2. Formulating Feeds
• Nutritionally complete feeds should be used
whenever natural foods are absent or where
natural foods only make a small contribution to
nutrition
• when substantial amounts of natural
productivity are available, supplemental feeds
don’t need to contain all essential nutrients
• we will focus on nutritionally-complete feeds
3. Nutrient Requirements
• Most requirements for nutrients that have been
published focus on juvenile fish/shrimp
• many represent single lab experiments,
unchallenged, unsupported by others
• optimum performance can be affected by
management, environmental factors and
fish/shrimp size
• in formulating diets for a species for which
nutrient requirements are unknown, those for a
related species are used
4. Nutrient Requirements
• Most variation among aquatic species can be associated
with whether the animals are: 1) coldwater vs.
warmwater; 2) freshwater or marine; 3) finfish vs.
crustaceans
• values in nutrient requirement tables only represent
minima, don’t allow for processing or storage losses
• AA’s, minerals stable wrt heat, moisture, oxidation
• vitamins and lipids are not stable (affected by heat,
oxidation, light, moisture, etc.; store in cool area)
• 50% of ascorbic acid is lost in processing, half-life of 2-3
months in storage
5. Physical Properties
• Ground meals are not suitable
for feeding to aquatic animals
due to poor ingestion, feed
conversion, and reduced water
quality
• pellets need to be stable in
water until consumed by the
target animal
• good pellet stability required
for slow-feeding species such
as shrimp
• particle size is important to
insure appropriate consumption
various sizes of fish feed
particles
6. Physical Properties
• Diet texture is also important for some aquatic
species: some prefer moist vs. dry feeds (e.g.,
eels, salmon)
• sometimes farmers prefer floating pellets,
allowing confirmation of ingestion
• shrimp prefer sinking pellets (density greater than
that of water, 1 g/cm3)
• floating feed can be detrimental with respect to
consumption by competitors
7. Practical Feed Ingredients
• Ingredients used in practical fish/shrimp feeds can
be classified as:
protein sources (including amino acids)
energy sources (COH)
lipid sources (also essential fatty acids)
vitamin supplements/premixes
mineral supplements/premixes
growth/pigment enhancers
ingredients improving palatability
ingredients improving preservation/storage
8. Fish Meal (FM)
• If made from good quality whole
fish, properly processed, it is the
highest quality protein source
commonly available
• rich source also of energy and
minerals
• highly digestible, highly palatable,
also serves as an attractant
• usually contains about 65% protein,
that is around 80% digestible
• high in LYS, MET (deficient in
plant sources)
9. Fish Meal (FM)
• Fish meal also contains 1-2.5% n-6 fatty acids,
essential to many fish and all shrimp
• if made from byproducts, its quality is not as
good as trawler-caught
• only problem observed: high ash content can
sometimes result in mineral imbalance
• used sparingly because of high cost
• can be partially replaced by soybean meal and
other animal meals
10. Fish Meal (FM)
• When using FM, one must remember that it cannot be
stored forever
• can rancidify due to high lipid content
• further, not all FM is created equal
• some types (menhaden) appear to be superior to others
(sardine meal)
• FM must be very well ground and sieved to help
remove indigestible parts
• big producer countries are USA, Peru, Mexico,
Ecuador
11. Soybean Meal (SBM)
• Soybean meal has one of the
best essential amino acid
profiles of all protein-rich plant
feedstuffs
• Table 5.3 (Lovell)
• SBM does not appear to be
deficient in any EAA for catfish
• can be deficient wrt eel,
because their MET/CYS
requirement is twice that of
catfish
• some fish find SBM
unpalatable, for this reason
maximum levels are suggested
12.
