energy and essential fatty acids. They can also be an important
consideration in the manufacture of pellets, especially where extrusion technology is used.
Although lipid has a protein-sparing effect for tilapia, contents above 12% depressed growth (reported
in Shiau (2002) some author put at 4% the tilapia requirement, this may be a future research area for
tilapia nutrition (Shiau 2002).
Practical diets for channel catfish typically contain 56% lipid, with about 35% coming from dietary
ingredients and the rest sprayed onto pellets after manufacture, to control dust (Robinson and Li 2002).Channel catfish seem to require n-3 fatty acids (12% of diet) but not n-6 fatty acids (Robinson and Li
2002).
Fish also require vitamins and minerals. In extensive and semi-intensive culture, these requirements are
met through natural food and, in general, supplementary diets require less attention to specific
requirements for vitamins and minerals. Tables 10 and 11 present summaries of published requirements
for vitamins and minerals.
Table N. 1. Dietary protein requirement of carps, tilapias and catfish
Specie Protein diet requirements Size
Carp species
Cyprinus carpio 3038 Fingerling/juveniles
Ctenopharyngodon idella 2835 Fingerling
Hypophthalmichthys molitrix 3742 Fry/fingerling
Aristichthys nobilis 30 Fry
Catla catla 3547 Fry
Tilapias species
Oreochromis niloticus 45 Fry
3036 Fingerlings
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2835 Juveniles
Oreochromis mossambicus 50 Fry
3040 Fingerlings
2935 Juveniles
Catfish
Clarias garinepinus 35Source. from information summarised by Jantrarotai (1996), Takeuchi et al. (2002), Murthy (2002), Shiau
(2002) and Paripatananont (2002).
Table N.2 Quantitative essential amino acid requirements (per cent of dietary protein) Nutritional
requirements of carps, Labeo, catfish and tilapia nilotica
Amino acid Cyprinus carpio Catla catla Labeo rohita O. Niloticus Ictalurus puntatus
Arginine 4,2 4,8 5,8 4,2 4,3
Histidine 2,1 2,5 2,3 1,7 1,5
Isoleucine 2,3 2,4 3,0 3,1 2,6
Leucine 3,4 3,7 4,6 3,4 3,5
Lysine 5,7 6,2 5,6 5,1 5,1Methionine 3,1 3,6 2,9 2,7 2,3
Phenylalanine 6,5 3,7 4,0 3,8 5,0
Threonine 3,9 5,0 4,3 3,8 2,0
Tryptophan 0,8 1,0 1,1 1,0 0,5
Valine 3,6 3,6 3,8 2,8 3,0
Source: Summarized information by NCR (1993), Jantoratoi (1996), Murthy (2002) and Shiau (2002)
Table N.3 Recommended dietary nutrient levels for omnivorous fish species
Nutrient level Fish size class
Fry Fingerlings Juvenile Grower Brood fish
Crude lipid, % minimum 8 7 7 6 5Fish: plant lipid 1:1 1:1 1:1 1;1 1:1
Crude protein, % minim. 42 39 37 35 37
Amino acids, % minimum
Lysine 2.48 2.31 2.19 2.07 2.19
Methionine 0.81 0.75 0.71 0.67 0.71
Cystine 0.29 0.27 0.26 0.24 0.26
Carboydrate, % max 30 35 40 40 40
Major minerals
Calcium, % max 2.5 2.5 2 2 2
Available P, % max 1 0.8 0.8 0.7 0.8
Magnesium, % Min 0.08 0.07 0.07 0.06 0.07Data from Tacon (1990)
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Table N. 4 Vitamin requirements of carps, tilapias and Asian catfish (mg or IU/kg)
Vitamin Cyprinus carpio Orechromis niloticus Clarias batracus
Vitamin A (IU) 4,000 . 20.000
Vitamin D3 Not required
Vitamin E 100-300 50-100
Vitamin K Not requiredThiamine Required Not required
Riblofavin 4-10 Required
Pyridoxine 5.4 Required
Pantothenate 30-50 Required
Nicotinic acid 28 Required
Biotin 1
Folic acid Not required Required
Cynocobalamin Not required Not required
Inositol 440
Choline 4000
Ascorbic acid Not required 1,250 RequiredInformation summarized by Tacon 1990
Table N. 5 Mineral requirements, carps and tilapia
Mineral Carps Tilapias
Calcium 0,028% 0,65%
Phosphorus 0,6 0,7 % 0,5-0,9 %
Magnesium 0,04 0,05 % 0,06-0,08%
Zinc 15-30 mg/Kg 10 mg/Kg
Copper 3 mg/Kg 3-4 mg/Kg
Manganese 12-13 mg/Kg 12 mg/Kg
Information summarized by Tacon (1990) and Jantrartoi (1996)
2 IngredientsProtein, carbohydrate and lipid all supply energy fish need for maintenance and growth. Energy is
released by the oxidation of amino acids, carbohydrates and lipids. However, as there are major
differences between how well different species of fish digest the energy from different ingredients, as
well as major differences between ingredients, it is very important to understand the bioavailability of
energy from different feed ingredients before formulating diets. Comprehensive descriptions of the
pathways of energy flow in fish can be found in NRC (1993) and Tacon (1990).
The major losses from ingested energy occur in faeces (excretory loss). The remainder is called digestible
energy. From digestible energy, losses occur in gill and urine excretions (the remainder is metabolisable
energy). From metabolisable energy, losses occur in energy needed for waste formation and digestionand adsorption (the remainder is net energy). From net energy, any energy not used for maintenance
(basal metabolism, voluntary activity and any thermal regulation), becomes recovered energy and is that
energy contained in the fish carcass (NRC 1993).
In contrast to warm-blooded terrestrial animals, fish are cold blooded, and once excretory losses of
energy are accounted for, the other losses are minimal, and differences between different ingredients
and fish species relatively minor. For this reason, determination of digestible energy is usually the focus
of ingredient evaluation in fish nutrition. When evaluating the potential for any ingredient to be used in
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fish feeds the following factors need to be considered:
1. The nutrient composition of the ingredient. In general, the higher the protein content the more
valuable the ingredient (provided there is no contamination or anti-nutritional factors present).
A summary of some of the key nutrients for some of these ingredients are available (e.g.
Hertrampf and Pascual 2000; Anon. 1992). Consistency of composition is very important as well.
Many animal waste products, like slaughterhouse wastes, can vary widely in composition and
this can present considerable difficulties to diet formulators.
2. Availability and price. Clearly, ingredients that are easily available and relatively cheap are
preferable.
3. Presence and concentration of anti-nutrients. Anti-nutrients are usually found in plant
ingredients and can cause serious problems, ranging from reduced feed intake, food efficiency
and growth, as well as pancreatic hypertrophy, hypoglycaemia, liver damage and other
pathologies (De Silva and Anderson 1995). Fortunately, most anti-nutrients are heat labile and
are easily deactivated by cooking. Some of the major anti-nutrients are described in Table 12.
4. Presence of contamination (e.g. from pesticides, hydrocarbons from fuel or oil or toxins from
fungal contamination [a common problem with peanut meal]) (Table 12).
5. Digestibility and how well energy and nutrients are utilised.
Effects on attractiveness and palatability of feeds are important, in general, aquatic products like fish
meals, and animal meals, tend to make feeds more attractive (i.e. bring animals to the feeds) and
palatable (i.e. make fish want to keep eating the feeds). It is well know that there are some undetected
grow factor in some ingredient as for example the fish meal that provide a superior performance to fish
feed. In other chapters it will be mentioned of vitamins and minerals, including their inter and intra
relations, their activities can greatly influences the diet performances.
3 Feed preparation and feedingDifferent aquaculture intensity system
Types of feed preparation are (see also Figure 2) belonging to the aquaculture intensity:1. Extensive no inputs of fertiliser or feeds, animals are totally dependent on
natural food
2. Semi-intensive fertilisers and/or feeds are added to enhance and complement
natural food respectively
3.Intensive animals are totally dependent on nutritionally complete diets.
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Figure 1 Aquaculture system, schematic representation of the range of aquaculture practices in
relation to inputs.
Source: Modified from De Silva (1993)
Practices that involved flooding fields with water containing larval or juvenile fish, or netting off sections
of natural waterways, and then harvesting fish some time later, are examples of extensive aquaculture.
Adding nutrients is usually done to increase productivity, and over 70% of the total production of finfish
in Asia was semi intensive (Tacon et al. 1995).
The simplest method is to add fertilisers. Tacon (1990), Lin et al. (1997), Knud-Hansen (1998) and
Edwards et al. (2000) discuss how and when to fertilise ponds. The basic goal of fertilisation is to
increase the amount of natural food available for fish. Either organic fertilisers (manures), inorganic
fertilisers (sometimes called chemical fertilisers [e.g. urea, superphosphate]) or a combination of both
are used. The basic nutrients added are nitrogen (N), phosphorus (P) and carbon (C). Other nutrients
may also be required to stimulate phytoplankton growth, including potassium (K), silicon (Si), calcium
(Ca), magnesium (Mg) and chloride (Cl), depending on the nutrient status of pond soil and water (Lin et
al. 1997).
