1. POWER RANGER NOTES Fish nutritionand feedtechnology
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Unit 1- Fundamentals of fish nutrition
1.1.Fundamentals of fish nutrition
Good nutrition is of paramount importance for economic production of healthy and high quality product. In
fish farming, nutrition of fish is critical because feed represents 40-50% of the production costs. Fish
nutrition research has advanced in recent years with the development of commercial diets that promote
fish growth and health. Development of species-specific feed formulations support the aquaculture (fish
farming) industry as it expands to satisfy increasing demand for affordable, safe, and high-quality fish and
seafood products.
Culturing fish in captivity, nothing is more important than sound nutrition and adequate feeding. Hence
growth is affected either due to less intake of feed or under utilization of feeds. An undernourished animal
cannot maintain its health and be productive, regardless of the quality of its environment.
The production of nutritionally balanced feed for fish requires efforts in research, quality control, and
biological evaluation. Faulty nutrition obviously impairs fish productivity and result in a deterioration of
health until recognizable diseases ensues. The borderlines between reduced growth and diminished
health, on the one hand, and overt disease, on the other, are very difficult to define. However, the
problem of recognizing a deterioration of performance in its initial stages and taking corrective action will
remain an essential part of the skill of the fish culturist.
Fish feed technology is one of the least developed sectors of aquaculture, particularly in the third world
countries. Most of the present-day information on fish feed is based on nutritional and diet development
work carried out on temperate fish species of fish in advanced countries. Commercial formulations of
feeds are generally proprietary secrets, and the ingredients used are often too expensive to be used in
developing countries. The need for developing suitable feeds based on locally available inexpensive
ingredients has therefore, been widely recognized.
Unit 2- Nutrients and growth
2.1.Nutrients and growth
The fish growth involves laying down of muscle, fat, epithelial and connective tissue. The growth in fish
follows s-shaped curve. Initially, the fish growth will be slow due to the small size of fish and thus the
difficulty in consuming more food. This phase is termed as preparatory phase. With the advancement of
time fish starts to consume more food, grow bigger and their capacity to feed and grow increases.
Beyond certain point, the rate of increase in growth begins to slow down as the total weight of fish has
now increased to a maximum point and thus the growth now occurs at a diminishing rate. Although fish
never stops growing but the growth is slower in older fish and proportional increase in size is greatest in
younger fish.
Like any other terrestrial animal, fish also needs the same nutrients for their growth. However, the amount
of these nutrients varies due to variation of metabolic rate. Hence supply of these nutrients is warranted in
fish feed. Unlike animals, the availability of these nutrients to fish is different due to their surrounding
environment. Some nutrients are available form water, which needs to be considered critically while
formulating feed for fish.
Finfish require around 40 nutrients for optimal growth and well being. The proteins, lipids/fats and
carbohydrates are considered as “macro nutrients”, while vitamins and minerals put together constitute
“micronutrients” required for the healthy growth in fish.

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Unit 8 - Energy
8.1.Introduction
Energy is defined as the capacity to do work, and is derived through the catabolism of dietary
carbohydrates, lipid and protein within the body. Energy is therefore essential for the maintenance of life
processes such as cellular metabolism, growth, reproduction, and physical activity.
8.2.Laws of thermodynamics
All forms of energy are inter-convertible and obey the laws of thermodynamics. The first law of
thermodynamics states that energy may be transformed from one form into another, but can never be
created or destroyed. For example, solar energy can be transformed into heat energy or into plant-food
energy (chemical energy). During this transformation no energy is lost or destroyed. The second law of
thermodynamics states that no transformation of energy will occur unless energy is degraded from a
concentrated form to a less concentrated or more dispersed form, and further that no transformation is
100% efficient. All biological systems follow this law during the conversion of solar energy (a high energy
form) into chemical energy during photosynthesis; a part of the energy transformed from solar to chemical
energy being dissipated as heat energy into the surrounding environment.
8.3.Energy units
Energy is usually expressed in terms of heat units, since all forms of energy are convertible into heat
energy. The basic heat unit normally used is the calorie. One calorie is defined as the amount of heat
required to raise the temperature of one gram of water by one degree centigrade. Since for many
purposes the calorie (cal) is too small a unit of measurement, the kilocalorie (kcal) is often used; 1 kcal =
1000 cal. In many scientific studies the calorie is now being replaced by the joule (J) as the unit of energy;
4.184 J = 1 cal.
8.4.Forms of energy partitioning
 Gross energy (E) is the energy that is released as heat when a substance is completely oxized to carbon
dioxide, nitrous oxide or water.
 Intake energy (IE) is gross energy consumed by an animal in its food. The majority of intake energy is in
the form carbohydrate,protein or lipid.
 Faecal energy (FE) is the gross energy of the faeces. Faeces consists ofundigested food and metabolic
products,which may include sloughed gut epithelial cells, digestive enzymes and secretory products.
 Digeted energy (DE) refers to apparently digested energy with in a food and is determined as the energy in
food minus the energy in faeces (DE=IE-FE).
 Urinary energy (UE) is gross totalenergy in urinary products.
 Gill excretion energy (ZE) is the gross energy of the compounds excreted through the gills.
 Surface energy (SE) is the energy lost from the surface of fish i.e. mucus or scales sloughed off from the
fish.
 Metabolizable energy (ME) is the energy in the food minus the energy lost in faeces, urine and through gill
excretion {ME=IE-(FE+UE+ZE)}. It is energy available for the conduct of the metabolic processes.
 Total heat production energy (HE) is the energy lost from the animal in the form of heat. The heat is
produced as a result of metabolism and so HE is a measure of metabolic rate in fish.
 8.5.Energy metabolism
 Energy metabolism is concerned with the catabolism and oxidation of carbohydrates, lipids and
proteins within the body, and the consequent release and use of the liberated energy as work for