13. Soybean Meal (SBM)
• Soybean meal is commonly
used to spare fish meal,
however, only to a point
• true for chinook, but not for
catfish
• shrimp will consume high SBM
feeds, but diet must be
supplemented with fish meal at
some point
• another problem involves losses
in energy, minerals and lipids in
diets where SBM replaces FM
or other animal byproduct
proteins
soy protein
14. Soybean Meal (SBM)
• Another variety of soybean meal is known as “de-
hulled”
• de-hulled soybean meal contains 25% less ME,
85% less available P and 90% less n-3 FA’s than
anchovy meal
• soybeans also contain trypsin-inhibitors
• trypsin inhibitor reduces digestibility of soy
protein by the enzyme trypsin
• solution: most soybeans are roasted prior to
milling (destroys inhibitor)
15. Full-fat Soybeans
• Full fat soybean meal is different from regular
SBM in that it has a full fat complement
• fat has not been solvent extracted
• 18% fat vs 0.5%
• often used as an energy source or for general
balancing of the formula
• mainly used in salmonid (cold water) fish diets
• REM: too high fat = reduced nutrient intake
16. Grains and By-products
• Grains are primarily used as COH sources
• when whole, they contribute about 62%-
72% of dietary starch
• starches are fairly well digested by warm-
water species (60-70%), but not by cold
• heating via extrusion improves digestibility
by 10=15%
• can also be used as binding agents
17. Grains and By-products
• Corn is commonly used in the U.S., but
is high in xanthophyll (a pigment),
giving tissue a yellow color (not good
for fish sales!)
• corn gluten meal is high in protein
(60%) and contains high levels of MET
(excellent for formulation)
• rice bran often used in developing
countries due to local rice production
• rice bran is a reasonable COH source,
but is high in fiber and fat
• wheat gluten is a good protein source,
but too expensive, often used as a binder
18. Animal By-products
• Meat and bone meal is a byproduct of
the slaughter house
• contains 50-55% crude protein
• protein quality is low, so only
marginally useful and varies dependent
upon meat source
• can be a good source of energy, P,
TM’s
• another problem: high ash content
• digestibility improved by flash- or
spray-drying
• poultry by-product meal (PBM) is often
used by mills also producing chicken
feed
• feather meal high in protein, but
indigestible
MM
MBM
19. Crustacean Meals
• Shrimp waste meal is a reasonably
good feed ingredient, if heads are
included
• otherwise, the shell is primarily chitin
and of limited digestibility
• the ammonia in chitin accounts for
about 10-15% of the nitrogen in
whole meal
• also a reasonable source of n-3 fatty
acids, cholestrerol and astaxanthin
(carotenoid)
• highly palatable and often serves as
an attractant in feeds at 1-2%
• others: krill meal, Artemia meal krill meal
20. Fats and Oils
• Used as energy sources, provide
essential fatty acids, attractant,
coating of pellet to reduce abrasion
• both animal and plant fats can be
used, animal fats cheaper, better
attractants
• marine lipids often added as oils if
FM level is low (otherwise no
source of marine FA’s)
• sources: menhaden, shark, cod
liver
• must be careful in storage of oil,
feeds with oils due to
rancidification
menhaden oil
21. Fibrous Feedstuffs
• Most monogastric animals (e.g.,
fish) do not digest fibrous
feedstuffs well
• it is unlikely that adding fiber to
diets already with more than 3-
5% will have any beneficial
effect
• high fiber content reduces
binding capacity of feeds,
inhibits intake (due to reduced
palatability), increases rate of
passage and waste production
• sources: brans
rice kernel
22. Binding Agents
• Binding agents are really needed for
pelletized feeds, but not necessarily for
extruded feeds (we discuss this later)
• in extruded feeds, all ingredients are
gelatinized by high temperature and bind
together well as a result of the process
• show Table 5.4 (Lovell, page 118)
23.
24. Binding Agents
• most organic binders are good for about 30
min of submergence
• starch is often used at over 10%, however it
will hydrate and swell the pellet
• chemical binders (e.g., Basfin) have good
binding potential, form cross-linkages with
COH and PRO, but are toxic
26. Basic Facts
• In addition to the essential nutrients, feeds may
contain organic and inorganic materials that have
various effects on aquatic species:
• beneficial, detrimental or negligible
• they can affect growth, health or the processed
product
• may be naturally occurring, intentionally or
unintentionally added
• can be produced via microbial growth
27. Toxins and Antimetabolites
• The more important toxins affecting animal feeding
are those associated with molds
• these are called “mycotoxins”