Considerations in choosing the type of fertiliser include availability and cost, fertility of water and soil,
and type, availability and value of the fish to be farmed. For detailed accounts of when liming is required
(how much and what types to add see Boyd 1990, Tacon 1990 or Lin et al. 1997). Many inorganic
fertilisers, particularly P, have low solubility in water. Meanwhile nitrogen is more soluble. The
undissolved portion ends up in the sediment and can be released over time or remain bound to
sediments. The amount of nutrients in some types of fertilisers is presented in Table6 (after Lin et al.
1997).
On same farms, manure could be in short supply and often used on other crops. The relative benefits ofusing manure in fish ponds compared with the benefits of using the manure on corn or other crops need
to be considered in the context of whole-farm income and profit.
For semi-intensive farming systems where supplementary feed is added, farmers may just add feeds
towards the end of the culture cycle as natural food resources become overgrazed, or combine fertiliser
and feed inputs throughout the culture cycle. Edwards et al. (2000) emphasised that supplementary
feeds should complement the limiting nutrients in natural foods. They presented unpublished data
demonstrating the sequential improvements to tilapia production when fish in ponds received fertiliser
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only, fertiliser plus an energy supplement, fertiliser plus an energy and a protein supplement, fertiliser
plus an energy, protein and a P supplement, and fertiliser plus an energy, protein, P and vitamin
supplement. The relative merits of different approaches will be determined by the type of species (or
mix of species) being farmed and the availability and cost of fertilisers and supplementary feed
ingredient and feeds.
TableN. 6 Total amount of nutrients in different types of fertilisers.
Fertiliser Nutrient content
Nitrogen Phosphorus
Urea 45 0
Ammonium nitrate 35 0
Superphosphate 0 10
Triple superphosphate 0 22
Diammonium phosphate (DAP) 18 24
Cattle faeces 1.9 0.6
Cattle urine 9.7 0.1
Pig faeces 2.8 1.4
Pig urine 13.2 0.02
Buffalo faeces 1.2 0.6
Buffalo urine 2.1 0.01
Human faeces 3.8 1.9
Human urine 17.1 1.6
Percentage of dry weight for inorganic fertiliser and faeces, urine as liquid
Fish size at harvest in ponds where only fertilisers have been used is often smaller than in ponds where
supplementary feeds or complete diets have been used. Presumably, this is because larger fish have
difficulty obtaining sufficient nutrition from plankton and other natural food items (Edwards et al. 2000). In general, fish productivity is greatest when they are fed nutritionally complete diets. However,
although excellent diets are widely available, their price is oftenprohibitive. Farmers have the option of
using complete diets for part of the culture cycle only (e.g. just after stocking or in the month before
harvest) or blending the complete diet with other feed ingredient(s) (e.g. rice bran or diets for other
animals like pigs or poultry).
Preparing feed
There are many methods of preparing feeds, ranging from none (unprocessed feed ingredients) to
factory-based, sophisticated manufacture of extruded pellets. Supplementary feeds may just be single
ingredients, e.g. rice bran, or quite sophisticated blends of several ingredients. Complete diets are also
sometimes used as supplementary feeds and fed in addition to other ingredients or only at certainstages of the culture cycle. Some species are not very efficient at consuming feed ingredients delivered
as powder and feed delivered in this form may simply act as an expensive fertiliser. To increase the feed
digestibility it is recommended to grind the ingredients to a little size as possible to increase the
ingredient surface area for better gastric enzyme activity. Moulding the feed into moist balls usually
improves the feeding efficiency.
Another common practice is to process feed ingredient(s) through manual or motorised mincers that
force the mixture through a die to give long strands of feed. These strands may then be sun-dried and
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broken up and delivered to fish.
Artisanal feed production can have several advantages but the diet formula must be balanced to obtain
good growing result, size of ingredient particles must be little for a better binding action and to permit
the mincer to make a good work.
Where several ingredients are used, they should be thoroughly mixed before being put through the
mincer. The process of mixing and mincing can increase the feed efficiency by ensuring that individual
food particles are of a suitable size for effective intake and digestion, and that all ingredients are well
distributed within the mixture. Mincer internal pressure also help for better starch digestibility.
Cooking feed
Feed ingredients and mixtures are often cookedbefore being fed to fish. Cooking has several potential
benefits. Firstly, it is very effective at destroying bacteria that may be contaminating the feed or
ingredients. It also helps preserve the feed if it is to be stored. Cooking also helps to increase the
digestibility of carbohydrate rich ingredients (e.g. broken rice, rice bran and corn bran) by gelatinising
the starch. Finally, because of the gelatinisation of starch, cooking can help to bind the feed together.
Other options for delivering feeds include feeding trays or hanging bags.
Feeding practicesThese have the added advantage of helping farmers to monitor feed consumption. The optimum
number and position of feeding trays or bags will depend on fish species and pond size and dynamics. In
general, feeding trays or bags should be positioned in areas where water quality is best and more trays
or bags are better than fewer trays or bags.
If feeds are to be broadcast, it is best to spread them over as large an area as possible and to avoid the
possibility of uneaten feeds building up and decomposing on the pond bottom. Feeding rates and timing
of delivery are very species dependent.
Commercial feed producer presents a number of feeding schedules for different species, but natural
conditions greatly influence the fish feed behaviour intake. Even where ingredients are unprocessed, the
storage of feeds can be a critical issue.
Feed conservation
Feeds or ingredients that are stored incorrectly can become mouldy, fats in the feeds can become rancid
and unpalatable (or even toxic) and any heat-labile vitamins can be damaged or destroyed. It is
preferable to store feeds or ingredients for as short a time as possible. The most important
considerations when storing feeds are temperature and moisture (humidity). Feed in bags should
always be kept on pallets off the floor and not in contact with walls or the ceiling. Feed sheds should be
well ventilated and every effort should be made to make them vermin proof. Care should be taken not
to store feed or ingredients in plastic bags as these can exacerbate problems with condensation. Insects
can also cause considerable damage to feeds and ingredients and should be excluded.
Mouldy feeds and ingredients should not be fed. Mould growth can reduce the nutritional value of feeds
and ingredients (through enzymatic destruction of lipids, amino acids and vitamins), negatively affect
flavour and appearance and, for some moulds, produce metabolites (called mycotoxins) that can be verytoxic to fish.
Diet formulation
Diet formulation it is not an easy process for all animal species as one ingredient is not enough to satisfy
the diet requirements. The requirements of main cultured fish and crustacean are known and it is
available in literature and in some chapter of this papers. The formulation it is a process where the
appropriate feed ingredients are selected and blended to produce a diet with the required amounts of
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the requested nutrients. The most correct diet is the one that: select various ingredients, in a correct
amounts, with balanced nutritional value, in mixable/pelletable system, is palatable, is easy to store and
use.
The basic information required for feed formulation are:
Nutrient requirement of the specie cultivated;
The feeding habit of the specie ;
Ability of the culture organism to utilize nutrients from various ingredients as well the prepared
diet;
o Nutrient composition of the ingredient
o Digestibility (DE) and metabolisable energy (ME) of the ingredient
o Dietary interaction: vitamin-vitamin, mineral-vitamin, micronutrientdiet composition
inter.
Flavour quality
Local availability, cost of the ingredients;
Expected feed consumption
Feed additives needed
Type of feed processed desired
Many factors need to be considered in fish feed formulation, principally both nutrition and feeding cost
must be taken into account. Feed cost is the highest cost for intensive and some time semi-intensive
aquaculture operational costs. Supplying adequate nutrition for aquaculture species involves the
formulation of diets containing 40 essential nutrients and the proper management of a multitude of
factors relating to the diet quality and intake. In essence, bioavailability of nutrient, diet acceptability
(palatability), feed technology, storage methods and chemical contamination can have profound effects
quality of the diet and the performance of the cultured organism. In Intensive system the diet will
provide all the nutrient (and energy) growing factors meanwhile in the semi-intensive system only a
supplemental nutrition will be required.
Some strategic points for an appropriate formulation must be considered:
Feed formulation must be economic (at least cost)
Linear programming are sued but need to consider the nutritional experiences
Considered seasonal changes in ingredient availability and quality
Protein must be of good quality, palatable, of good&balanced amino acid composition, easily
digestible
Energy intake are highly influenced by the protein, vitamin and mineral diet availability
Good and well preserved ingredient provide high quality food
The nutritional consideration that should be taken into account in a diet formulation are the energy
content and the digestible/metabolisable energy to nutrient ratios, particularly the protein to energyratio.