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the maintenance of the life process. The free energy liberated from the catabolism and oxidation
of the major food nutrients is not utilized directly, but rather is trapped in the chemical form of the
energy-rich phosphorus bond of adenosine triphosphate (ATP) and thus ATP is the principal
driving force in the energy-requiring biochemical processes of life.
Fish and shrimp are aquatic ectotherms and so do not have to expend energy in maintaining a
body temperature well above ambient at 37°C. Fish and shrimp therefore have much lower
maintenance of energy requirements than terrestrial farm animals.
Unit 10 - Methods of feed formulation and manufacturing
10.1.Introduction
Feed formulation is essentially applied nutrition. A number of terms and expressions are
introduced that will be put to practical use as information is presented on the nature and
qualities of various feedstuffs and the information presented on the nutrient
requirements of fish. Precise understanding of these terms is essential to their correct
application. One must recognize that some of these terms have a built-in error that
cannot be escaped. This does not eliminate their usefulness in feed formulation.
However, one must appreciate the fact that some are useful approximations of the
values and not true values.
10.2.Steps in feed formulation
The first step in diet formulation is balancing the crude protein and energy levels. This
can be accomplished by trial and error, by the square method for either crude protein
level or energy level and then adjusting, or by solving simultaneous equations. At first, it
is helpful to use at least three feeds tuffs during the initial balancing of protein and
energy levels: one high in protein and high in ME, one low or intermediate in protein and
high in ME, and one low or intermediate in both protein and ME. Once practice makes
one more proficient at diet formulation any number of feedstuffs can be used. One must
remember to reserve room in the formulation for any feed additive, such as a vitamin or
mineral pre-mix.
The second step in diet formulation is to check the levels of indispensable amino acids
in the formulation to be sure the dietary levels meet the requirements of the animal to be
fed. The requirements of fish for indispensable amino acids is expressed as the dietary
level (as a percent of the diet) or as a percent of the dietary protein level. To convert an
amino acid level from the percent of diet to percent of protein, divide the dietary level of
each amino acid by the dietary protein level. It might be of interest to calculate the
dietary levels of all of the indispensable amino acids, but it is not practical to do it all of
the time. If the levels of arginine, lysine, methionine, and tryptophan meet the dietary
requirements of the fish to be fed, the levels of the other six indispensable amino acids
will most likely be above required levels. When using unconventional protein
supplements, the levels of all ten indispensable amino acids should be checked.

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If the diet formulation is low in any amino acid, a feedstuff that contains high levels of
that amino acid must be added to the diet at the expense of another ingredient. Once
the amino acid requirements are met, the dietary protein and energy levels must be
rechecked to, see if any substitution of ingredients has imbalanced the formulation.
In practical feed formulation, pellet quality and acceptability must be considered in
addition to nutrient levels and cost. These considerations will vary from species to
species and with the type of pellet being made.
10.3.Methods of feedformulation
10.3.1.Pearson square method
In most fish diets, protein is the most expensive portion and is usually the first nutrient that is
computed in diet formulation. The energy level of the diet is then adjusted to the desired level by
addition of high energy supplements which are less expensive than protein supplements.
The Pearson square method is an easy way to determine the probable ratios of mixing different
protein ingredient and to formulate a feed with desired dietary protein level.
For example, consider rice bran (with 8.2% protein) and soybean meal (with 44% protein) were
available as feedstuffs to prepare a diet for carp with 27% protein, a square is constructed and the
two feedstuffs with their protein values are put on the two left corners along with the protein
content of each ingredient.
The desired protein level (27%) of the feed is placed in the middle of the square. Next, the
protein level of the feed is subtracted from that of the feedstuffs, placing the answer in the
opposite corner from the feedstuff. Ignore positive or negative signs.
Thus to make the 27 percent crude protein of carp feed, we must mix 17/35.8 of rice bran and
18.8/35.8 soybean meal.
Now, we have to calculate the proportion of mixing the ingredients by weight in relation to their
protein content. This could be elucidated as given below.

