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Role of Nutrition in Fish Seed
Production
A. P. SharmaDean
College of Fisheries
G.B. Pant University of Agriculture &Technology, Pantnagar
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Food requirement of fishes
Energy is needed for the maintenance of all
living organisms
Most plants obtain their energy directly from the
sun and use that energy to synthesize the
complex molecules which make the structural
and storage parts of the plant
Animals get their energy from oxidation of complex molecules which are eaten by the
animals
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Food requirement of fishes
The energy in feed is not available untilthe complex molecules are broken downto simpler molecules by digestion
The ability to digest feed by different fishspecies is different
The food requirements of different species
vary greatly Energy is stored in the chemical structure
of the complex molecules of feed materials
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Energy requirement Feed provide maintenance energy first
then the remaining energy is used for increasing growth
The requirement of energy of fishes is lessthan birds and cattle
When feed has excess amount of energy,the fishes stop feeding (excess amount of
energy reduces feed consumption) Theexcess amount of energy leads to fatdeposition and reduce the dress out
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Nutrient requirement of fishes
There are two aspects for this
What is the energy content and what is the
protein content of feed In general, if the protein requirement is full
filled, the energy requirement already be
full filled
It means energy protein ratio is important
Highly proteinacious diet is also harmful
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Nutrient requirement of fishes
8- 9: 1 :: energy : protein ratio is found
satisfactory for carps (max. growth is
obtained at 8.7- 9.1: 1) If the feed has 32% protein formed with
50% soybean meal, 40% grains, 8%
animal products and 2% vitamins and
minerals. This contain 2.8 k cal digestibleenergy/ g of dry feed of this
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Feeding strategies
Determine how much should be fed
(Ration size)
Determining how many times the organismshould be fed in the day and optimum time
of feeding
Efficiently broadcasting the predetermined
ration to the system
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Feeding strategies (Ration size) An optimum ration is one which gives the best
growth and FCR (Results in minimum wastageand minimum deterioration of the water quality
Ration size is variable (A juvenile fish requiresmore energy per unit weight for metabolism and
has potential to grow faster than an adult fishand need higher ration)
Water temp. also affects feeding rate
Ration size is calculated as a percentage of thebiomass present
Ideally feeding rate should be adjustable daily
Daily feed requirement Body weight to be fed daily (%)= FCRx3xAX100
B
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Feeding frequency
Important to ensure maximal FCR and dress weight ofthe cultured organism
For optimum growth and feed conversion, each feedshould ideally be 1% of the body weight
Survival is not significantly influenced by feedingfrequency once the transition from an endogenous to anexogenous food supply is complete.
Higher feeding frequencies reduce starvation andstunting, thereby resulting in uniformity in size
Dry feed need to be distributed more frequently thanmoist
At least 90% of the presented feed should be consumedwithin the first 15 minutes of the feeding time
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Feeding frequency
Important to ensure maximal FCR and dress weight ofthe cultured organism
For optimum growth and feed conversion, each feedshould ideally be 1% of the body weight
Survival is not significantly influenced by feedingfrequency once the transition from an endogenous to anexogenous food supply is complete.
Higher feeding frequencies reduce starvation andstunting, thereby resulting in uniformity in size
Dry feed need to be distributed more frequently thanmoist
At least 90% of the presented feed should be consumedwithin the first 15 minutes of the feeding time
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Feeding Rate
Fish Weight (g) Feeding rate (%) Feeding frequency
(time/day)25 4.5 3
50 4.0 3
75 3.6 3
100 3.3 3
150 3.1 2
200 3.0 2
250 2.6 2
300 2.4 2
400 2.1 2
500 1.7 2
600 1.4 2
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Feed ingredients
Carotenoid supplements- Xanthophylls
and carotenoids are the most important
classes of pigments for fish and
crustaceans. Canthaxanthin and
astaxanthin add colour to the flesh and
eggs
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Type of feed
Starter feed Larger than 400 , good growth can be obtained, must be
readily consumed by fish, highly digestible, highly watersoluble
Fry feed For 0.5- 0.75 g fry, contain high level of protein
Transition feed High palatability, high energy content, formed with relatively
low digestibility coefficients
Fingerling feed Semi moist feed pellet sizes of 3/ 64- 3/ 32 inch, growth rates
are higher during this stage, high protein and vitamin content
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Type of feed
Grower feeds Given from fingerling stage to market size, contain
less protein and more energy
Brood stock feed Most of the brooders require -3 fatty acids,
protein, energy and vitamin requirement is high,
ascorbic acid level should be high
Low pollution feeds Phosphorus and nitrogen level should be reduced
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Type of feed
Microencapsulated feeds Micro encapsulation is a process in which a
material surrounds and coats another substance
Adopted and developed for larval feeds
Micro capsules are separated into two categories
impermeable and controlled release
The most common and appropriate are cross-
linked proteins and lipid walled microcapsules Primary goal is to reduce the leaching loss
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Feed manufacturing
Basic steps are grinding, mixing, conditioning,
pelleting, cooling, top dressing, sacking, storing,
and shipping
Sacked or bulk ingredients are arrive at feedmills, should be examined for condition
Drugs and medication must be segregated
Ingredients must be stored to protect againstcontamination, moisture and pest damage
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Feed manufacturing
Grinding Most of the ingredients need to be ground before
use
Grinding increases the surface area of ingredientparticles, facilitating mixing and pelleting Grindingis done by hammer mills, pulverizers, attrition mills
Particles are reduced to various sizes, dependingupon the process by which the feed will be pelleted
Ingredients with high lipid content are more difficultto grind than low lipid ingredients.
High lipid ingredients can be combined with lowlipid ingredients
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Feed manufacturing
Mixing To produce a homogenous blend
Ingredients are generally added to the mixer in a
predetermined sequence to ensure adequatemixing
Dry ingredients are first combined, after sufficient
mixing of dried ones liquid ingredients are added
Batch or continuous mixers are common. Type ofmixer includes horizontal ribbon mixers, vertical
mixers, Nanta mixers, turbine mixers
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Feed manufacturing
Conditioning and expansion Done for pelleting and includes thermal and physical
processing
Feed ingredients are kept for very short time about 30 sec
Expansion is a conditioning step, involves steam injectionand mixing
Pelleting Convert the homogenous blend of ingredients into durable
particles and make them suitable for feeding
Compressed Pelleting
Exposed to dry steam for about 5- 25 sec. to increase the temp.to about 850 C and the moisture to about 16% through holes ina metal die
They are cut by a stationary, adjustable knife, fat level shouldbe more than 2- 3%
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Feed manufacturing
Extruded dry pelleting
More versatile than compression pelleting, thereby
allowing for the control of pellet density
Temperature increased up to 125- 150 0 C in a
pressurized conditioning chamber and increasing themoisture content to 20- 24%.
After cooling and drying, the pellet density is typically
0.25- 0.3 g/ cm3
Production of floating pellets requires higher
temperatures and pressures than production ofcompressed pellets
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Feed manufacturing
Immediately after manufacturing, the pellets made bycompression pelleting are cooled and dried by passingthem through a cooler- dryer. Cool air is blown throughthe pellets, which are spread thinly on a moving belt in ahorizontal cooler. Passage through the cooler- dryer
takes 5- 15 minutes Extruded pellets contain more moisture than compressed
pellets and, therefore, need to be heated to reducemoisture to 10% or less. Drying takes approximately 30minutes
Crumbling and screening Dry pellets are crumbled by passing the cooled,
dried pellets through the corrugated rollers of acrumbler