These are followed by the calculation of the protein content and the amino acids balances, selecting
lipid type, and level to satisfy essential fatty acid and energy requirements and augmentation of
vitamins and minerals. Simple algebraic calculation can support the formulation of simple feed diet
without considering the protein amino acids and fatty acids imbalances, more sophisticated linear
programming software are available as simple excel sheet.
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Feeding strategy
The most-effective feeding strategy will not only depend on the species being cultured but also on the
cost and availability of nutritional inputs (fertilisers, supplementary feed ingredients and feeds and
complete diets) and on the market price of the species cultured. Understanding the best strategy or mix
of strategies for different species, farming systems and in different regions is an important priority to
optimise production. Of equal importance is the need to develop effective methods to empower
farmers, especially low-income farmers, to be able to make these decisions for them.
Feeding strategy is influenced by economics, local condition and technology, normally extension services
help in optimizing the above. For Tilapia farming it is recommended the use of fertilisation for green
water production, particularly for remote and rural areas with low capital availability.
4 Feed and geneticsThe genetic selection of a domesticated specie is important and greatly influence the feed utilization as
for other animals species. Particularly, several organisations have invested substantial resources in the
genetic improvement of Nile tilapia. The Genetically Improved Farmed Tilapia (GIFT) strain developed by
the WorldFish Centre as well as other strains (GET EXCEL, GenoMar ASA and GenoMar Supreme Tilapia)
have a significantly better growth performance than unaltered strains (Asian Development Bank,
2005). Selected Tilpaia strain has a better Feed Conversion Factor than other permitting a feed
conversion optimization and reducing feed costs.
Figure 2 Grow of tilapia fry under different feeding frequencies using 43%proteina (hormone sex
reversal) From Sanches and Hayashi (2001)
Source: Sanches and Hayashi (2001), More often feeding provide better results
In the last decades some strains of Orechromis niloticus were selected with good result to avoid the sex
growing pattern differentiation of the Tilapine species, they are already commercialised to the industry.
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Figure 3 Sex differentiation in Tilapia nilotica
5 Tilapia natural food and feeding habitsEarly juveniles and young fish are omnivorous, feeding mainly on zooplankton and zoo benthos but also
ingest detritus and feed on aufwuchs and phytoplankton.At around 6 cm TL the species becomes almost entirely herbivorous feeding mainly on phytoplankton,
using the mucus trap mechanism and its pharyngeal teeth (Moriarty and Moriarty, 1973).
The pH of the stomach varies with the degree of fullness and when full can be as low as 1.4, such that
lyses of blue-green and green algae and diatoms is facilitated (Moriarty, 1973). Enzymatic digestion
occurs in the intestine where pH increases progressively from 5.5 at the exit of the stomach to 8 near
the anus.
Nile tilapia exhibits a diel feeding pattern. Ingestion occurs during the day and digestion occurs mainly at
night (Trewavas, 1983). The digestive tract of Nile tilapia is at least six times the total length of the fish,
providing abundant surface area for digestion and absorption of nutrients from its mainly plant-based
food sources (Figure 2) (Opuszynski and Shireman, 1995). Ontogenetic dietary shifts of different size
classes of Nile tilapia are presented in Table 7.
TableN. 7 Ontogenetic dietary shift (% of total food intake by volume) of different stages/classes of
Nile Tilapia. O. NiloticusFood type Fry Fingerling Juvenile/adult Juvenile/Adult Adult Adult Any size 1-
55 cm
Algae
Phytoplankton
78 80 37 22 10 63-51
Detritus 22 20 74 23
Invertebrates
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zooplankton
Fish 1 0,6 10,7
Macrophytes 73 2 77 1,3 20,4
Data source: 1Abdel-Tawwab and El-Marakby (2004), 2Talde et al. (2004), 3Weliange and Amarasinghe (2003),
4Getachew and Fernando (1989),
5Petr (1967), 6Njiru et al. (2004);
http://www.aquaculture.org.gy/TilapSeed Production
Approximate indicative weight in gr of different size classes of Nile tilapia:
Fry 0.2 1
Fingerlings 1 10
Juveniles 10 - 25
Adults > 25
Figure 4 Nile Tilapia digestive apparatus, note the little stomach and the long intestine
Stomach with pH
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applicable in a commercial set-up. Even though information on the exact quantitative nutrient
requirements for other life stages of tilapia is lacking, it can be expected that early juvenile fish (0.02-
10.0 g) would require a diet higher in protein, lipids, vitamins and minerals and lower in carbohydrates.
Sub-adult fish (10-25 g) require more energy from lipids and carbohydrates for metabolism and a lower
proportion of protein for growth. Adult fish (>25.0 g) would require even less dietary protein for growth
and can utilize even higher levels of carbohydrates as a source of energy. Comprehensive reviews of
tilapia nutrition are available in various publications including that by Jauncey (2000), Shiau (2002), El-
Sayed (2006) and Lim and Webster (2006).
Nile tilapia requires the same ten essential amino acids as other fin fishes. Protein requirements for
optimum growth are dependent on dietary protein quality/source, fish size or age and the energy
contents of the diets and have been reported to vary from as high as 45-50% for first feeding larvae, 35-
40% for fry and fingerlings (0.02-10 g), 30-35% for juveniles (10.0-25.0 g) to 28-30% for on-growing
(>25.0 g) (Table 2). The best protein digestibility occurs at 25C (Stickney, 1997) and the optimum
dietary protein to energy ratio was estimated in the region of 110 to 120 mg per kcal digestible energy
respectively for fry and fingerling. Tilapia brood fish require about 40-45% protein for optimum
reproduction, spawning efficiency and for larval growth and survival.
The lipid nutrition of farmed tilapia has been reviewed by Ng and Chong (2004). The minimum
requirement of dietary lipids in tilapia diets is 5% but improved growth and protein utilization efficiencyhas been reported for diets with 10-15% lipids (Table 2/3). Both n-3 and n-6 polyunsaturated fatty acids
(PUFA) have been shown to be essential for maximal growth of hybrid tilapia (O. niloticus x O. aureus).
For Nile tilapia the quantitative requirement for n-6 PUFA is around 0.5-1.0% (Table 2). Unlike marine
fish species, tilapia appear not to have a requirement for n-3 highly unsaturated fatty acids (HUFAs) such
as EPA (20:5n-3) and DHA (22:6n-3) and its n-3 fatty acid requirement can be met with linolenic acid
(18:3n-3).
The studies and the practical experience has provided the commercial feed industry some reliable diet
as the one shown in Table 8 from CP group, one of the world leading fish and shrimp feeding group.
Table N. 8 Commercial least-cost formulation for tilapia feeds
Nutrient Limit Pre starter Starter Grower FinisherProtein Min 40 30 25 20
Lipid Min 4 4 4 4
Lysine Min 2.04 1.53 1.28 1.02
Total P Max 1.5 1.5 1.5 1.5
Fibre Max 4 4 4 8
Fish meal Min 15 12 10 8
Source: Chawalit et al. 2003 (CP group)
The major nutrient requirements of cultured tilapia are reasonably well established and are summarized
in the following Tables
Table N. 9 Tilapia protein requirement in freshwater
Life stage Weight (g) Requirement (%)
First feeding larvae 45 50
Fry 0.02 1 40
Fingerlings 1 - 10 35 -40
Juveniles 10 - 25 30 - 35
Adults 25-200 30-32
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>200 28-30
Broodstock 40-45
Table N. 10 Protein requirements of Tilapia at different salinities
Species Salinity (ppt) P. requirements (%)
O. niloticus 0.024 0 30.45 30.4
10 28.0
15 28.0
O. Niloticus X O. Aureus 2.88 32-34 24.0
Table N. 11 Essential Amino Acid requirement (EAA) for Tilapia
% of protein % of diet
Arginine 4.20 1.18
Histidine 1.72 0.48
Isoleucine 3.11 0.87
Leucine 3.39 0.95Lysine 5.12 1.43
Methionine 2.68b 0.75
Phenylalanine 3.75c 1.05
Threonine 3.75 1.05
Tryptophan 1.00 0.28
Valine 1.00 0.78
b In the presence of Cystine at 0.54% of dietary protein. Total sulphur amino acid (Methionine plus
Cystine requirements is 3.21% of the protein
c in the presence of tyrosine at 1.79% . Total aromatic acid (phenylalanine plus tyrosine requirement is
5.54 % of the protein
Table N. 12 Crude lipid, essential fatty acid (EFA) and energy
Crude lip %, min 10-15
Essential fatty acids
18: 2n-6 0.5 1 d
20:4n-6 1 d
18:3n-3
20:5n-3
22-6n-3
Carbohydrate % max e 40
Crude fibre % max 8-10
Protein to energy ration (mg/Kcal) 110 f
120 g
d 1 % 20:4n-6 or 0.51% 18:2n-6
e Dietary utilization of carbohydrate appear to decrease with decrease in fish size
f mg protein for kcal of gross energy (GE)
g mg protein for Kcal of digestible energy (DE)
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Data source Shiau (2002), Fitzsimmons (2005), El-saye (2006), Lim and Webster (2006)
TableN. 13 Summary of dietary nutrient (minerals and vitamins) requirement of Nile tilapia,
Oreochromis niloticus (% of dry feed except otherwise mentioned)
MineralsMacroelements %
Calcium, max 0.7a
Phosphorus, min 0.8-1.0
Magnesium, min 0.06 - 0.08
Potassium 0.21-0.33b
Microelements, min mg/kg dry dietIron 60
Sulphur
Chlorine
Copper 2-3
Manganese 12
Zinc 30-79
Cobalt
Selenium 0.4Iodine 1
Molybdenium
Chromium 139.6 b
Fluorine
Vitamins, min IU/Kg dry diet
Vit A (Retinol) 5,000
Vit D (Cholecalciferol) 375 b
Vitamins , min mg/Kg dry diet
Vitamin E ( - tocopherol) 50-100 c
Vitamin K 4.4
Vitamin B1 (Thiamine) 4
Vitamin B2 (Riboflavin) 5-6 d
Vitamin B3 (Niacin/nicotinic acid) 26 121 b
Vitamin B5 (Pantothenic acid) 10 a
Vitamin B6 (Pyridoxine) 1.7 9.5 e
Vitamin B9 (Folic acid) 0.5
Vitamin B12 (Cyanocobalamin) Not required
Choline 1.000 b
Inositol 400 b
Vitamin B7 (Biotin) 0.06 c
Vitamin C (Ascorbic acid) 420
Minerals macro elements %
a Based on data from O. aureus;
b Based on data from hybrid tilapia (O. niloticus X O. aureus).
