An overview on significance of fish nutrition in aquaculture industry

Abstract

Global aquaculture production is increasing year by year and it is the fastest and reliable sector to fulfil the protein deficiency among the human beings around the world. Various innovative integration and intensification approaches has been adopted for finfish and shellfish culture by many countries. Nutrition and feeding is the significant criteria should be focused for economical and sustainable aquaculture. Sustainable production of aquatic organisms can be obtained by formulating and producing low cost, low polluted and nutrient rich high quality artificial feeds. Like terrestrial animals around 40 essential nutrients are required by the aquatic organisms which includes protein, carbohydrate, fatty acids, vitamins, minerals, growth factors and other energy sources essentially for maintaining growth, reproduction and other normal physiological functions. The variation in the nutritional requirements can be identified with warm water or cold water, finfish or shell fish and marine water or freshwater species. Successful production of good quality fishes can be achieved by feeding the fishes with nutritionally balanced feeds. The nutritional requirements of various fish species are fulfilled by a different animal and plant based artificial feeds. Standardization of feeding method is another innovative way for preserving sustainable production of aquatic organisms in cages, ponds and short seasonal tanks. Ideal fish protein concept is also the superlative advance towards maximizing the effective utilization of protein by the fishes through the production of cost efficient, nutritionally high and low polluted feeds.

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International Journal of Fisheries and Aquatic Studies 2017; 5(6): 349-355
E-ISSN: 2347-5129
P-ISSN: 2394-0506
(ICV-Poland) Impact Value: 5.62
(GIF) Impact Factor: 0.549
IJFAS 2017; 5(6): 349-355
© 2017 IJFAS
www.fisheriesjournal.com
Received: 15-09-2017
Accepted: 17-10-2017
E Prabu
Ph.D. Research Scholar,
Fisheries College and Research
Institute, Ponneri, Chennai,
India
S Felix
Vice Chancellor, Tamil Nadu
Fisheries University,
Nagapattinam, Tamil Nadu,
India
N Felix
Director, Directorate of
Aquaculture Technology
Training and Incubation, Tamil
Nadu Fisheries University,
Muttukadu, Chennai, India
B Ahilan
Dean, Fisheries College and
Research Institute, Ponneri,
Chennai, India
P Ruby
Ph.D. Research Scholar,
Fisheries College and Research
Institute, Ponneri, Chennai,
India
Correspondence
E Prabu
Ph.D. Research Scholar,
Fisheries College and Research
Institute, Ponneri, Chennai,
India
An overview on significance of fish nutrition in
aquaculture industry
E Prabu, S Felix, N Felix, B Ahilan and P Ruby
Abstract
Global aquaculture production is increasing year by year and it is the fastest and reliable sector to fulfil
the protein deficiency among the human beings around the world. Various innovative integration and
intensification approaches has been adopted for finfish and shellfish culture by many countries. Nutrition
and feeding is the significant criteria should be focused for economical and sustainable aquaculture.
Sustainable production of aquatic organisms can be obtained by formulating and producing low cost, low
polluted and nutrient rich high quality artificial feeds. Like terrestrial animals around 40 essential
nutrients are required by the aquatic organisms which includes protein, carbohydrate, fatty acids,
vitamins, minerals, growth factors and other energy sources essentially for maintaining growth,
reproduction and other normal physiological functions. The variation in the nutritional requirements can
be identified with warm water or cold water, finfish or shell fish and marine water or freshwater species.
Successful production of good quality fishes can be achieved by feeding the fishes with nutritionally
balanced feeds. The nutritional requirements of various fish species are fulfilled by a different animal and
plant based artificial feeds. Standardization of feeding method is another innovative way for preserving
sustainable production of aquatic organisms in cages, ponds and short seasonal tanks. Ideal fish protein
concept is also the superlative advance towards maximizing the effective utilization of protein by the
fishes through the production of cost efficient, nutritionally high and low polluted feeds.
Keywords: Aquaculture, Nutrition, Protein, Feeding, Antioxidant, Pigment.
1. Introduction
Aquaculture has sustained a global growth at present and is expected to increasingly fill the
shortfall in aquatic food products. Aquaculture activity is considered as the only alternative for
the development and improvement of fisheries resources and revitalization of ecosystems
(Okechi, 2004) [1]. Fish feeds constitutes 40-60% of the total cost of aquaculture production
which is expensive and led to extensive studies on replacing a costly fish meal in the diets.