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That is, for the preparation of 100 kg of fish feed with 27 percent protein, 47.50 kg of rice bran
and 52.50 kg of soybean meal are to be mixed.
If more than two feedstuffs are used in a feed, they may be grouped into basal feeds (CP < 20
percent) and protein supplements (CP > 20 percent), averaged within each group, and plugged
into the square method. For example, suppose shrimp meal and corn were also available for the
carp feed mentioned above. The crude protein levels of the shrimp meal (52.7 percent) and of
corn (10.2 percent) are averaged with soybean meal and rice bran, respectively.
Basal feed = (21.35/39.15) x 100 = 54.53%
Protein supplement = (17.8/39.15) x 100 = 45.47%
Thus, to make 100 kg of this feed one would mix the following:
Rice bran 27.265 kg
10.3.2.Linear Programming
The mathematical technique available to nutritionists for selecting the best combination of feed
ingredients, to formulate diets at the least possible cost is linear programming. The following
information is necessary for feed formulation using linear programming
 Nutrient content and DE or ME of ingredients;
 Unit price of feedstuffs including vitamin and mineral mixtures;
 Any other additives to be used in the feed
 Minimum and maximum restriction on the amounts of each ingredient in the feed
Least-cost linear programming software for diet formulation is readily available and the cost
varies with the sophistication. A simple Lotus 1-2-3 spread sheet can also be utilized for
formulating feeds, incorporating a smaller number of variables. It should be noted that least-cost
feed formulation is not always practical for small scale aquaculturists using on-farm feed
manufacture facilities where the choice of ingredients available is limited.
10.3.3.Quadratic programming
Nutrient requirements used in linear programming feed formulation are usually fixed for
maximum rate of growth. This may not be the best decision from economic point of view.
Nutrient constraints may be relaxed to bring down feed cost while still achieving acceptable

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lower growth.
Quadratic programming takes into account the growth response within a range of nutrient
constraint. Therefore, good understandings of biological response functions from actual feeding
trials are essential in the use of quadratic programming. For example, inclusion level of arginine
could be reduced by 20% with only a 5% likely reduction of growth of Nile tilapia. Thus high cost
towards arginine supplement can brought down by hardly loosing likely growth of 5% in the
fish.
10.4.Feed Manufacturing
10.4.1.Introduction
The technology of feed processing has undergone substantial improvement in recent years. It
was only sixty years ago that feeds tuffs were mixed on the warehouse floor by the use of a
shovel. Feed processing has progressed from the simple mixing of several ingredients by hand
to mechanical mixing, to continuous mixing, and now to computer controlled mixing and
pelleting. However, the basic concept of mixing ingredients together to result in a nutritionally
balanced feed, has remained unchanged.
To accomplish the mixing of different ingredients, grinding these ingredients to similar particle
sizes, and then putting them together in a single unit, requires a considerable amount of
specialized equipment and technical expertise. Some feed plants are designed for specific
functions, such as making poultry feeds exclusively; others are designed for producing a variety
of feeds.
10.4.2.Receiving
The first operation in the feed processing plant involves the receiving of raw materials
into the plant premises. Feed ingredients arrive in sacks, or other small containers, and
in bulk.
10.4.3.Processing
Material flow during processing includes:
1. Particle size reduction,
2. Premixing,
3. Mixing,
4. Pelleting, and
5. Sacking.
10.4.4.Packaging

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Most fish feed pellets are sacked. The sacking operation includes: weighing,
sacking, taping, coding, and sewing. The sacked bags are then sent to the
warehouse for distribution.
10.4.5.Storage and Distribution
Bulk products are stored in large bins. Feed is loaded into specially constructed bulk
carriers and delivered to the customer. Feed is discharged from the truck into customer
storage facility by means of an auger system, paddle conveyor, or pneumatic system
Unit 11 - Different forms of feed
11.1.Different forms of feeds
There are two forms of feeds
 Dry feeds
 Non-dry feeds
Dry feeds
Dry feeds are generallymade from dry ingredients or from mixtures of dry and moist ingredients. Generally dry feeds
carry 10-12 % moisture depending on the environmental conditions.
The dry feed is classified in to two groups (1) Mashes/ Meals and (2) Pellets. The mashes/ meals refer to simple
mixtures of dry ingredients. While the pellets refers to ingredients being compacted to give defined shape by a
mechanical means. Depending on the formulation and compacting techniques they may be defined as floating and
non-floating (sinking) pellets.
Non-dry feeds
The non-dry feeds are composed of two types (1) wet feeds and (2) moist feeds. The wet feeds are generally made
from trash fish, slaughter house wastes etc. which contain 45-70% moisture. The moist feeds on the other hand are
made from mixtures of wet and dry raw materials or from dry ingredients to which water is added. The moisture
content ranges from 18-40%.
11.2. Feeds based on life-cycle of fish
Feeds can be classified based on the stage of the life cycle at which they are targeted.
Starter feeds
Starter feeds are given as first feeds to feed the fry or larvae, when their yolk is exhausted or about to be exhausted.
The transformation from an endogenous to an exogenous food supply is critical and thus starter feeds should be
nutritionally complete, easily digestible, and with appropriate particle size. Starter feeds are generally in the form of
fine crumbles or flakes. However, in the case of shrimps starter feeds are given to post larvae up to 0.5 g size
juveniles.
Fry feeds
Fry is the term used for the unmetamorphosed young stage in the life cycle of fish. Fry feeds generally contain higher
levels of protein because the protein and energy requirements are high in the early stages oflife because the highest
relative weight gain is achieved in the fry stages. Fry feeds are generally in the form of flakes or crumbles.
Fingerling feeds
The fingerling stage is defined as metamorphosed younger stage offish to a growth of about 10-20g.Fingerling feeds
vary from crumbles to pellets depending on the species to be cultured and their size. Fingerling diets tend to contain
less protein and energy than fry and starter diets.