c Based on diets with 5% lipid. Vitamin E requirement increases to 500 mg/kg dry diet at 10-15% dietary lipid level
D Based on data from hybrid tilapia (O. mossambicus X O. niloticus) and O. aureus
e Based on data from hybrid tilapia (O. niloticus X O. aureus) at dietary protein level of 28%,
requirement 15-16.5 mg/kg diet at 36% protein diet
Data source: Shiau (2002), Fitzsimmons (2005), El-Sayed (2006), Lim and Webster (2006)
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The exact carbohydrate requirements of tilapia species are not known. Carbohydrates are included in
tilapia feeds to provide a cheap source of energy and for improving pellet binding properties. Tilapia can
efficiently utilize as much as 35-40% digestible carbohydrate. Carbohydrate utilization by tilapia is
affected by a number of factors, including carbohydrate source, other dietary ingredients, fish species
and size and feeding frequency (El-Sayed, 2006). Complex carbohydrates such as starches are better
utilized than disaccharides and monosaccharides by tilapias. Hybrid tilapia (O. niloticus x O. aureus)
showed the carbohydrate (44%) digestibility in the following progression:
starch > maltose > sucrose > lactose > glucose
(Stickney, 1997).
Carbohydrate utilization by tilapia species have been reviewed by Shiau (1997). Nile tilapia are capable
of utilizing high levels of various carbohydrates of between 30 to 70% of the diet. It has also been
demonstrated that larger hybrid tilapia (O. niloticus x O. aureus) utilized carbohydrates better than
smaller sized fish. Stickney (2006) reported that the inclusion of soluble non-starch polysaccharides
(NSP) in the form of cellulose in the diet of Nile tilapia increased the organic loading of the culturesystem, while insoluble NSP (guar gum) placed less organic load on the system by increasing nutrient
digestibility and improving faeces recovery.
Vitamin supplementation is not necessary for tilapia in semi-intensive farming systems, while vitamins
are generally necessary for optimum growth and health of tilapia in intensive culture systems where
limited natural foods are available. Several vitamin requirements of tilapia are known to be affected by
other dietary factors and these must be taken into consideration in diet formulations.
For example, the vitamin E requirement is influenced by dietary lipid level with Nile tilapia requiring 50-
100 mg/kg when fed diets with 5% lipid and increased to 500 mg/kg diet for diets with 10-15% lipid
(Table 3). Apart from dietary lipid level, the unsaturation index of the dietary oil will also affect the
amount of vitamin E required.The presence of other antioxidants in the diet, such as vitamin C, has been reported to spare vitamin E
in diets for hybrid tilapia. Choline can be spared to some extent by betaine. Carotene can be bio-
converted to vitamin A with a conversion ratio of about 19:1 (Hu et al., 2006). Pyridoxine requirement
level has been shown to vary with the level of protein in the diet: 1.7-9.5 and 15-16.5 mg/kg diet for fish
fed 28 and 36% protein diets, respectively for hybrid tilapia.
The source of dietary carbohydrates influences niacin requirement for hybrid tilapia which was reported
to be 121 mg/kg for dextrin-based diets and 26 mg/kg for fish fed glucose-based diets. Vitamin
requirement values are also dependent on the stability and bioavailability of the vitamin compound that
was used. For example, the phosphate forms of ascorbic acid are more available than the sulphate
forms.
There is little information on the mineral requirements of tilapia. Like other aquatic animals, tilapias are
able to absorb minerals from the culture water which makes the quantitative determination of these
elements difficult to carry out. For example, when Nile tilapia reared in fertilized ponds were fed with
diets either containing complete mineral mixes or one deficient in Ca, P, Mg, Na, K, Fe, Zn, Mn or I and it
was found that only the addition of phosphorous significantly affected weight gain, food conversion
ratio and protein efficiency ratio (Stickney, 1997). Despite its ability to absorb minerals from the culture
water and the presence of minerals in feed ingredients, tilapia feeds should contain supplemental
mineral premixes. This is to ensure that sufficient levels are available to protect against mineral
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deficiencies caused by reduced bioavailability such as when plant phosphorus sources are used in tilapia
feeds. Like vitamins, the amount of minerals to be added in the diet will also depend on the source of
the element. For example, Shiau and Su (2003) reported that ferric citrate is only half as effective
compared to ferrous sulphate in meeting the iron requirement of tilapia.
Phytase
Many of the plant-based feed ingredients have high phytic acid content which appears to bind metal
ions such as calcium, phosphorus, magnesium, manganese, zinc and iron rendering them unavailable.
The ability of phytic acid to bind metal ions is lost when the phosphate groups are hydrolyzed through
the action of enzyme phytase. Although phytase activity has been shown to be present in ruminants,
animals with a simple stomach such as fish lack this enzyme in their gastrointestinal tracts and hence
cannot utilize the phytate bound phosphorus or other metal ions. Therefore, feeds are often
supplemented with phosphorus in the form of mono or di-calcium phosphate. Phosphorus and calcium
requirements are interdependent. Addition of microbial phytase in the diet of Nile tilapia significantly
improved the growth of fish (Portz et al., 2003; Furuya et al., 2003). Variations in the quantitative values
reported in literature can also be expected due to differences in dietary ingredients used.
7 Fertilizers and fertilizationIn general, tilapias can efficiently utilize natural food and yields of 2,000 kg per hectare can be sustained
in well-fertilized ponds without any supplemental feed. This feeding strategy depends on the application
of inorganic and/or organic fertilizers to stimulate the production of live food organisms and plants in
the culture system and is typical of extensive and semi-intensive tilapia farming systems. In the case of
Nile tilapia culture, the production of phytoplankton should be the primary target (see Section A above).
The success of a pond fertilization strategy depends on the initial drying, tilling and liming of the pond
substratum (Figure 8). The drying out period to allow for adequate mud mineralization is usually
between 5 to 10 days. After drying, the pond bottom should be limed to reduce acidity/to increase pH
and to ensure that the culture water has a pH of about 7-8. This will allow the tilapia culture ponds to
respond optimally to fertilization. The total alkalinity of the water should be above 20 mg/l. A suggestedliming rate for ponds based on pH and soil texture is given in Table 4.
Table N. 14
Fertilization program
Inorganic fertilizers Organic fertilizers
Pond drying
Removal of excessive mud and silt
Liming
Tilling
Partial filling Manuring
FertilizingProgressive filling
Stocking
Pond fertilization strategies are locality dependent. Many factors determine the success of a fertilization
regimen. The most important of these are soil type, water quality, species cultured and the type,
application method and rate of fertilizers used and all must be carefully considered. Despite the lack of a
standardized protocol of pond fertilization, the effectiveness of any program can be easily monitored by
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measuring the turbidity of the pond water by means of a Secchi disk, on the assumption that the main
source of turbidity within the pond comes from phytoplankton population. It has been recommended
that a Secchi disk visibility of about 30 cm is optimal to achieve and maintain proper fertilization.
The elemental composition of the major organic fertilizers and inorganic fertilizers used in aquaculture is
summarized in the following Tables.