Growth performances and survival of aquatic organisms can be influenced by the development
of nutritionally balanced commercial diets (Tom and Van-Nostrand, 1989) [2]. The
improvement of nutritional interventions supports the aquaculture industry sustainable,
economical and nutritious finfish and shellfish production (Robinson et al., 1998) [3].
The science of nutrition draws heavily on findings of chemistry, biochemistry, physics,
microbiology, physiology, medicines, genetics, mathematics, endocrinology, cellular biology
and animal behavior. To the individual involved in aquaculture, nutrition represents more than
just feeding. Nutrition becomes the science of the interaction of a nutrient with some part of a
living organism, including feed composition, ingestion, energy liberation, wastes elimination
and synthesis for maintenance, growth and reproduction. Feeds and feed stuffs contain the
energy and nutrients essential for the growth, reproduction and health of aquatic animals.
Deficiencies or excesses can reduce growth or lead to disease. Dietary requirements set the
necessary levels for energy, protein, amino acids, lipids (fat), minerals and vitamins. The
subcommittee on Fish Nutrition of the Committee on Animal Nutrition of the National
Research Council (NRC) examines the literature and current practices in aquaculture. The
NRC publishes the nutritional recommendations for fishes. Dietary nutrients are essential for
the construction of living tissues. They also are a source of stored energy for fish digestion,
growth, reproduction and the other life processes. The nutritional value of a dietary ingredients
is in part dependent on its ability to supply energy. Physiological fuel values are used to
calculate and balance available energy values in prepared diets. They typically average 4,

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4 and 9 kcal/g for protein, carbohydrate and lipid respectively
(Helfrich and Smith, 2001) [4].
Prepared or artificial diets may be either complete or
supplemental. Complete diets supply all the ingredients
(protein, carbohydrates, fats, vitamins and minerals)
necessary for the optimal growth and health of the fish. Most
of the commercial diets containing the essential nutrients
including protein, lipid, carbohydrate, ash, phosphorous,
water, minerals and vitamins in the range of 18-50%, 10-25%,
15-20, <8.5%, <1.5%, <10%, 0.5 and 0.5 respectively.
Natural foods may not available for the aquatic organisms
which are culturing in the indoor systems or confined cages,
hence the nutritional need of this cultured organisms can be
fulfilled only by the addition of nutritionally enriched
supplementary feeds (Craig and Helfrich, 2009) [5].
2. Digestion and Absorption
The digestive or gastrointestinal tract is described as a
continuous, hollow tube extending from the mouth to the anus
with the body build around it. The digestive system of fish
includes the mouth, pharynx, esophagus, stomach, pylorus,
intestine, liver and gall bladder. It acts like an assembly line
in reverse, taking the feedstuffs apart to their basic chemical
components so that the fish can absorb them and rearrange
them into its own characteristic body composition. Table 1
summarizes all structures of the digestive system in digestion
and absorption. Other considerations of digestion and
absorption in fish include the type of eaters, the anatomy of
the mouth and feeding behavior (Fagbenro, 1998) [6].
Table 1: Digestive system structures and functions
Structure Functions
Teeth Grasping, holding, crushing, depending on species
Pharynx Opening to the gills
Esophagus Short, Simple passage to stomach, lined with mucus secreting cells
Stomach Walls lined with cells secreting hydrochloric acid and pepsinogen for initial stages of protein digestion;
holding compartment for feed
Pyloric cecum Secretes enzymes for digestion; Increased surface area for absorption of nutrients
Intestine Secretes enzymes for digestion; Increased surface area for absorption of nutrients
Gall bladder Stores and releases bile for digestion and absorption of fats
Liver Synthesis or storage from absorbed nutrients, production of bile, removal of some waste products from blood
3. Feeding type and anatomy
Fish can be divided into three types of eaters
1. Carnivores consume primarily animal material. Foods
consumed by this type of fish may be as small as a
microscopic crustacean or insect or as an amphibian or a
small mammal.
2. Herbivores subsist primarily on vegetation and decayed
organic material in the environment.
3. Omnivores consume almost any food source, either plant
or animal origin.