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Grow-out feeds
The weightincrease in fish during this grow-outstage is ata uniform rate, decreasing slightlyas the fish increases in
weight. Thus the nutritional requirement during this stage is rather uniform. It is important to ensure that the protein
that the protein in the feed is used mainly for growth and not for metabolic activity. The biomass increments are
considerable and also the quantity of feed administered is high. Thus, during this stage cost-saving feeds are
essential. Generally pellet form of the feed is employed during grow-out stages.
Broodstock feeds
Adequate nutrition has an important role to play in the reproductive success of fishes. A number of aspects of
reproduction like the time of first maturity, number of eggs produced (fecundity). egg size and egg quality as
measured by chemical composition, hatchability and larval survival can be affected by nutritional status.
It has been shown that essential fatty acids, vitamins (A, E and C), trace minerals and carotenoids can affect
fecundity, egg quality, hatchability and larval quality. Nutritional requirements of broodstock can further differ
depending upon the phase of reproductive period.
Formulation of complete diets should, therefore, take into account the stage-specific, as well as species-specific
nutritional requirements of the broodstock. Nutritionists and the feed industry should also consider the options for
developing three types of broodstock diets:
 conditioning diet
 reproduction diet
 recovery/maintenance diet
The broodstock conditioning diet should be formulated as an optimized growout diet to meet the full nutritional
requirements of the species from commercial to broodstock size. The reproduction diet used before or during
spawning should meetthe needs for maximal reproductive performance (spawning success and fecundity), gamete
quality, and transfer of nutrients and biologically active substances to offspring. The recovery/maintenance diet
should assist recovery from reproductive exhaustion and reconditioning for the next reproductive cycle.
11.5.Flakes
Flake dietformulation can be made with certain commerciallyavailable feedstuffs.The double drum dryer processing
units are readily adapted to large-volume production. Vegetable binders can be used to achieve the water stability
needed to optimize residence time of the flake in the aqueous system. Flakes can be reduced to smaller particle
sizes without reducing the basic stability characteristics.
11.6.Farm-made feeds
Farm-made feeds maybe defined as small scale feed manufacture encompassing everything from simple hand
formed dough balls to small feed production units.Theyare an alternative to commercial feeds.Farm made
aquafeeds can be prepared from a wide range of locally available ingredients.They may consistofsingle raw
materials such as rice bran or groundnutcake,simple mixture ofingredients,or complete formulated compound
feeds compacted by hand or by machine.However,physical qualities offarm made feeds are relatively inferior to
commercial feeds.The costof farm made feeds will usuallybe low.
Some of the drawbacks offarm-made feeds;
 Most of the farm made feed disintegrate easilyand therefore pollute the culture system quickly.
 The availability of trash fish is constantly declining due to the ever increasing demand for live stock feed
preparation
 The quality of feed is mainlydepending on the raw material used.
 Information of the digestibilityof locally available ingredients are notavailable
 The nutritional value of farm made feed is highly variable from place to place.
 The quantity and quality of the farm-made feeds cannotbe controlled.
 Due to poor road connectivity and transportation facility, ingredients are notalways available at the places
and times when they are required.
 Farm-made feeds for large scale production units are notfeasible
Though there are some drawbacks, the use of farm -made feeds in low intensive crustacean farms and carp units
remains a viable option. If properly prepared, farm-made feed can provide all essential nutrients and proper growth