To have some practical points to evaluate the animal manure production
Table N. 14.1 Animal production and pond manuring
Specie Production Kg/dry
manure organic matter /
100 Kg live weight of
animals
Advice on % of manuring
(dry basis) on fish
standing stock
Max animal number
over 1 Ha of pond
Cows / cattle to 1 3 - 4 80 150
Sheep to 1 3 -4 350 - 500
Pig 1 to 1 3 -4 70
Duck 1 to2 2 (2 - 4) 1200 1500
Chick 1 to2 2 (2 3) 800 - 1000
Source: G. Schroeder and Negroni unpublished practical trial
Some practical recommendation for pond manuring:
Recommended manuring: max 75 to 100Kg dry matter per day per Ha standing stock biomass
Manure stockage greatly decrease the mineral content
The best manure composition is 20:1:0,2 N-P-K that is similar to the duck and chicken fresh
manure, C must be available
Look in the early morning if fish are gulping the water surface, this means low oxygen, stop
manuring and add some freshwater
Animals can be hold over the pond as the fresh manure ahs the best composition, and less
manpower is utilized for collection
Utilize 8000 / 20.000 / Ha fish stocking density according the desired size of the final product
Main species profiting of the manuring are: Tilapia, carps and milkfish species
Drain, disinfect and dry the pond before stocking and fertilize before re-stocking
25.000 to 35.000 kg of standing stock /Ha can stay in a well fertilized pond, if we need more fish
we need to supplement with a diet the additional fish weight
30 Kg day/Ha fish weight can be produced in an appropriate fertilized (manured) and managed
pond
Pond develop a deep olive-green or brown-green colour it is OK on the contrary add more
manure or chemical fertilizer
Manuring must be often and uniformly distributed in the pond are to provide a good plankton
development, plankton must be nourished constantly
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Table N. 15 List of commonly used organic manure used for tilapia culture and their N:P ratioand NPK content
Type of fertilizers N:P ratio and Ca and NPK content (%)
N:P Ratio Nitrogen (N) Phosphorous (P) Potassium (K)
Faeces / Dung
Buffalo 2.24 1.23 0.55 0.69Cattle 3.41 1.91 0.56 1.40
Sheep 2.37 1.87 0.79 0.92
Pig 2.06 2.80 1.36 1.18
Poultry manure 1.99 3.77 1.89 1.76
Duck manure 1.90 2.15 1.13 1.15
Urine
Buffalo 205 2.05 0.01 3.78
Cattle 194.80 9.74 0.05 7.78
Sheep 99 9.9 0.10 12.31
Pig 8.70 10.88 1.25 17.86
Meals
Blood meal 16.85 11.12 0.66 -
Bone meal 0.31 3.36 10.81 -
Plant material
Wheat straw 4,45 0,49 0,11 1,06
Maize straw 5,80 0,58 0,10 1,38
Soybean stalk - 1,30
Cotton stalk and leave 5,87 0,88 0,15 1,85
Cottonseed meal 7,83 7,05 0,90 1,16
Groundnut straw - 0,59 - -
Bean straw 4,91 1,57 0,32 1,34
Coffee pulp 14,92 1,79 0,12 1,80
Sugarcane trash 8,75 0,35 0,04 1.50
Grass 13,67 0,41 0,03 0,26
Oil palm pressured fibre 12,40 1,24 0,10 0,36
Molasses 0,39 2,09 5,30 1,99
Aquatic plant and algae
Water Hyacinth 5.51 2.04 0.37 3.40
Azolla sp 18.40 3.68 0.20 0.15
Lemna sp 16.55 3.31 0.20 0.69
Ceratophylum 7.02 3.30 0.47 5.90
Hydrilla sp 9.64 2.70 0.28 2.90
Data source Tacon 1987 b
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Table N. 16 . List of commonly used organic/ inorganic fertilizers, their rate, frequency used for tilapia cultureCountry Fish size Stocking density (N. Ha) Fertilizers Rate (Kg/Ha/Year) Frequency App. Method
Panama On growing Dried pig manure 24.800
Dried poultry
manure
18.200
Dried cattle/goat
manure
36.500
Rwanda Spawners Animal manure 7.800-13.000
Fingerlings 50.000 Animal manure 13.000
Fingerlings 20.000 Dried poultry 14.000
Thailand Growout 10.000 Liquid cesspool
slurry (DM)
27.600-45.400 7/week
Kenya 5.000-20.000 Fresh cow
manure
78.000 235.000 1/week Crib
Semi-dry mixture
of goat, sheep,
poultry, rabbit
droppings
1.456-5.929 1/week Broadcasted
or crib
Fresh pig manure 39.000 1/week Broadcasted
or crib
Fresh rumencontents
26.000-41.600 1/week Broadcasting
Rwanda Fingerlings Single
superphosphate
Urea
480
120 -
Zambia Growout Double
superphosphate
672
Ivory
coast
Growout Triple
superphosphate
720 2/month Suspended
basket
Thailand Fingerling 17.600 Dried poultry
manure
3.900 1/week
Urea 3.068 1/week Dissolved w.
Triple
superphosphate
1.300 1/week Sacking
overnight
Data source: Tacon (1987b); Tacon (1991); Broussard et al. (1983); Knud-Hansen et al.(1991)
The first limiting nutrients affecting phytoplankton productivity in ponds are phosphate (P) and nitrogen
(N). Inorganic fertilizers are commercially available and are generally based primarily on one major
element and the correct combination of fertilizers is needed to optimally stimulate plankton
productivity. As a general rule, three to five times less P than N should be added to culture ponds.
Organic fertilizers or manure include all plant and animal materials and their fertilizer value is
dependent primarily upon its carbon (C), N, P and potassium (K) content. Common organic fertilizers
used in aquaculture are poultry, cow and pig dung but cottonseed meal, rice straw and other
agricultural waste products can also be used.Inorganic fertilizers are usually applied on a weekly or bi-weekly basis. Raising the frequency will lower
the risk of sudden phytoplankton blooms, leading to low DO levels. Fertilizers should be applied to
supply 0.5 1 mg/l of nitrogen1 and 0.1 0.5 mg/l of phosphate2. Newly constructed ponds require
higher initial fertilization rates. Organic fertilizers have to be applied as often as possible and almost
daily. In Israel, manure (as dry organic matter) is applied daily at 2-4% of the fish biomass. Few
parameters have to be carefully monitored and fertilization should be immediately stopped if dissolved
oxygen falls below 4.0 mg/l, pH above 9.0, or water transparency below 25 cm.
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A number of country-specific fertilization guide for tilapia pond culture are summarized in Table 17-18.
Table N. 17 Suggested guideline for liming of pond based on Ph and texture of pond soil
Ph of pond soil Lime requirements (Kg/Ha of CaCO3)
Heavy loams or clays Sandy loam Sand
4 14,320 7,160 4,4754 4,5 10,740 5,370 4,475
4,6-5,0 8,950 4,475 3,580
5,1 5,5 5,370 3,580 1,790
5,6 6,0 3,580 1,790 895
6,1 6,5 1,790 1,790 0
Data source: Tacon (1988)
The fertilization regime used will, among others, depend on the management system (extensive versus
semi-intensive), stocking density (no./ha)/biomass of fish (kg/ha) and type of fertilizers used (organic,
inorganic or combination). Site specific factors other than nutrient input that affects primary
productivity (e.g., weather) makes it difficult to provide a general pond fertilization guide for tilapia
farming. Therefore, the information provided in Table 16/17 is intended purely as a general guideline.
In Thailand, chicken manure applied weekly at 200-250 kg dry weight/ha together with urea and triple
super phosphate (TSP) at 28 kg N and 7 kg P/ha/week, respectively, produced a net harvest of 3.4-4.5
tonnes/ha in 150 days at a stocking density of 3 fish/m2 or an extrapolated net annual yield of 8-11
tonnes/ha. (http://www.fao.org/fishery/culturedspecies/Oreochromis_niloticus).
In Honduras where there is sufficient dissolved phosphorus in the culture water, weekly application of
chicken manure at 750 kg dry matter/ha and urea at 14.1 kg N/ha yielded 3.7 tonnes of tilapia/ha when
stocked at 2 fish/m2. Grow-out tilapia ponds in Indonesia are fertilized with urea, TSP, and manure at
2.5 g/m2/week, 1.25 g/m2/week and 250 kg/month, respectively, together with a feeding regime of
commercial tilapia feeds (Nur, 2007 see next table 18).