• three important genera are Aspergillus, Penicillium
and Fusarium
• they exist and grow anywhere as long as there is
enough COH substrate, no less than 14% moisture,
adequate temperature, oxygen
• usually produced in feedstuffs prior to harvest, but
also result from poor storage
28. Aflatoxin
• Aflatoxin is the mycotoxin of greatest concern in
feeding of culture species
• both outright toxic and carcinogenic
• liver (hepatoma) and blood clotting problems
• rainbow trout are highly sensitive at 1 ug/kg
exposure
• traditionally, sources include corn, cottonseed and
peanuts
• aflatoxin contamination varies year to year
29. Ochratoxin
• These are compounds produced by Aspergillus and
Penicillium molds
• widely found in nature
• typically associated with kidney toxicity
• toxic level is 4.7 mg/kg in diet
• other mold toxins have been found in warm-blooded
animals, but not in fish
• most mold toxins also destroy nutrients in feeds
• example: Pseudomonas can separate glutamic acid
from folic acid, making it ineffective
30. Microbial Toxins in
Commercial Fish/shrimp Feeds
• Usually not known that the feed is contaminated
• commercially-processed feeds are less likely to have
these toxins
• screened against international transport and by feed
manufacturers by law
• must contain less than 20 ppb
• up to manufacturer to require testing
• not destroyed by steam pelleting or extrusion
• presence in feeds reduced by proprionic acid
31. Histamine, etc.
• This is a toxic compound found in fish meal, a
typical feed ingredient
• results from bacterial removal of COOH
(carboxylic acid) from the EAA histidine
• comes from improper storage of raw fish prior to
production of fish meal
• causes a reduction in growth rate
• usually comes from “dark” meat portion of fish
• other fish meal toxin is “gizzerosine”
32. Phytic Acid, Gossypol
• Phytic acidPhytic acid is an organic molecule related to inositol
• integral component of plant feedstuffs and holds 60-
70% of the phosphorus
• problem is, it’s poorly available to fish
• reduces availability of zinc
• ““Gossypol”Gossypol” is a component of pigment lands in the
cotton plant
• limits availability of cottonseed meal used in feeds
(suppresses growth rate and causes liver damage)
33. Fish Oils, Fiber
• Marine fish oils contain 20-25% PUFA’s
• the “autoxidation” of PUFA’s results in formation of large
numbers of free radicals and peroxide compounds
• these are toxic due to reaction with other nutrients, limiting
availability
• also cause cellular/subcellular damage
• severity of effect reduced by Vit E
• fiber can also be mildly “toxic” as it increases rate of gut
passage
• high rate of passage causes reduced availability of nutrients
34. Diet Additives: Hormones
• Hormonal control used to produce mono sex
cultures of fish
• reduces reproduction/increases growth
• ex. Androgenic steroids (ethyltestosterone) fed to
tilapia fry = 90% males
• does not work the same on all fish
• 17-alpha-methyltestosterone improves growth and
survival in salmonids
• andorgenic better than estrogenic
• used as implants in cattle
35. Pellet Binders
• Steam pelleted aquatic feeds,
especially those fed to shrimp,
contain binders
• these are used for improving
water stability (reduced leaching
and nutrient loss)
• two different types: organic
matrix (lignosulfonates or
polysaccharides)
• other type: chemical compounds
(sodium hexametaphosphate)
• no evidence of detrimental effect
on aquaculture species
36.
37. Antibiotics
• Some feeds can be formulated with antibiotics
for treatment of Vibriosis, other bacterial
infections
• Three antibiotics approved in U.S. are
sulfadimethoxine, sulfamerazine and terrymycin
(oxytetracycline, OTC)
• OTC commerically available as “medicated” fish
(shrimp) feed, 1,500 mg/kg
• Must not feed medicated diets within 14-21 days
from slaughter/harvest (more regulations!)
38. Attractants
• Attractants are materials added to feeds to serve as
intake (feeding) stimulants
• They are cost effective since they cause shrimp/fish to
eat feeds that otherwise would not be attractive
(consumed)
• Facilitates inclusion of by-products
• Usual inclusion level is around 0.5-1.0 %, largely due to
cost
• Examples: krill meal, Artemia meal, fish oils, fish meal
• Sometimes used to reduce protein content of feed (but
most also feed more frequently)
39. Antioxidants
• Oxidation of lipids in feeds or feedstuffs can cause
reduction of the nutritional value of certain lipids
and vitamins
• It can also result in production of toxic free
radicals and peroxides (REM?)
• Potential for formation of these toxic compounds
reduced by synthetic compounds such as BHA
(butylated hydroxyanisole, BHT (butylated
hydroxytoluene)
• Also via natural compounds (Vit E)