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rate can be achieved. There is a potential for improved profitability in small scale aquaculture units through farm -
made feeds.
Unit 12 - Feed additives
12.1.Binders
In order to avoid disintegration of feed and dissolution in water suitable binding agents are necessary.
Binders are substances used in diets to improve their pelletability, enhance their durability, preserve their
physical form during storage and to preserve the water stability. In India the commonly employed binder
in fish feed pellets is tapioca, wheat flour and rice flour. The other types of binders used in compounded
feeds are caboxymethylcellulose (CMC), hemicellulose, bentonites, agar, carragenin and collgen. Heat
treatment during diet preparation results in gelatinization of carbohydrates and thus helps in binding the
resultant feed. Any binder chosen for fish feed pellets should have water stability for a minimum period of
3 hours. The binder apart from enhancing pellatability must also serve as a source carbohydrate in the
feed. A binder should be inexpensive and should be easily available.
Unit 12 - Feed additives
12.2.Antioxidants
The oxidative rancidity or lipid peroxidation results in a serious decrease in the energy value of a fat or oil.
Undesirable oxidation in feeds may be combatted in several ways. Care should be used to make certain
that the ingredients included in the feeds provide adequate margins of safety of vitamins A, E, and other
natural antioxidants; e.g., lecithin. The use of unstable fats and oils or other pro-oxidants in the feed
should be minimized whenever possible.
Antioxidants have been used in commercial fish feeds. Although hundreds of chemicals have been
tested, only a few have shown the qualifications necessary to make them suitable for use in preventing
undesirable oxidations in feedstuffs, in finished feeds.
Some of the important anti-oxidants used in fish feed are
 Ethoxyquin (1,2-dihydro-6-ethoxy-2,2,4- trimethyl quinoline)
 BHA (butylated hydroxy anisole)
 BHT (butylated hydroxy toluene)
The level of different anti-oxidants used in the fish feed is given below.
 ethoxyquin: 150 ppm
 BHT: 200 ppm
 BHA: 200 ppm.
12.3.Enzymes
One of the major problems associated with the use of plant proteins in fish feed is the presence of anti-
nutritional factors, such as phytate (myo-inositol-1,2,3,4,5,6-hexakisphosphates), which is the main
storage form of phosphorus. Up to 80% of the total P content in plants may be present in the form of
phytate and is practically not available for fishes due to lack of intestinal phytases for efficient phytate
hydrolysis during digestion. Therefore, most of the phytate-phosphorus ends up being excreted into the
water which may cause pollution in terms of algal growth.

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Phytase, an enzyme specific to hydrolyze indigestible phytate, has been increasingly used in fish feed
during the past two decades, mainly in response to heightened concerns over phosphorus pollution to the
aquatic environment. Phytase supplementation also leads to improved availability of other minerals and
trace elements.
Nevertheless, there is still no consistent conclusion that phytase could enhance protein and energy
utilization. Studies in amino acid digestibility after phytase supplement are mutative and the underlying
mechanisms have not been fully understood. Because phytase is very sensitive to pH and temperature,
the utilization of phytase in fish feed is still on its first stage.
12.4.Pigments
Carotenoids are the most important classes of pigments for fish and crustaceans. Canthaxanthin and
astaxanthin add colour to the flesh and eggs. High-value culture species such as salmon and red sea
bream do not have the ability to convert xanthophylls to carotenoids, and therefore must receive these
pigments in their diets. Carotenoid supplementation is provided to these species by adding natural
material containing the specific pigments such as paprika, krill products and processing waste of shrimp
and crab.
12.5.Growth promoters
17 beta methyl testosterone incorporated in the diets has shown better growth in Indian major carps and
also in common carp. While a combination of 17 alpha methyl testosterone and diethylstilbestrol has
resulted in faster growth in silver carp and Tor Khudree. But these anabolic steroids were in use earlier as
feed additives but the growing concern about hormone residues in products destined for the market has
led to the ban in most countries. However, steroids are currently used in the culture of certain species, not
with a view to enhancing growth but with a view to obtaining populations of a single sex population by sex
reversal. This is achieved by giving anabolic steroids in the diets during the fry stages.
Nonsteroid hormones that have growth promoting effect in fish are thyroxine, triiodothyronine, inulin etc.
However their usage is uncommon.
12.6.Feed stimulants
Chemo-attractants are synthetic chemicals or natural ingredients containing chemicals, such as free
amino acids, betaine etc. Generally, extractive compounds in muscles of molluscs and crustacea are
believed to be principal flavour attractants. These attractants are a mix of chemicals comprising
nitrogenous compounds including free amino acids, low molecular weight peptides, nucleotides and
related compound and organic bases.
The diet presented must have the attractiveness (ie. smell or taste) to elicit an optimal feeding response
depending on species in question is a visual feeder or a chemo-sensory feeder. For example, although
marine fish held in captivity generally rely on sight to locate their food, they also rely on chemo-receptors
located in the mouth or externally on appendages such as lips, barbels and fins. The use of dietary
feeding stimulants for these cultivated species is therefore essential to elicit an acceptable and rapid
feeding response. In addition, by using feeding stimulants and improving feed palatability, the period of
time the feed remains in the water can be reduced, thus minimizing nutrient leaching.
Unit 14 - Digestive enzyme, digestibility and factors affecting digestibility
14.1.Digestion and Absorption