Table N. 18 Summary of fertilization practices for Nile tilapia in three different countriesCountry Stocking
density
Chicken manure Urea1 TSP2
Thailand 3 fish/m2 200-250 kg3/ha/week 28.0 kg N/ha/week 7.0 kg P/ha/week
Honduras 2 fish/m2 750 kg3/ha/week 14.1 kg N/ha/week *
Indonesia*** 4-8 fish/m2 250 kg/ha/month 2.5 kg/ha/week 1.25 kg/ha/week
Source: Nur 2007
One of the interesting ways to improve pond productivityis to practice polyculture with common carp or
shrimp. While feeding, common carp stir up the substratum and this releases nutrients into the water
column and therefore enhances primary production. In extensive farming systems in Africa and Asia,
bamboo poles or tree branches are planted within the ponds to increase natural productivity. These
substrates increase the surface area for enhanced periphyton production (see Figure 5), which is grazedby the fish. More recently, synthetic substrates (Aquamats) for bacteria and algae have been used in
tilapia and shrimp culture systems.
Although tilapia is a hardy fish and can tolerate extremes in most water quality variables, they should
not be exposed to low dissolved oxygen for longer period as it negatively affect the metabolism resulting
in reduced growth (Stickney, 1996). Tilapia cannot tolerate water temperature below 12C (Tom Hecht,
Pers. comm.). Pond culture of Nile tilapia with shrimp, leads to improved feed utilization efficiency,
http://www.fao.org/fishery/culturedspecies/Oreochromis_niloticushttp://www.fao.org/fishery/culturedspecies/Oreochromis_niloticushttp://www.fao.org/fishery/culturedspecies/Oreochromis_niloticushttp://www.fao.org/fishery/culturedspecies/Oreochromis_niloticus7/28/2019 Feed and Feeding 25 04
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reducing shrimp pathologies, reduced environmental pollution and improved production (Yi et al., 2003
and Negroni 2011 unpublished data).
Figure 5 Poles in the pond to increase natural periphyton production
8 Supplemental feeds and feedingSupplemental feeding compensates for natural food nutrient deficiencies in fertilized ponds and is the
usual feeding method for semi-intensive tilapia culture systems. A comprehensive review supplemental
feeding practices and of various supplementary feeds is provided by Tacon (1988) and De Silva (1995).
The use of supplemental feeds leads to significant increases in tilapia yield in comparison to fertilized
ponds alone.
However, farmers must be aware of the complex interactions between the natural food supply and
supplemental feeds and those incorrect feeding strategies can lead to financial loss. Supplemental
feeding should be carried out properly coupled with a good understanding of the nutrient content of the
various feed ingredients (Table 19). Supplementary feeds can be made up of single ingredients or
combinations of ingredients either simply mixed together or powdered and compounded into moist
dough before feeding.
The most common feedstuffs are agricultural by-products such as rice bran, broken rice and maize with
occasional use of grass and leaves. Dry ingredients are normally ground before being dispersed
throughout the pond. However, many raw ingredients of plant origin are inappropriate for tilapia fry,
but can be used for fingerling and larger fish. It should be mentioned that commercially formulated
pellets can also be considered as supplementary feed when used in combination with a pond
fertilization regime, or used in combination with cheap feed ingredients. Some farmers often use
formulated feed as a single feed source for a particular life stage
Table N. 19 List of most commonly used supplemental feed ingredient in Tilapia culture, nutrientcontents are given in % on feed basis
Feed
ingredient
Nutrient composition Estimated FCR
Moisture Crude protein Crude lipid Ash Gross energy (Kj/g)
Feeds of animal originBlood meal 10.4 81.5 2 20 1.5 1.7
Chironomidis, fr. 84 9 14 7 7.5 2.3 4.4
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Daphnidis, fresh 89 3 7.5 1.2 2.5 4 6.4
Earthworm 81.1 10.6 2 3 3.1 8-10
Fishmeal 7-9 57 - 72 4 - 9 10 - 26 16 - 20 1.5 - 3
Trash fish 52 - 83 11 - 26 1 - 36 1 2 4 9
Meat meal 6.9 53 31 16.8 2
Silkworm pupae,
fresh
74.9 13.7 8 1.2 6.9 3-5
Snail meat, fresh 78 12 1 4 4 22
Feeds of plant originBanana leaves 75 2.4 1 4.7 25
Cassava leaves 74 7.7 1 2 4.9 10-20
Corn 12.2 9.6 4 2 16.3 4.6
Cottonseed cake 7.8 10.7 22-41 8.3 17 - 18 3
Soybean 9 24-38 10 7 18-21 3-5
Water hyacinth 91.5 0.2 1.3 1 1.4 50
Wheat bran 12 14.7 4 5.5 16 6. - 7
Data source: Tacon (1987, 1988)
There are no generalized feeding tables for the use of supplementary feeds in Nile tilapia farming
although feed manufactures often provide recommended feeding rates for their feeds. However, thereare some general rules. The population of natural food organisms in the culture system gradually
decreases as the standing crop increases such that the amount of supplementary feeds should be
gradually increased as the fish grow. Feeding rates should be assessed according to the natural
productivity of the ponds and the fertilization program.
Thus, if transparency decreases, feeding rates should be reduced. Conversely, if transparency increases,
feeding rates and/or nutrient quality (such as protein content) should be increased. Optimal feeding
rates and frequency of feeding are site specific and also depends on the various types of supplementary
feed items used. In a detailed profitability analyses of various inputs for pond culture of Nile tilapia in
Thailand, Yi and Lin (2000) reported that fertilizing ponds with urea and TSP at 28 kg N and 7 kg
P/ha/week, respectively, and supplementing with pelleted feed at 50% satiation level starting only when
the fish reaches 100 g size, yielded the best economic returns.Orachunwong et al. (2001) reported that red hybrid tilapia in floating cages fed a 25% protein diet three
to four times a day resulted in better growth and feed conversion ratio than when fed twice a day.
9 Tilapia feed formulation and preparation/productionLive food
First feeding Nile tilapia juveniles that do not have access to live food display morphological anomalies in
their digestive system that reduces their ability to digest, absorb and assimilate nutrients efficiently,
resulting in low weight gain that may persist through adulthood (Bishop and Watts, 1998). The use of
live food can therefore reduce the time required to complete organogenesis and the early completion of
a functional digestive system thereby maximizing the growth potential of the tilapia fry.
The practise of rearing juveniles in smaller ponds or in hapas prior to ongrowing is universal. Natural
productivity in nursing ponds or hapas provides the necessary live food for the growth of tilapia. Organic
and/or inorganic fertilizers can be used to stimulate the production of phytoplankton which is the main
live food consumed by tilapia during these early stages.
Therefore, no specialized separate live food production facilities are needed in the culture of tilapia
although there are reports that many tilapia farmers produce zooplankton such as Daphnia and Moina
and use them as supplementary feed for fry and fingerlings for increased production. Also separated
plankton production is under several applied researches with interesting results.
FAO-FIRA Species Profile for Aquaculture Feed and Nutrient Resources Information System: 2011 10
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Formulated feedsHigh quality formulated feeds are used to achieve high yields and large sized fish (600-900 g) within a
short period of time. The maximum size at harvest of Nile tilapia reared in ponds that are only fertilized
is generally less than 250 g after 5 months of on growing.
Under semi-intensive farming systems, most tilapia farmers in Asia fertilize their ponds and use
formulated feeds. However, in intensive pond and tank culture systems or in cages, tilapia farmers
mainly depend on commercial pelleted feeds.
The nutrient inputs used and the yield and weight of tilapia at harvest in several Asian countries are
summarized by Dey (2001). In terms of pond yields, Dey (2001) reported that overall, the average yield
of pond farming in Taiwan, Province of China is very high (12 to 17 tonnes/ha) while ponds in
Bangladesh, China, the Philippines, Thailand and Viet Nam produce around 1.7, 6.6., 3.0, 6.3 and 3.0
tonnes/ha, respectively.
Tacon, Hasan and Subasinghe (2006) conservatively estimated that the global production of industrially
manufactured aquafeeds in 2003 was about 19.5 million tonnes with projections of 27.7 million tonnes
by the year 2010. Tilapia feeds accounted for about 8.1% of global aquafeed production in 2003.
Commercial tilapia feeds are mainly dry sinking pellets and extruded floating pellets.
Production estimates for farm-made tilapia feeds are not available as these are usually site specific anddependent on locally available feed ingredients. In countries such as the Philippines, on-farm feeds are
not very popular as tilapia farmers find it more convenient to purchase formulated feeds from feed
companies. A brief summary of the advantages and disadvantages of various feed types is provided in
Table 9.
The main issue in formulating feed is to meet the protein and essential amino acids (EAAs) requirements
of the species. Fishmeal is generally the preferred protein source because of the high quality of the
protein and its EAA profile. However, fishmeal is generally expensive and is not always available. Nile
tilapia can be fed with a high percentage of plant proteins.
It is economically judicious to replace fishmeal with alternative protein sources including animal by-
products, oilseed meal and cakes, legumes and cereal by-products and aquatic plants. Most of these
ingredients are deficient in some EAA and hence require supplementation or be compensated withother feedstuffs.