Certain anatomic changes in the mouth of fish occurred
through evolutionary development. Fish can be classified
according to their feeding habits into the following categories:
 Predators: Trout are an example of fish that feed on
animals generally large enough to be seen with the naked
eye. Teeth are well developed and act as a means of
grasping and holding the prey. Some predator rely
primarily on sight to hunt, whereas others rely on the
senses of taste and touch or on lateral line sense organs.
 Grazers: The mullet is an example of a fish that grazes
in the same sense as mammalian grazers. Generally,
mullets graze continuously on the bottom of the water
habitat for either plants or small animal organisms. Food
is taken in well-defined bites.
 Strainers: The menhaden is an example of a fish that
selects food primarily by size rather than type. An adult
menhaden can strain in excess of 6 gal of water per
minute through its gill rakers. Through this process of
rapid straining, the menhaden able to concentrate a
relatively large mass of plankton and other organisms.
 Suckers: The buffalo fish is an example of a fish that
feed primarily on the bottom of its habitat, sucking in
mud and filtering and extracting digestible material.
 Parasites: Some fish, like the lamprey, attach themselves
to other animals and exist on the host’s body fluids.
4. Protein requirements
Proteins are long chains of amino acids linked by bonds called
peptide bonds. All amino acids contain nitrogen, so all
proteins contain nitrogen. In fact, measuring nitrogen content
is a method of calculating protein content. Metabolism of
protein for energy produces nitrogen end products. Fish
eliminate these through gills, feces and urine. These nitrogen
end products can cause problems in fish ponds. Protein is the
major concern during formulation of fish feed. It is the most
expensive for fish feed and the most important factors that
contributing to the growth performance of cultured species
(Deng et al., 2011) [7].
Protein serves three purposes in the nutrition of fish:
1. Provide energy
2. Supply amino acids
3. Meet requirements for functional proteins- enzymes and
hormones and structural proteins
The requirement for protein in fish diets is essentially a
requirement for the amino acids in the dietary proteins. Some
amino acids the fish cannot synthesis are called indispensable
or essential amino acids
1. Arginine
2. Valine
3. Histidine
4. Isoleusine
5. Leucine
6. Lysine
7. Methionine
8. Threonine
9. Tryptophan
10. Phenylalanine

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Some of the dietary requirements for methionine and
phenylalanine can met by the amino acids cysteine and
tyrosine respectively. The amino acid requirement given by
the NRC is shown in table 2 for catfish, trout, salmon, carp
and tilapia. Research evidence suggests that large differences
exist among fish species in their requirements for amino
acids. Some of these differences are probably caused by
differences in growth rate, feed intake and the source of
amino acids in the diet. When proteins in most feedstuffs are
properly processed, they are highly digestible. For a variety of
protein rich-feed stuffs, the digestibility ranges from 75 to 95
percent. As dietary carbohydrate increases, the digestibility of
protein tends to decline. Also, overheating during drying or
processing reduces proteins nutritive value. But, insufficient
heating of soybean meal decreases the availability of protein.
Protein requirements for fish are considerably higher than
those for warm blooded land animals. Protein requirements of
fish decline with age. Animal protein sources are generally
considered to be of higher quality than plant sources, but
animal protein costs more. In diets, a combination of protein
sources yields better conversion rates than any single source
(Pandey, 2013) [8].
Table 2: Protein and Amino acid requirement for finfish (NRC, 1993) [9].
Channel Catfish Rainbow trout Pacific salmon Common carp Tilapia
Energy Base
b
(Kcal DE/Kg diet) 3000 3600 3600 3200 3000
Crude protein (%) 32 (28) 38 (34) 38 (34) 35 (30.5) 32 (28)
Amino acids %
Arginine 1.20 1.5 2.04 1.31 1.18
Histidine 0.42 0.7 0.61 0.64 0.48
Isoleucine 0.73 0.9 0.75 0.76 0.87
Leucine 0.98 1.4 1.33 1.00 0.95
Lysine 1.43 1.8 1.7 1.14 1.43
Metheonine + Cysteine 0.64 1.0 1.36 0.94 0.90
Phenylalanine+ Tyrosine 1.40 1.8 1.73 1.98 1.55
Threonine 0.56 0.8 0.75 1.19 1.05
Tryptophan 0.14 0.2 0.17 0.24 0.28
Valine 0.84 1.2 1.09 1.10 0.78
Fish do not have the ability to use non-protein nitrogen
sources. Such nonprotein nitrogen sources as urea and
diammonium citrate, which even non-ruminant animals can
use to a limited extent, have no value as a feed source for fish.