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Digestion is the process by which the ingested food material is broken down in to
simple, small, absorbable molecules, while absorption refers to diffusion and active
transport of products of digestion in to fish tissue. Digestion is a progressive process,
beginning in the stomach and possibly not ending until food leaves the rectum as
faeces. The task of digestion is performed primarily by the digestive enzymes, which are
secreted in to the lumen of the alimentary canal from the oesophageal, gastric, pyloric
caecal and intestinal mucosa and from the pancreas.
14.3.Protein digestion
Proteolytic enzymes arise from inactive precursors known as zymogens. Zymogens are
processed in the lumen of the gut either by acid hydrolysis or proteolytic action.
Proteases break down peptide link of proteins. Different enzymes are capable of acting
on peptide bonds either at the end of protein (exopeptidases) or at a point within the
protein (endopeptidases). Endopeptidases or very specific in their action and exert their
effect only at a particular point with in the protein molecule.
14.4.Fat digestion
The liver plays an important role in fat digestion. The bile that is produced in the liver
and stored in gall bladder is released when food arrives in the intestine. It contains gallic
acid of high surface activity and these emulsify the fats, breaking large fat drop lets in to
very small droplets there by increasing the surface area and making them more
accessible to fat splitting enzymes, which are termed as lipolytic enzymes or lipases.
14.5.Carbohydrate Digestion
The carbohydrate digestion is performed by a large number of carbohydrate digesting
enzymes called carbohydrases. Each one of the carbohydrases is very specific in its
actions. Carbohydrases have been demonstrated to be present in pancreatic juice in the
stomach, in the intestine and in the bile, but not necessarily at all sites in all the fishes.
In most species however, the pancreas is the main producer of carbohydrases.
14.6.Microbial digestion
Microbial digestion plays an important role in cellulose digestion and protein synthesis,
particularly cellulase being produced by the bacteria harboured in the gut. Generally
bacteria are abundant in the gut of detrital and macrophyte feeders and also exhibit
considerable proteolytic and amylolytic activity. In addition microbial flora is also known
to exhibit chitinase and lecithinase activity.
14.7.Factors affecting digestibility

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Both biological and environmental factors affect the digestibility. The water temperature,
salinity, fish size and feeding level are known to affect the digestibility.
 Digestion rate and or gastric emptying time are influenced by size of the fish with
juvenile fishes exhibiting faster gut evacuation.
 Decrease in digestion rate with increase in the meal size has been reported in
some fishes.
 Type of food also influences gastric evacuation. For example presence of fat in
the food delays gastric emptying.
 Feeding levels are known to affect digestibility. At lower feeding levels the
apparent digestibility of protein may decrease.
 Increase in temperature increases the metabolic rate and subsequently enhance
the transit of ingesta through digestive tract. Water temperature affects more the
feed intake and results in poor digestibility in fishes.
 Digestibility of lipid sources high in saturated fatty acids is affected by water
temperature, suggesting strong interaction between melting point of lipid with
respect to water temperature, on apparent digestibility of lipids.
 Recent findings have indicated that beef tallow (fat) is highly digestible when
certain quantity of fish oil is present in the diet, indicating the synergistic effect of
polyunsaturated fatty acids on the digestibility of saturated fatty acids.
Unit 16 - Storage of fish feeds
16.1.Storage
The manufacture of an aquaculture diet inevitably entails a storage period for the
finished ration within the factory warehouse or farm store prior to feeding. Adequate
storage conditions are provided so as to prevent deteriorative changes occurring in
nutrient composition through oxidative damage and/or through microbial, insect or
rodent infestation. Prolonged storage may have deleterious effect on the stability of
dietary vitamins and lipids.
The most important environmental factors governing the storage or shelf life of a
manufactured feed are ambient temperature and humidity. Bacterial infestation only