Although most of the oilseed cakes/by-products are generally deficient in lysine and methionine,
blending of different oilseed cakes often provides balanced amino acid profile. However they contain
many anti-nutritional factors (such as gossypol, glucosinolates, saponins, trypsin inhibitors etc.) which
limit their use in compound feeds or require removal/inactivation through specific processing (such as
heating, cooking etc). There are also several non-conventional protein sources that may be suitable for
O. niloticus such as silkworm pupae, snails, earthworms, Spirulina, corn and wheat gluten, almond cake,
sesame cake, brewery waste, etc.
10 Tilapia feed ingredients
Feed ingredients of plant and animal origin used in the formulation of tilapia feeds with their generalnutritional values, Tilapia nutritional requirements and other relevant information are provided in
Tables 10-11-12-20. The maximum inclusion level of each feedstuff that can be used in tilapia feeds is
dependent on several factors such as the level of dietary protein, how the feedstuff was processed, life
stage of the fish, economics, availability, etc.
Some practical application for their maximum dietary inclusion based on the data obtained from tilapia
and other herbivorous fishes are already included in several practical diet. However, it should be noted
that these are only suggestions and with research data coming from more recent feeding trials and the
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advancement of processing techniques, many of these recommendations would need to be revised in
future.
Better processing techniques of feedstuffs such as soybean meal and poultry by-product meal can now
be included at much higher levels in tilapia feeds than previously recommended. A review of various
alternative dietary protein sources for farmed tilapia and its replacement potential for fishmeal in tilapia
diets is provided by El-Sayed (2006). A summary of the tested and recommended levels of different
protein sources for Nile tilapia compiled by El-Sayed (2006) is listed in Table 20
Table N. 20 Recommended levels of different alternative protein sources tested for Nile Tilapia under
laboratory conditions. Level tested is a replacement of conventional protein sources as fishmeal or
soybean meal
Protein source Level tested % Recommended level % Fish weightAnimal origin
Shrimp meal 100 100 20
Shrimp head waste 0-60 60 1.4
Meat and bone meal + Met 40-50 50 11 mg
Meat and bone meal 100 100 20
Blood meal 100
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Moist
No energy
requirement
(pellets may be
made by hand with
a meat mincer and
then sun dried);
vitamins preserved.
Feeds available onsite. Easy to make.
Utilize local waste
products. Dry feed
last longer than
moist feeds.
Starches not
cooked and not well
digestible; low
water stability
(additional binder
may be
required);shorter
storage period; lowFCRs; large surface
required for drying.
Moist feed cannot
be stored and need
to be used
immediately.
Hand made dough
Industry manufactured pellet
Sinking
Starches partially
cooked; good
digestibility and
water stability
(gelatinization
improved by prior
steam treatment).
Cheaper than
floating pellets and
so lower capital
costs.
Dry ingredients
required; vitamins
partially lost.
Generally lower FCR
than floating pellet.
Fish feeding can not
be observed.
10% Compressed pellet
Steam treated
compressed pellet
Floating
Almost complete
starch
gelatinization;
better digestibility
and stability; better
FCR; many anti-
nutritional factors
removed with the
heat treatment.
Fish feeding can be
observed.
Extruders more
expensive and so
high production
cost. Requires more
skill in production.
10% Extruded expanded
pellet
Ingredient for Feed formulation
The ingredients used in the formulation of farm-made tilapia feeds vary regionally. In Thailand, a typical
feed formulation for herbivorous fish may include fishmeal (16%), peanut meal (24%), soybean meal
(14%), rice bran (30%), broken rice (15%) and vitamin/mineral premixes (1%) (Somsueb, 1995). Some
examples of farm-made feed formulations for tilapia at various life stages under semi-intensive farming
conditions are listed. In some countries (e.g. the Philippines) farm made feeds are not commonly used,
despite the fact that feed accounts for up to 79% of total operating costs.
The main reason why farm made feeds are not commonly used in the Philippines and in other countries
is because of erratic supplies of raw materials, high capital requirements and the lack of equipment
specifically designed for small scale farmers (www.adb.org).
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Table N. 22 Feed formulae (ingredient composition) and proximate composition of commonly used
farm-made feed (as fed basis) for different life stage of Nile Tilapia in semi-intensive farming system
(Thailand)Ingredient/proximate composition Life stages/size class
Ingredient composition (%)
Early fry Fingerling Grower (cage) Grower (pond)
Cassava starch 15 0 0 0Cassava meal 0 23 23 22
Coconut meal 0 0 0 30
Rice bran 30 15 20 0
Soybean meal 0 30 25 25
Fish meal 47 25 25 20
Fish oil 5 4 4 0
Dicalcium phosphate 1 1 1 1
Vitamin and mineral premix* 2 2 2 2
Proximate composition
Dry matter 8.3 9 9 9.1
Crude protein 30 31 30 29.9
Crude lipid 10 7.4 7.5 4.1
Ash 16.3 12.6 12.8 10.7Crude fibre 3.8 4.2 4.4 6
NFE 31.6 35.8
Gross Energy (Kcal/Kg feed) 2.800 2.700 2.700 2.500
Cost USD/Kg 0.45 0.34 0.32 0.26
Data source: Thongrod (2007)
11 Feeding schedulesIn the provinces of Guangdong, Fujian, Guangxi and Hainan in China, tilapia are stocked at 30,000-
37,500 fish/ha and fed with pelleted feed (28-35% CP) two to three times daily at 6-10% body weight
(BW)/day for fish
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Table N. 23 Composition of mineral premix used in formulated diet for intensive aquaculture
Minerals In freshwater (g/Kg premix) In seawater (g/Kg premix)
CaHP042H2O 727.78
MgSO47H2O 127.5 510
NaCl 60 200
KCl 50 151.11FeSO47H2O 25 100
ZnSO47H2O 5.5 22
MnSO4H2O 2.54 10.5
CuSO47H2O 0.785 3.14
CoSO47H2O 0.4775 1.91
Ca(IO3)6H2O 0.2995 1.18
CrCl36H2O 0.1275 0.51
Data source: Jauncey and Ross (1982)
Table N. 24 Recommended feeding schedules for tilapia provided by feed manufactures, Philippine
Feed type Fish size g Feeding rate (% ofbiomass per day) Growth rate(g/day) Feeding duration(weeks)
B-MEG Tilapia
Fry mash 0.01-2.0 15/20 0.02
Starter crumble 2-15 7/10 0.35
Starter pellet 16-37 6-7 0.47
Grower pellet 38-83 4.4-5.8 0.86
Finisher pellet 91-1.000 1.5-4.1 1.8
Vitarich
Fry mash 3-15 6-13 1-3
Fry crumble 22-62 5-6 4-7
Extr. juvenile pellet 77-105 3-4 8-9Extruded adult p.t. 130-250 2-3 10-14
Data source: Sumagaysay-Chavoso (2007)
TableN. 25 Feeding table for tilapia using formulated feed under semi-intensive farming in pond
Life stage Fish size (g) Stocking
density (N.
Ha)
Feed type Feed size
(mm)
Feeding rate (%
body weight)
Feeding
frequency
(n. /day)
Early fry 0-1 10.000
30.000
Powder 0.2 1 15-10 4
Fry 1-5 Crumble 1 1.5 10-5 2
Fingerling 5-20 Sinking
pellets, balls
1.5 2 5-3
Juvenile 20-100 < 10.000 2 3-2 1-2
Grower >100 3 4 2
Brood stock 150-300 4
Secchi disk depth in fertilized ponds under semi-intensive farming system should be between 25-35 cm
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12 Feeding methods/ methods of feed presentationIn general, the feeding method used for tilapia farming depends on the culture system used, the size of
the farm/ponds and the availability and cost of manual labour. In most tilapia farms where pelleted dry
or moist feeds are used (either farm-made or commercial feeds), broadcasting by hand is the preferred
method of feeding. Being active swimmers, tilapia will readily swim to the edge of the pond or cage
where the feed is being broadcasted.Broadcasting is also the recommended method since this allows the farmer to monitor the feeding
behaviour and general health of the fish with any kind of aquaculture. However, in very large ponds, a
truck may be used to tow a feeder that blows pelleted feeds over a wider area of the pond to ensure
even feed distribution. In our specific case the broadcasting of the feed by hand it is considered
important to manage the little size tanks of the Gorongosa area.
Nevertheless, in some cases where the supplementary feeds are in powder form or other physical forms
that does not allow broadcasting to be carried out effectively, feeding trays, bags or baskets can be
placed in the water to contain these raw materials for the tilapia to consume. In cage culture, feeding
rings are required if floating pellets are used, and feeding trays may be necessary with sinking pellets to
avoid the feed being swept away.