In fact, nonprotein nitrogen can be toxic at high levels. A
protein deficiency or indispensable amino acid deficiency is
observed as a reduction in weight gain. But some specific
amino acid deficiencies manifest as disease conditions.
Cataracts from salmonids, including rainbow trout, when
given diets are deficient in methionine or tryptophan. A
tryptophan deficiency also causes a lateral curvature of the
spinal column or scoliosis in some salmonids. In trout, a
tryptophan deficiency disrupts the metabolism of the minerals
calcium, magnesium, sodium and potassium. In fish diets,
protein and energy should be kept in balance. A deficiency or
excess of energy reduces the growth rates. When dietary
energy is deficient, protein is used for energy. When dietary
energy in excess, feed consumption drops and this lowers the
intake of the necessary amounts of protein for growth
(Abowei and Ekubo, 2011) [10].
5. Carbohydrates
Carbohydrates are the most economical and inexpensive
sources of energy for fish diets. Although not essential,
carbohydrates are included in aquaculture diets to reduce feed
costs and for their binding activity during feed manufacturing.
Dietary starches like cassava starch are used in the extrusion
production of floating feeds. Floating feeds for the various
finfishes are prepared with varying ranges of carbohydrates
(Robert, 1979) [11].
Fishes are having the capability of digesting simple sugars
efficiently. Digestibility will get decrease rapidly when the
sugar becomes larger and more complex. Warm water fish
can digest dietary carbohydrates efficiently when compared
with cold water or marine fish. Utilization of carbohydrates as
an energy source varies with different species. There is no
recommended levels or ranges by national research council
for formulating and preparing finfish and shellfish feeds.
Some form of digestible carbohydrate should be included in
the diet. Carbohydrates improve growth and provide
precursors for some amino acids and nucleic acids. Also,
carbohydrate is the least expensive source of dietary energy.
In warm water fish, cereals grains provide an inexpensive
source of carbohydrates, but their use is limited in cold water
fish. Digestible carbohydrates in trout feed are generally
lower than the levels in catfish feed. In nutrition,
carbohydrates spare protein because less protein will be will
be used for energy. An excess of dietary carbohydrates can
cause livers to enlarge and glycogen to accumulate in the
liver. A general recommendation is a diet of no more than 12
percent digestible carbohydrates. Fats and proteins supply
most of the energy in fish diets (Parker, 2011) [12].
6. Fat
Each gram of fat contains 2.5 times the energy in a gram of
carbohydrates or proteins. The digestibility of fat varies,
depending on
 Amount in the diet
 Type of fat
 Water temperature
 Degree of unsaturation
 Length of carbon chain
Animal fats and fats that are highly saturated have a lower
digestibility. On the other hand, in highly unsaturated fats –
fats that fish can rapidly digest- there is danger of oxidation of
the fats, resulting in feed spoilage. Antioxidants are routinely
added to most fish diets to prevent fats from becoming rancid
in storage. Besides being an important source of energy for
fish, dietary fats provide essential fatty acids (EFA) needed
for normal growth and development. Fish cannot synthesize
these fatty acids. Also, dietary fats assist in the absorption of
fat-soluble vitamins. Freshwater fish require a dietary source

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of linoleic acid and linolenic acid. These are both 18 carbon
fatty acids. Marine fish, like the yellow tail or red sea bream,
require a dietary source of eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA). These are 20 ad 22 carbon fatty
acids respectively. Channel catfish, coho salmon and rainbow
trout require linolenic acid or EPA or DHA. Table 3 indicates
the essential fatty acid requirement for several species of fish
(Parker, 2011) [12].
Table 3: Essential fatty acid requirements of fishes (NRC, 1993) [9]
Species Requirement
Channel catfish 1.0 to 2.0% linoleic acid or 0.5 to 0.75% EPA and
DHA
Chum salmon 1.0% linoleic acid and 1.0% linolenic acid
Coho salmon 1.0 to 2.5% linolenic acid
Common carp 1.0% linoleic acid and 1.0% linolenic acid
Rainbow trout 0.8% to 1.0% linolenic acid 20% of fat as linoleic
acid 10% of fat as EPA and DHA
Tilapia 0.5% to 1.0% linoleic acid
Red sea bream 0.5% EPA and DHA
Yellow tail 2.0% EPA and DHA
Essential fatty acid deficiency sings include skin lessions,
shock syndrome, heart problems, reduced growth rate,
reduced feed efficiency, reduced reproductive performance
and increased mortality. In the body essential fatty acids
function as a part of cell membranes and precursors of
biochemical that perform a variety of metabolic functions.
