Topics to be covered

1
Feeds and Feed production (Chapter 9)

• Topics to be covered
• Introduction/types of feed
• Microalgae
• Zooplankton
• Feeding strategy
• Artificial diets (for larvae)
• Pond fertilization
• Compound feeds (for grow out)

2
Feeds and Feed production

• Feeds
• Feed is one of the major costs of aquaculture
  operations (30-60)
• Two types
• Hatchery feeds (typically live organisms)
• Nursery and grow out feeds (artificial
  formulations)

3
Feeds and Feed production

• Hatchery feeds
• Microalgae
• Zooplankton
• Rotifers
• Brine shrimp

4
Feeds and Feed production

• Microalgae
• Used as food source for,
• Larval, juvenile and adult bivalves
• Early larval stages for crustaceans
• Early larval stages for some fishes
• Zooplankton (food source for crustacean and fish
  larvae)
• Most often used microalgae include,
• Golden brown flagellates
• Green flagellates
• Diatoms (lack flagellum, non-motile)
• Culture methods
• Wells-Glancy method blooming of local species of
  phytoplankton in ponds or tanks containing
  filtered local water (to remove zooplankton while
  retaining phytoplankton)
• Inexpensive, but
• A bit unreliable (little control over which algae
  are grown uncertain nutritional value)
• Monospecific cultures with known starter material
  and controlled environmental conditions
• Better results than blooming methods, but
• Much more expensive require careful sterile
  procedures to avoid bacterial contamination and
  greater control over environmental conditions to
  enhance growth (Fig. 9.2-9.3)
• 4-phase growth (Fig. 9.4) harvest during log
  phase is best (optimal nutritional value)
• Batch, semi continuous, continuous culture systems

5
Feeds and Feed production

• Zooplankton Rotifers
• Culture of crustacean and fish larvae also relies
  on zooplankton feeds
• Rotifers are widely used (Small-type and
  Large-type)
• Whether the S-type or the L-type are used depends
  on the size of prey that the cultured organism
  can take in
• Females are larger than males and more common
• Under favorable conditions, reproduction occurs
  asexually and females predominate
• Under unfavorable conditions, reproduction occurs
  sexually and males are more numerous therefore,
  presence of males in rotifer cultures is bad news
• Rotifers are hardy and are easily mass produced
• Culture methods
• By inoculating a culture of microalgae with
  rotifers
• Population rapidly increases
• As microalgae are depleted, more is added to the
  culture
• A portion of the culture is usually removed on a
  daily basis and replaced with microalgae culture
• Bakers yeast can also be used with the algae as
  feed for rotifers
• Constant conditions are required for optimal
  rotifer cultures tank culture is best

6
Feeds and Feed production

• Zooplankton Brine shrimp
• Brine shrimp (Artemia spp.) are found worldwide
• Under favorable conditions, females produce
  free-swimming larvae (nauplii)
• Under unfavorable conditions, females produce
  embryos within a cyst, which are dormant
• Inactive (dry) cysts can be harvested and stored
  for many years
• When cysts are immersed in saline solution, cysts
  rehydrate, become spherical and embryogenesis
  resumes
• Cyst ruptures within 24 h and free swimming
  nauplius emerges
• Instar I 400-500 microns lacks digestive system
  and does not feed
• Instar II 12 h later begins to feed (e.g.,
  microalgae) and to grow in size
• Additional molting events occur (about 15 molts
  in total)
• Hatching of nauplii
• Best at 5 ppt salinity, constant light, 25-30 C,
  strong aeration, pH 8-9
• Harvest of nauplii
• Aeration is stopped and container illuminated on
  one side
• Empty cyst shells float to top
• Hatched nauplii swim toward light source
• Separation is easy and necessary to avoid
  problems (bacteria, disease, digestive problems
  caused by cysts)
• Alternatively, cysts can be decapsulated prior to
  incubation (by treatment of hydrated shells with
  hypochlorite solution)