Intensive culture systems are common in countries where the labour cost is high. Various semi-
automatic systems are therefore used to reduce this cost, and increase the growth rate and to reduce
the FCR:
- Clockwork-driven belt feeders permit a constant distribution of feed in small quantities over a 12 hours
period and are very effective for rearing of fry and fingerlings. Vibratory feeders permit to control
feeding rates and times but require power supply.
- Pendulum demand feeders are commonly used for on growing tilapia in cages, raceways and ponds.
They are relatively inexpensive and do not require electrical power. This kind of device still requires feed
allowance monitoring and computing, and may be used together with hand broadcasting. Any dry pellet
can be used but extruded floating pellets are recommended because they reduce the risk of clogging the
feeder through the disintegration of pellets from water splashing.
- Electrical systems such as scatter feeders can spread pellets over the pond surface and allow for strict
control of feeding rates.
In super-intensive systems, computer controlled automatic feeders are used. A distribution network is
installed throughout the fish farm and the feed is send from the silos to the fish with an air-compressor.
No handling is required and the feeding rates and frequencies are managed from a computer. This
equipment is often used in closed recirculation fish farms where feeding may be accurately adjusted
with the supply of oxygen to the system. The use of demand feeder can complement manual hand
feeding of the fish. Automatic feeders can also be set to dispense larval feeds continuously to allow
tilapia fry access to feeds throughout the day. Feeding hours should also be constant in order to adjustthe fish behaviour. The author prefers hand feeding for the easy monitoring of the aquatic animal
behaviour.
13 Nutritional deficienciesIt is important for farmers to recognise at least the most common nutritive deficiency symptoms.
Deficiency signs of farmed tilapia may occur when fish are fed nutrient deficient diets or raised in a low
nutrient-input culture system. Essential amino acid (EAA) deficiency in tilapia generally leads to loss of
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appetite, retarded growth, and poor feed utilization efficiency (Table 30, EAA/EFA). In some fish species
(e.g. rainbow trout, sockeye salmon, Atlantic salmon, chum salmon, coho salmon), lysine, methionine or
tryptophan deficiency results in various signs such as scoliosis, lordosis, fin erosions and cataracts
although none of these deficiency signs have been reported for tilapias.
Similar to EAA deficiency, the lack of essential fatty acids (EFA) will also lead to loss of appetite and poor
growth in tilapia. Other reported signs of EFA deficiencies in Nile tilapia include swollen pale and fatty
livers.
Mineral deficiencies are difficult assess in tilapia as most trace elements are obtained both from the
dietary ingredients and from the culture water. The following deficiency signs have been reported for
Nile tilapia:
- calcium- reduced growth, poor feed conversion and bone mineralization;
- magnesium- whole-body hypercalcinosis;
- and manganese- reduced growth and skeletal abnormalities.
In a study by Dabrowska et al. (1989) with Nile tilapia, excess magnesium (0.32%) in a low-protein (24%)
diet produced severe growth retardation and showed a significant decrease in blood parameters,
haematocrit and haemoglobin content, and magnesium deficiency in a high-protein (44%) diet caused
whole-body hypercalcinosis. A dietary magnesium content of 0.059-0.077% was adequate for optimum
performance of this species.Vitamin deficiency symptoms of tilapia under controlled culture conditions have been extensively
reviewed by Jauncey (2000), El-Sayed (2006) and Lim and Webster (2006) and these are summarized in
the next table. It should be noted that under culture conditions, vitamin deficiency signs are not a
common occurrence in tilapia. In fact, several studies have reported on the non-essentiality of adding
vitamin premixes to tilapia diets (for review, see Jauncey, 2000).
Vitamins obtained from natural food in fertilized ponds, endogenous vitamins present in feed
ingredients used in tilapia feeds and the microbial biosynthesis of some vitamins in the gut are all likely
to contribute significantly to the vitamin requirements of tilapia. Ascorbic acid deficiency is common in
intensively cultured fish. This is often due to manufacture error or to improper storage. Indeed, vitamin
C is degraded at high temperatures and after long term storage. Moreover it is rapidly consumed when
the fish are stressed.Vitamin E deficiencies cause anorexia, reduced growth and death. It is also a strong antioxidant that
protects unsaturated fatty acids. Vitamin E deficiency may also lead to pathological effects as a
consequence of oxidized lipids (congestion, haemorrhages, lordosis, exophthalmia etc.) Incorporation of
antibiotics into the feed reduces the vitamin synthesizing capacity of fish. For instance, vitamin B12 is
entirely produced by Nile tilapia in normal conditions but should be added to the feed when fish receive
antibiotic treatments.
TableN. 26 Dietary nutritional deficiency, vitaminsVitamins Species Deficiency signs/syndrome
Vitamin B2 (Riboflavina) O. aureus Poor grow. High mortality, lethargy, fin
erosion, anorexia, loss of body colour,
dwarfism, cataractsVitamin B5 (Pantothetic acid) O. aureus Poor grow, gill lamellae hyperplasia, fin
erosion, haemorrhage, anaemia,
sluggishness
Vitamin B3 (Niacin/Niacotricin acid) Hybrid Tilapia (O. Niloticus X O.
Aureus)
Haemorrhage, deformed snout, gill
oedema and skin, fin and mouth lesions
Vitamin B1 (Thiamin( Hybrid Tilapia Poor grow and poor feed efficiency,
anorexia, light coloration, nervous
disorder, low haematocrit and red blood
cell count and increase serum pyruvate
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Vitamin B6 (Pyridoxine) Hybrid Tilapia Poor grow and poor feed efficiency ,
high mortality, abnormal neurological
signs, anorexia, convulsion caudal fin
erosion, mouth lesion
Vitamin B7(Biotine) Hybrid tilapia Poor grow
Folic acid O. niloticus Poor grow and reduced feed intake and
efficiency
Vitamin B2 (Riboflavin) O. niloticus -
Choline Hybrid tilapia Poor grow and survival, and reduced
blood trygliceride, cholesterol and
phospholipide concentration
Inositol O. niloticus -
Vitamin C (Ascorbic acid) O. niloticus Poor grow and poor feed efficiency,
scoliosis, lordosis, poor wund healing,
haemorrhage, fin erosion, anaemia,
exophthalmia, gill and operculum
deformity
Vitamin A (Retinol) O. niloticus Poor grow and poor feed efficiency,
restneless, abnormal swimming,
blindness, exophthalmia, skin fin and
eye haemorrhage, pot belly syndrome,reduced mucus excretion, high mortality
Vitamin D (Cholecalciferol) Hybrid tilapia Poor grow and poor feed efficiency, low
haemoglobin, reduced liver size
Vitamin K O. niloticus -
Vitamin E (tocopherol) O. niloticus, Poor grow and poor feed efficiency
anorexia, skin and fin haemorrhagic,
muscle degeneration, depigmentation
Data source: Jaucey (2000), El-sayed (2006), Lima nd Webster (2006)
Table N. 27 Dietary nutritional deficiency, essential amino acid (EAA), fatty acid (EFA) and minerals
Essential amino acid Deficiency signs/syndrome
Lysine Dorsal/caudal fin erosion, retard growth, increased mortality
Methionine Retarded growth, cataractTryptophan Retarded growth, scoliosis, lordosis, caudal fin erosion
Essential fatty acid* Retarded growth, swollen pale liver, fatty liver
*reported EFA deficiency signs for O. Niloticus, other general EAA deficiency symptoms in fish
Data source: Tacon (1987, 1992)
Minerals Deficiency signs/syndrome
Phosphorus Lordosis, poor growth
Calcium Reduced growth, poor feed conversion and bone mineralization*
Potassium Reduced grow and feed efficiency, anorexia, convulsions
Magnesium Reduced growth/whole body hypercalcinosis*
Iron Microcytic, homochronic anaemiaZinc Reduce growth and appetite, cataracts, high mortality, erosion of fin and skin
Manganese Reduced growth and skeletal abnormalities*, anorexia, loss of equilibrium
Copper Reduced growth , cataracts
Selenium Increased mortality, muscular dystrophy, reduced growth, cataracts, anaemia
Iodine Thyroid hyperplasia (goitre)
*In italicus, Reported deficiency signs for O. Niloticus, other: general mineral deficiency in fish
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Data source: Chow and Schell (1980), Tacon (1987a), Tacon 1992, NRC 1993, Jaucey 2000
14 Short description of Gorongosa aquacultureGorongosa area was studied under the Gorongosa Aquaculture Baseline from ACP Fish II team in
March 2011, the multi-specialized team had some conclusion visiting 4 of the 7 Aquaculture association
in the Gorongosa district. During the Aquaculture Baseline Study was noted that the GorongosaAquaculturist feed and fertilize too little or too much the ponds they manage lacking an appropriate
system of feeding and ferilization. The average pond is of 100 sq mt of area and the majority of the
farmers own one or two tanks at family level.
The main constrains belong from the scarce control of feed and feeding, particularly the low protein
level of the supplemental feed provided to the ponds. About the green water production and
manage
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