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generally occurs within stored feeds posessing a moisture content in excess of 25%
(equivalent to a relative humidity above 90%). The most common fungi involved in the
spoilage of feedstuffs include Aspergillus, Cladosporium, Penicillium and
Helminthosporioum .
Reduced nutritional value of the stored feed: mould growth results in the loss (through
enzymatic digestion or destruction) of dietary lipids, amino acids (lysine and arginine
being most affected) and vitamins. Estimated losses in metabolisable energy in corn
due to moulding range from 5% to 25% depending on the mould species involved.
Mould growth can cause feeds to cake or clump, to change colour consistency and
flavour, and to become generally less palatable
Certain mould species, and in particular the mould Aspergillus flavus, produce toxic
metabolites or mycotoxins of which Aflatoxin B1, is the most toxic form causing cancer
(tumors) and liver damage in virtually every animal species, including fish. Feedstuffs
which are especially prone to attack by A. flavus include groundnuts, cottonseed and
copra, and to a lesser extent maize, sorghum, sun flower, soybean and cassava.
A common fault in the design of storage buildings is to neglect to provide for an
adequately constructed floor. This, like the walls should be effectively damp-proofed,
and bags containing feeds should always be stored on wooden pallets. Ideally,
moist/semi-moist aquaculture rations should be stored under refrigeration or used on
the same day of preparation to avoid vitamin losses. Similarly, dry pelleted feeds should
be stored under clean dry ventilated conditions, avoiding high temperatures and direct
sunlight. Preferably the prepared feed should be utilized within three months from the
date of manufacture.
Unit 15 - Evaluation of efficiency of fish feeds
15.1.Evaluation of efficiency of fish feed
The feed formulated is generally evaluated for its efficiency like (1) Digestibility
Coefficient, (2) Feed Conversion Ratio (FCR) and (3) Protein Efficiency Ratio (PER)
and Specific Growth Rate (SGR).
Digestibility Coefficient: reflects the capacity of fish to digest various nutrients such as
protein, carbohydrates, fats etc.

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Feed Conversion Ratio: is variously termed as food quotient, food coefficient, growth
coefficient, food conversion ratio or absolute conversion ratio and reflects the weight or
increase in growth relative to the amount of feed consumed.
No reliable data have been obtained on the FCR of supplementary feeds as FCR is
dependent on various factors such as fertility status of water, density of fish population,
period of rearing and environmental and biological considerations of the fish.
Protein Efficiency Ratio: reflects the efficiency of protein in the feed and its conversion
as meat
Specific Growth Rate: refers to the average percentage increase in weight per day over
the experimental growth period.
Unit 17 - Feeding devices and Methods
17.1.Introduction
In fish and shellfish farming,feed accounts for more than 60% of the operational costand thus differentfeeding
methods can be adopted to avoid wastage offeed. The widespread availabilityof durable dry feeds and rapid
advances in control technologyhas led to the introduction ofnumerous types ofautomated systems for delivering fish
feeds.Options for fish farmers range from traditional hand feeding methods to the use of automatic,computer-
controlled systems.The first choice by fish farmers is whether to feed fish by hand or whether to use labor-saving
mechanical or automatic systems.This decision is based on labour cost,scale offarm operation,species being
farmed,types of holding system,hatchery or grow out operation etc.
17.2.Methods of Feeding
There are two broad methods offeeding practices viz.
 Hand feeding or manual feeding
 Mechanized feeding.
Hand feeding
Hand feeding refers to distribution offeed by hand which allows dose observation ofthe appetite and feeding
behavior of cultured fish species,which feed actively at the surface and grown in clear water system.Effective hand
feeding necessitates some initial training and experience iffood wastage is to be avoided.

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The advantage of hand feeding is that, it is possible to adjustthe feed requirements ofthe fish. It also ensures the
observation of behavior of the farmed animal regularlyobserved and anomalies can be addressed.On the other hand
it is disadvantageous as itis labor intensive and time consuming work and limited in its application on large farms.
Mechanized feeding
At present,there are differenttypes of feeding equipments being used.Fish feeders can be divided into two major
groups,as follows:
(a) Stationary feeding equipment
(i) withoutsupplied energy- Example:demand feeders
(ii) with supplied energy-Example:automatic feeders (electric,pneumatic,hydraulic)
(b) Mobile feeding equipment
(i) feeding carts
(ii) feeding boats
17.2.Methods of Feeding
There are two broad methods offeeding practices viz.
 Hand feeding or manual feeding
 Mechanized feeding.
Hand feeding
Hand feeding refers to distribution offeed by hand which allows dose observation ofthe appetite and feeding
behavior of cultured fish species,which feed actively at the surface and grown in clear water system.Effective hand
feeding necessitates some initial training and experience iffood wastage is to be avoided.
The advantage of hand feeding is that, it is possible to adjustthe feed requirements ofthe fish. It also ensures the
observation of behavior of the farmed animal regularlyobserved and anomalies can be addressed.On the other hand
it is disadvantageous as itis labor intensive and time consuming work and limited in its application on large farms.
Mechanized feeding
At present,there are differenttypes of feeding equipments being used.Fish feeders can be divided into two major
groups,as follows:
(a) Stationary feeding equipment
(i) withoutsupplied energy- Example:demand feeders
(ii) with supplied energy-Example:automatic feeders (electric,pneumatic,hydraulic)
(b) Mobile feeding equipment
(i) feeding carts
(ii) feeding boats
17.3.Demand feeder
There are different varieties of demand feeders buttheir general principle is the same.Demand feeders are
controlled by the fish themselves according to their appetite.Some species offish learn very rapidly to use demand
feeders butthey are usuallyunsuitable for small fish which are unable to operate them.