7
Feeds and Feed production

• Zooplankton Brine shrimp
• If larger brine shrimp are desired, nauplii are
  reared in tanks for additional time
• Feed for brine shrimp growth is microalgae
• Growth conditions
• Good aeration
• Low light conditions
• 25-30 C
• 30-35 ppt salinity
• Good water quality and food supply

8
Feeds and Feed production

• Zooplankton Rotifers and brine shrimp
• Rotifers and brine shrimp are generally
  considered to be deficient in EFAs necessary for
  the growth of fish larvae, especially for marine
  fishes
• To overcome this problem, the EFA content of
  zooplankton needs to be manipulated using fatty
  acid enrichment techniques
• Zooplankton are fed certain microalgae, oil
  suspensions, microencapsulated diets and yeasts,
  and other preparations
• Similar enrichment techniques can be used to
  improve the zooplanktons content of vitamins

9
Feeds and Feed production

• Zooplankton Copepods
• Copepods exist in all aquatic systems and are
  natural prey for fish larvae
• Over 20,000 known species
• Planktonic forms range in size between 0.5 and
  2.5 mm
• There has been an effort to develop copepods as
  feed for fish larvae
• Results available suggest very good potential
• Nutritional value of copepods is better than
  rotifers and brine shrimp (higher levels of
  omega-3 HUFAs) but rotifers and brine shrimpe
  are used more often because at present they are
  easier to mass-culture.

10
Feeds and Feed production

• Zooplankton General feeding considerations
• As they grow in size larval fishes can be fed, in
  order rotifers, brine shrimp nauplii, larger
  brine shrimp
• Volume of live feed is determined according to
  the formula
• A (B x C)/D
• A required volume (L) of live feed culture to
  be fed to the larval fish
• B required density of live food in larval fish
  tank (number/mL)
• C volume of the larval fish tank (L)
• D density of the live feed culture (number/mL)
• It is important to monitor the presence of food
  in larval fish tank to prevent over or under
  feeding
• Disadvantages of live feeds
• Nutritional deficiency
• Nutritional inconsistency
• Reliability of supply
• Weaning from live organisms is accomplished by
  introducing formulated diets
• Efforts are underway to develop artificial feeds
  for fish larvae

11
Feeds and Feed production

• Artificial diets
• Advantages of artificial diets
• The size of food particle and its nutritional
  value can be adjusted to suit the target
  aquaculture species
• Nutritional consistency and off-the-shelf
  convenience
• But there are a number of criteria that must be
  satisfied (Table 9.7)
• Two types of microdiets are generally available
• Microbound diets
• Nutrients are bound within matrix (agar, gelatin,
  other)
• Prepared in form of slurry and then dried, ground
  and sieved to collect particles of defined size
• Potential problem is nutrient leaching into
  water
• Some success with fish larvae
• Microencapsulated diets
• Nutrients are enclosed within microcapsule wall
  or membrane
• Reduces problem of nutrient leaching
• Used to date primarily with bivalves and shrimp
  as co-feed with microalgae
• Success with fish larvae has been limited
• Total replacement of live feeds with artificial
  diet still not fully feasible for fishes

12
Feeds and Feed production

• Pond fertilization as food source for aquaculture
• Extensive and semi-intensive pond culture of
  herbivorous and omnivorous species is usually
  based on some degree of pond fertilization
• Pond fertilization is usually for the purpose of
  grow out, but it has also been used successfully
  for larval fish culture (e.g., for barramundi
  where pond culture of larvae has been successful)
• Fertilizers used may be inorganic or organic, or
  a combination

13
Feeds and Feed production

• Pond fertilization fertilizers used
• Inorganic
• Nitrogen ammonium sulfate
• Nitrogen and phosphate ammonium superphosphate
• Organic
• Animal manure
• Decomposed plant material

