feed and feeding 25 04

7/28/2019 Feed and Feeding 25 04

1/48

1

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


2/48

2

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


3/48

3

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.


4/48

4

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


5/48

5

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


6/48

6

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)


7/48

7

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


8/48

8

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.


9/48

9

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


10/48

10

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


11/48

11

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


12/48

12

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.


13/48

13

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.


14/48

14

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


15/48

15

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


16/48

16

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


17/48

17

>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)


18/48

18

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)


19/48

19

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


20/48

20

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


21/48

21

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


22/48

22

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


23/48

23

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.


24/48

24

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_niloticus


25/48

25

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


26/48

26

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


27/48

27

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


28/48

28

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


29/48

29

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).
http://www.adb.org/http://www.adb.org/http://www.adb.org/http://www.adb.org/


30/48

30

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


31/48

31

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


32/48

32

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


33/48

33

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


34/48

34

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


35/48

35

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

feed and feeding 25 04

Documents