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17.5.Feeding carts Feeding carts can be used efficientlyin intensive fish farming with centralized pond systems
connected via suitable roads.Their operation is notautomatic (unlike the stationaryfeeders) but fully controlled by
the operator.The feeding carts can be self-propelled or tractor pulled.The feed is blown into the fish pond by a turbo
blower.
17.6.Feeding boats
In fish farms having large ponds,feeding boats can be used efficiently. There is a longitudinal slotin the bottom of
these boats through which the feed grain is washed outby water currentduring the movementof the boat.
17.7.Feeding devices for wet or moist feeds
Moist feeds can also be transferred to large cages and ponds more effectively than it can be fed by hand,by using a
mechanical 'thrower'.This is simplya centrifugal fan into which the feed is dropped.
Unit 13 - Non-conventional feed ingredients and anti-nutritional factors
13.1.Introduction
Non-conventional feed ingredients are not usually the traditional ingredients used for commercial fish feed production. Fishmeal is
know n to contain almost complete EAA profile that is needed to meet the protein requirement of most fish species. Since fishmeal is
becoming expensive as a feed ingredient, the use of non-conventional feedstuffs has been reported w ith good grow th and better
cost benefit values.
Selected non-conventional feedstuffs of potential value to aquaculture

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13.2.Soybean meal
Soybean meal appears to be a reasonably good feed component for aquaculture diets w hich contain about 40-45 % protein. It has a
lysine content that approaches that of fishmeal, but it is deficient in the sulphur-containing amino acids and tryptophan. Because of
these amino acid deficiencies, soybean mealcan not be used as the only source of protein and is generally compounded w ith other
feed-stuffs w hen it is used in aquaculture rations. Although the inclusion of soybean meal in fish diets presents no manufacturing
problems but problems relating to palatability and availability of nutrients have been encountered. It is believed that part of the
problem is due to the phytate content of soybeans. Several investigators have demonstrated that heating soybean meal rather
severely not only increases its acceptability to fish, but also improves the availability of nutrients w hich is accomplished by
deactivating trypsin inhibitors.
13.3.Single Cell Protein
Predictions of future protein shortages have spurred research on non-agriculturalmethods of protein production. As a result, certain
types of high protein products suitable for feeding to livestock and fish are now produced on an industrial scale. Notable among
these new protein sources, are single-cellorganisms. Single cell proteins (SCP) are mainly derived from unicellular organisms such
as yeast and bacteria, but can also include fungi and algae. SCP has reasonably w ell balanced amino acid profiles. Bacterial SCP

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also has higher protein content, about 70 percent as compared to 60 percent for yeast. SCP is an excellent source of some vitamins
and minerals and also possesses usable lipids and carbohydrates.
13.4.Krill
Krill meal has been reported to contain 55 percent protein, 10 percent moisture, 10-15 percent fat and 15.2 percent ash. The
remaining portion of the composition is probably chitin.
13.5.Poultry By-Products and Feather Meal
Poultry by-products are primarily used by the pet food industry, and feather meal is a dietary ingredient, in poultry rations. They
appear to be excellent protein and lipid sources containing 69 percent crude protein, 10-21 percent lipid and about 10 percent ash.
13.6.Anti-nutritional Factors
The utilization of non-conventionalfeedstuffsof plant origin had been limited as a result of the presence of antinutitional factors like
alkaloids, glycosides, oxalic acids, phytates, protease inhibitors, haematoglutinin, saponegin, momosine, cyanoglycosides, linamarin
etc., to mention a few despite their nutrient values and low cost implications. These anti-nutritional factors retard grow th and other
physiological activities at higher inclusion levels. Nearly all sources of plant protein possess associated factors w hich mus t be
eliminated by special processing techniques to render them to possess maximum nutritional value.
The follow ing table gives some of the compounds occurring in feedstuffsthat are know n and/or suspended of causing physiological
abnormalities or otherw ise impairing the grow th of fish
Unit 19 - Nutritional deficiency disorders, symptoms and diseases in fishes
19.1.Introduction
The deficiency of various nutrients in a formulated feeds often results in
pathological symptoms/deficiency disorders in fishes. The following gives an
account of nutritional disorders due to deficiency of respective nutrients in feeds.
19.2.Nutritional disordersdue to proteindeficiency

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Apart from the above, nutritional pathologies may arise from the consumption of feed
proteins containing toxic amino acids or their derivatives. Feed proteins containing toxic
amino acids have a negative effect on fish growth and feed efficiencyincluding eventual
death of fish. In addition to the non-essential amino acids, certain EAA (ie. leucine) have
also been reported to exert a toxic effect in fish when present in excesses.
19.3.Nutritional disorders due to lipid deficiency

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19.4.Nutritional disordersdue to mineral efficiency

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