Feed Ingredients and Physical Characteristics

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Feed Ingredients and Physical Characteristics
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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 dont need to
  contain all essential nutrients
• we will focus on nutritionally-complete feeds

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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

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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, dont allow for processing or
  storage losses
• AAs, 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

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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
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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

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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

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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)

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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

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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

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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

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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
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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 FAs 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)

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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

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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
  1015
• can also be used as binding agents

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Grains and By-products

• Corn is commonly used in the U.S., but is high in
  xanthophyll (a pigment), giving tissue a yellow
  color
• corn gluten meal is high in protein (60) and
  contains high levels of MET
• 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

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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, TMs
• 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
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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
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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 FAs)
• sources menhaden, shark, cod liver
• must be careful in storage of oil, feeds with
  oils due to rancidification

menhaden oil
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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
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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)

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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

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Non-nutrient Diet Components
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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

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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

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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

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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

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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 all destroyed by steam pelleting/extrusion
  (spores)
• presence in feeds reduced by proprionic acid

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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

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Phytic Acid, Gossypol

• Phytic acid is an organic molecule related to
  inositol
• integral component of plant feedstuffs and holds
  60-70 of the phosphorus
• problem is, its poorly available to fish
• reduces availability of zinc
• 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)

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Fish Oils, Fiber

• Marine fish oils contain 20-25 PUFAs
• the autoxidation of PUFAs 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

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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

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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

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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)
• oxytet commerically available as medicated
  shrimp feed, 1,500 mg/kg
• must not feed medicated diets within 14-21 days
  from slaughter/harvest

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Attractants

• Attractants are materials added to feeds to serve
  as intake stimulants
• they are cost effective since they cause
  shrimp/fish to eat feeds that otherwise would not
  be attractive (consumed)
• allows 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)

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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)