Fish diets are formulated to meet the optimum ratio of energy
to protein for each species. Fats serve as an important source
of energy, but no definite percentage of dietary fat can be
given without considering the type of fat, as well as the
protein and energy content of the diet. Too much dietary fat
can result in an imbalance of the digestible energy to crude
protein ratio and excessive deposition of fat in the body cavity
and tissues (Endinkeau and Kiew, 1993) [13].
7. Vitamin requirements
Vitamins are organic compounds required in the diet for
normal growth, reproduction and health. They function in a
variety of chemical reactions in the body. The simple
digestive system of the fish establishes a definite need for the
supplementation of vitamins in fish diets. Vitamin
requirements for fish resembles those of nonruminant animals
such as pigs and chickens. Fish and humans are among the
few higher animals that require a dietary source of vitamin C
(Halver, 1985) [14].
Vitamins are divided into two categories, water soluble and
fat soluble.
Water-soluble vitamins include
 Thiamin
 Riboflavin
 Pyridoxine
 Pantothenic
 Niacin
 Biotin
 Folate
 Vitamin B12
 Choline
 Myoinositol
 Vitamin C
Choline, myoinositol and Vitamin C serve a variety of
functions. Choline function as a:
 Component of membranes
 Precursor of acetylcholine, a chemical for nerve
transmission
 Provider of methy groups for chemical reactions
Myoinositol is also a component of membranes and is
involved in sending signals during several body processes.
Vitamin C is involved in the formation of connective tissue,
bone matrix and wound repair. It also facilitates the
absorption of iron from the intestine and helps prevent the
peroxidation of fats in tissues. Most water soluble vitamins
serve as coenzymes in the body’s biochemical reactions.
Enzymes are biological catalysts. Most enzymes are proteins
and they are unique for each biochemical reaction.
Coenzymes then work with or become part of an enzyme
(Parker, 2011) [12].
The fat soluble vitamins are
 Vitamin A
 Vitamin D
 Vitamin E
 Vitamin K
Fat soluble vitamins are absorbed in the intestine along with
fats in the diet. Unlike water soluble vitamins, fat soluble
vitamins can be stored in body tissues. Excessive amounts in
the diet can cause a toxic condition called hypervitaminosis.
Functions of the fat soluble vitamins are quite specific.
Vitamin A is necessary for sight, proper growth, reproduction,
resistance to infection and maintenance of body coverings. As
many land animals, fish can use betacarotene as a Vitamin A
precursor. Vitamin D helps the body mobilize, transport,
absorb and use calcium and phosphorous. It works with two
hormones from an endocrine gland, the parathyroid. Vitamin
E is the name given to all substances that act like alpha-
tocopherol. Vitamin E working with selenium, protects cells
against adverse effects of oxidation. Vitamin K is required for
the normal blood clotting process. Many animals can
syntheses vitamin K in their intestines (Woodward, 1994) [15].
8. Mineral requirements
Fish can absorb a number of minerals directly from the water:
calcium (Ca), magnesium (Mg), sodium (Na), potassium (K),
iron (Fe), zinc (Zn), copper (Cu) and selenium (Se). This
reduces the mineral requirement in the diet. But this also
makes research on dietary mineral requirements difficulty and
inconclusive. Most researchers agree that fish require all of
the minerals required by other animals. Based on their
requirement or use of an animal, minerals are divided into two
groups: macrominerals and microminerals. Macrominerals are
present in the body in relatively large quantities. The
macrominerals include:
 Calcium (Ca)
 Chlorine (Cl)
 Magnesium (Mg)
 Phosphorous (P)
 Potassium (K)
 Sodium (Na)
Calcium and phosphorous are most directly involved in the
development and growth of the skeleton and they act in
several other biochemical reactions. Fish absorb calcium
directly from the water by the gills and skin. The requirement
for calcium is determined by the water chemistry (Athithan et
al., 2013) [16].

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Dietary phosphorus is more critical. Phosphorous is derived
from dietary phosphate. Phosphorous deficiency sings include
poor growth, reduced feed efficiency and bone deformities.