14
Feeds and Feed production

• Pond fertilization production in fertilized
  ponds
• Fertilization is to encourage primary
  (phytoplankton) productivity. Succession of
  organisms in the ponds include
• Bacteria and protozoan
• Plants phytoplankton, periphyton, macrophytes
• Animals invertebrates including zooplankton,
  zoobenthos, small nekton
• Not all ponds will yield the same composition or
  amount of plants and animals following
  fertilization
• Critical standing crop (critical fish biomass)
  maximum density (biomass) of a cultured fish
  population that can be maintained in the pond
  without a decline in growth rates (i.e., without
  a decline in natural feed availability in
  extensive/semi-intensive pond culture)
• Carrying capacity of a pond maximum density
  (biomass) of a cultured fish population that can
  be simply maintained, without further growth
• Fertilization increases the levels of both
  parameters
• Additional growth can only be achieved with
  supplementary feeds

15
Feeds and Feed production

• Compound feeds (grow out)
• Semi-intensive and intensive aquaculture require
  the use of artificial feeds, usually obtained
  commercially
• These feeds are primarily used to raise
  carnivorous and omnivorous fishes and
  crustaceans high-cost products in developed
  countries
• Artificial feeds started as larvae are weaned
  from live feeds
• Critical aspects of artificial feeds include
• Meet nutritional requirements of cultured species
• Lowest possible cost - least-cost formulation
• Feed composition tables include information such
  as (Table 9.9)
• Moisture (water content)
• Crude protein (total nitrogen content)
• Ether extract (lipid and lipid-soluble vitamin
  content)
• Crude fiber (cellulose)
• Nitrogen-free extract (carbohydrate content)
• Ash (inorganic content)
• Protein usually is the largest and most costly
  component of artificial feeds
• Square method is used to balance crude protein
  level (Fig. 9.9)

16
Feeds and Feed production

• Compound feeds - pellets
• Compressed pellets
• Grinding and mixing of coarse ingredients
• Compression of mixture under steam (85 C) and
  forcing mixture through holes in a metal die
  plate pellets of desired length are cut off as
  they emerge from die. Final moisture content
  after cooling off 10
• Pellet quality affected by lipid content usually
  should be 2-10
• Extruded pellets
• Dietary mixture exposed to high pressure and
  temperatures (125-150 C). Process causes water
  in mixture to evaporate leaving air spaces in the
  resulting pellets. Enables production of either
  floating or sinking pellets.
• Superior in nutritional value.
• Some drawbacks as well (Table 9.12)

17
Feeds and Feed production

• Compound feeds pellet storage
• Factors that affect pellet quality
• Age of feed
• Environmental factors such as
• Moisture of feed and humidity of storage area
• Temperature
• Light
• Oxygen
• Fungal contamination/insect infestation

18
Feeds and Feed production

• Compound feeds pellet storage
• Pellets will gradually equilibrate with
  atmospheric humidity. Cannot be stored in
  tropical climates for very long because of high
  humidity. Ideal moisture content for storage
  should be 10-12
• Oxygen causes rancidity of dietary fats and
  promotes growth of fungi and insects. Fungal
  damage is major concern in the tropics.
• Chemical changes that may occur during storage
• Oxidation of lipids and fermentation of
  carbohydrates
• Oxidation and fermentation may yield toxic
  chemicals and reduces the nutritional value and
  palatability of feed
• Use of antioxidants may help
• Loss of vitamins (especially vitamin C and B1)
• Can be compensated by coating or dipping pellets
  in vitamin rich material prior to use
• Loss of pigment color
• General rules
• Minimize storage time
• Protect from elements
• Keep storage area clean
• Refrigeration or air conditioning of storage area

19
Feeds and Feed production

• Compound feeds dispensing feeds
• Ration size species-specific feeding tables have
  been developed (Table 9.14)
• Feeding tables should be used as guide only
  amount adjusted by observation
• Methods of feeding
• Manual (hands, shovels, air-blowers)
• Feeders
• On-demand feeders
• Automatic (on timer, computer-controlled)