Lecture 19 nutrition
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Lecture 19 nutrition

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    Lecture 19 nutrition Lecture 19 nutrition Presentation Transcript

    • Feed Ingredients and Physical Characteristics
    • 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/premixes mineral supplements/premixes growth/pigment enhancers ingredients improving palatability ingredients 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: brans rice 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
    • Non-nutrient Diet Components
    • 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
    • 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
    • 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
    • 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
    • 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
    • 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”
    • 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)
    • 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
    • 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
    • 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
    • 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!)
    • 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)
    • 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)