The availability of phosphorous in feedstuffs varies widely.
Feedstuffs from seeds contain phosphorous in a form known
as phytin. The availability of phosphorus in phytin is low.
Simple stomach animals lack the enzyme to release the
phosphorus (Davis and Gatlin, 1996) [17].
Magnesium functions with many enzymes as a cofactor. The
dietary requirement can be met from either the water or the
feed. Deficiencies of magnesium cause anorexia, reduced
growth, lethargy, vertebrae deformity, cell degeneration and
convulsions. Sodium potassium and chlorine are electrolytes.
Sodium and chlorine reside in the fluid outside the cells.
Potassium resides inside the cells- an intracellular cation.
Because of the abundance of these elements in the
environment, deficiency signs are difficult to produce.
Microminerals are present in very small amounts in the bodies
of fish, but they are still important to fish health.
The microminerals include:
 Copper (Cu)
 Iodine (I)
 Iron (Fe)
 Manganese (Mn)
 Selenium (Se)
 Zinc (Zn)
Copper is a part of many enzymes and it is required for their
activity. Although it is necessary for fish health, copper can
be toxic at concentrations of 0.8 to 1.0 m per liter of water.
Fish are more tolerant of copper in feed than in water. Iodine
is necessary for the formation of hormones from the thyroid
gland. Fish can obtain iodine from either water or feed.
Similar to land animals, a deficiency causes the thyroid gland
to grow, a condition similar to goiter (Halver and hardy,
2002) [18].
Iron is necessary for the formation of heme compounds.
These compounds carry oxygen. Because natural waters are
low in iron, feed is considered the major source of iron. Iron
deficiency causes a form of anemia. At high levels, iron can
be toxic and cause reduced growth, diarrhea, liver damage
and death. Manganese functions as a part of enzymes or as a
cofactor. Although it can be absorbed from the water, it is
more efficiently absorbed from the feed. A deficiency causes
reduced growth and skeletal abnormalities.
Selenium protects cells and membranes against peroxide
danger. Selenium deficiencies cause reduced growth. Both
selenium and vitamin E are required to prevent muscular
dystrophy in some species. When dietary selenium exceeds 13
– 15 mg per kg of dry feed, it becomes toxic resulting in
reduced growth, poor feed efficiency and death. Zinc is also a
part of numerous enzymes. Dietary zinc is more efficiently
absorbed than that dissolved in water. Dietary calcium and
phosphorous, phytic acid protein type, all affect zinc
absorption and use. A zinc deficiency causes suppressed
growth, cataracts, fin and skin erosion, dwarfism or death.
Other trace minerals such as fluoride and chromium may be
important but evidence is limited (NRC, 1993) [9].
Other dietary components
Many fish diets contain other ingredients that can affect them.
Some of these ingredients are natural, others are added. These
ingredients include substances such as water, fiber, hormones,
antibiotics, antioxidants, pigments, binders and feeding
stimulants.
9. Water
All diets contain water. The water may be a part of the
feedstuff, come from the air or be added. The less water in a
diet, the easier the storage and handling. When moisture in a
diet exceeds 12 percent, the feed is more susceptible to
spoilage. Some commercial diets contain high moisture levels
because fish seems to prefer moist feed (Lovell, 1989) [19].
10. Fiber
Fiber refers to plant material such as cellulose, hemicellulose,
lignin, pentosums and other complex carbohydrates. These
are indigestible and they do not play an important role in
nutrition. Fiber adds bulk to a feed but increases the amount
of fecal material produced. The goal in commercial
aquaculture is to limit the diets fiber content and use highly
digestible feeds (Krontveit et al., 2014) [20].
11. Hormones
Researchers have evaluated the use of various natural and
synthetic hormones of fish. These hormones include growth
hormone, thyroid hormones, gonadotropin, prolactin, insulin
and various steroids like androgens and estrogens. Hormones
are used for two purposes: (1) Induced or synchronized
spawning and (2) Sex reversal. Induced or synchronized
spawning increases the availability and dependability of seed.
