Post on 14-Aug-2015
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
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
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
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
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
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/premixesmineral supplements/premixesgrowth/pigment enhancersingredients improving palatabilityingredients improving preservation/storage
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)
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
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
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
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
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)
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
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
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
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
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
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
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: bransrice kernel
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)
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
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