Sex steroids reverse the sex of salmonids, carps and tilapia,
producing a monosex culture of sterile fish. This improves
growth rate, prevents sexual maturation and reduces flesh
quality (Prins et al., 2016). [21]
12. Antibiotics
With the arsenal of antibiotic available for humans and other
livestock, only two have received FDA approval for use in
fish that are sulfadimethoxine / ormetoprim and
oxytetracyclin. When these antibiotics are used in the, the
quantity fed, the feeding rate and the withdrawal time must be
strictly controlled. Only licensed manufacturers can add
antibiotics to feed in the United States. Unlike livestock, fish
do not demonstrate any benefit from sub therapeutic levels of
antibiotics in their feed (Pruden et al., 2013) [22].
13. Antioxidants
Fish feeds containing high levels of fats often use
antioxidants. Oxidation of the fats affects the nutritional
values of the fat and some vitamins. Synthetic vitamin E in
diets usually less little antioxidant activity, so synthetic
antioxidants like ethoxyquin, BHT, BHA and propyl gallate
are used (Wang et al., 2016) [23].
14. Pigments
Pigmentation of the skin and flesh in fish comes from
carotenoids. Fish cannot make these carotenoids, so they must
be present in the diet. In salmonids, the carotenoids
astaxanthin and canthaxanthin are responsible for the red to
orange color of their flesh. In the wild, these carotenoids
come mainly from zooplankton. Some of the natural materials
used to pigment the flesh of salmonids include crab, brill,
shrimp and yeast. Yellow pigmentation of the flesh of catfish
is undesirable. It is caused by the carotenoids lutein and
zeaxanthin from plant material in the diet (Ramya et al.,
2016) [24].
15. Pellet Binders
Binders improve stability in the water, firmness and reduce
fines during processing and handling. Widely used binders are

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sodium and calcium bentonites, lignosulfates,
carboxymethylcellulose, hemicellulose, guargum alginate and
some new inert polymers.
16. Feeding stimulants
The acceptance of the fish feed is determined by the smell and
attractants of the feed. Many researchers are focusing on
increasing the palatability and acceptance of feed for
increasing the feed utilization. This is especially important in
starter and larval feeds. In general, carnivorous fish respond
to alkaline and neutral substances. Herbivorous fishes respond
to acid substances. Besides increasing feed consumption,
some compounds act as deterrents (Barry et al., 2017) [25].
17. Conclusion
Nutrition and feeding influences the growth, reproduction and
health performances of fishes and their response to
physiological and environmental stressors and pathogens. In
seems that nutrition is the heart of aquaculture. Feeding the
fishes with nutritionally enriched feeds may dramatically
increase the overall production. So nutrition is one of the
essential area to be focused by aquaculture industry. Cage
culture in inland open waters is a fast growing activity and
using low quality feeds could have some environmental
impacts. So the production of high quality cum low polluted
feeds for cage culture systems may reduce the negative
impacts on environment by aquaculture activities and brings
the inland fish farmers towards cage culture. The fish farmers
are struggling hard to reduce the cost of fish feed since fish
feed accounts for over 50% of the total cost of fish
production. Many researches are currently undergoing
towards the development of cost efficient feed for enhancing
the fish and shrimp production. Replacement of fish meal
with various plant based ingredients will be a superior way to
reduce the cost of the fish feed without changing the
nutritional profile. There are several plant based ingredients
like soybean meal, rapeseed meal, cottonseed meal, cassava
starch, canola meal, corn gluten meal, ipil ipil meal sesame
meal, corn starch could be used to replace fishmeal in the fish
diet.
Though fish convert feed to human food very efficiently, the
feeding cost of production needs to be controlled. Feeding
fish require an understanding of the process of digestion, the
digestive system and fish nutrition. Fish consume feed for
energy. They use this energy for growth, activity and
reproduction. In the fish diet, feeds containing protein, fats
and carbohydrates supply energy. These feeds enter the
digestive system, where enzymes break down the protein, fats
and carbohydrates to simpler compounds that the fish uses for
energy and to form tissue, enzymes and bone. Protein in the
diet also supplies 10 essential amino acids and fat in the diet
supplies essential fatty acids. Fat soluble and water soluble
vitamins are also supplied by the diet. Minerals are supplied
by the diet and by the water. Feed additives and attractants are
added into the fish diets to increase the growth performances,
immunity, survival, effective feed utilization and feed
acceptance. With the great understanding of the nutritional
aspects, it is very much possible to make the feed nutritionally
balanced. So that higher growth, best food conversion ratio
and less polluting to the environment could be achieved.
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