The Quest To Keep Salmon In The Pink Naturally

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The colour of farmed salmon has attracted so much attention within the aquaculture industry as it can be appreciated that the typical pink-reddish colour of salmon is symbolic of quality and value, with retailers demanding stringent criteria for farmed fish such as Atlantic salmon and trout to meet consumer expectations.
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  International Aquafeed is published five times a year by Perendale Publishers Ltd of the United Kingdom. All data is published in good faith, based on information received, and while every care is taken to prevent inaccuracies,the publishers accept no liability for any errors or omissions or for the consequences of action taken on the basis of information published.©Copyright 2012 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any formor by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058 March | April 2012Feature title: The Quest To Keep Salmon In The Pink Naturally The International magazine for the aquaculture feed industry  T hecolouroffarmedsalmonhasattractedsomuchattentionwithintheaquacultureindustryasitcanbeappreciatedthatthetypicalpink-reddishcolourofsalmonissymbolicofqualityandvalue,withretailersdemandingstringentcriteriaforfarmedfishsuchasAtlanticsalmonandtrouttomeetconsumerexpectations. Indeedthishasoftenprovedcontrover-sialinthemediawhenthefarmingoffishhasbeencriticisedonmanygroundswithnegativestatementsalludingtotheuseofsyn- theticagentsandevendyessuggestedasthesourceofartificialcoloursbeingprominentlyexpressedbythemisinformed.Carotenoidscompriseacomplexgroupofxanthophyllsandcarotenes,whicharediverseintheirchemicalstructuretoprovidethehostofyellowtoorangered,andpinkcoloursfoundextensivelyinnatureasalsoseenintheplumageofbirdssuchasflamingos.Themaincarotenoidsofimportancetosalmonand troutareastaxanthinandcan- thaxanthin,whicharespecificintheirmodeofactivityandintheirmannerofmetabolism.Astaxanthinisrecognisedtobe thepredominantredcarotenoidfoundinsalmonidsinnaturewithcanthaxanthinalsousedcommerciallytoamorelimitedextent. A dietary requirement Salmonandtroutdonotpossesstheinherentmetabolicabilitytosynthesisethesepigmentsbutinsteadrequirethemwithin thedietaspreformedmoleculesthatareabsorbedandsubsequentlydepositedintis-sues(Bjerkeng,2000).Itshouldalsobenotedthatpigmentationleadingtothereddish-pinkandorangecolourofintegumentisalsofavouredforcertainfish thatcandepositcarotenoidsormetabolicderivativesintheskinsuchasredseabreamandredtilapia(Gouveiaetal,2002).Thisisalsoacharacteristicofhighvalueandaccept-abilitytoconsumerswhoperceivethistobesuperiorcomparedtoun-pigmentedfish.Theefficacyoffleshcolourationbydif-ferentcarotenoidsisafunctionofcomplexphysiologicalprocessesfollowedbyaseriesofbiochemicaleventsthatinvolvemetabolismprimarilyintheliveraswellastheintestinal tract(Pageetal2005,PageandDavies,2006).EvidencefromtheresearchinvestigationsofWhiteetal(2003a)suggeststhatamajorfractionofabsorbedastaxanthinistrans-formedintovitaminAintheintestinaltissueofrainbowtroutandmostlikelysalmonaswell.Inadditionthereisincreasingevidence thatcarotenoidsareinvolvedingeneregula- tionandsignaltransductiontherebyaffecting theentiremetabolismoffish(Azzi,2007;Lordanetal2008).Theyarealsopotentanti-oxidantsthatcaninteractwithvitaminE( α-  tocopherol)andcanpreventfattyacidoxidationduetofreeradicalgenerationwithin tissues.Therearealsopositivebenefitsonthepostmortemqualityoffishunderfrozenstor-ageconditionswhenfedhighlevelsofcaro- tenoidsthusprolongingshelflifeofproducts(Jacobsenetal(2011).Inthiswayastaxanthinandcanthaxanthinhavepro-vitaminandmet-abolicfunctionswellbeyondtheirstandardroleforpigmentationandcouldthereforebeviewedasconditionallyessentialnutrientsforsalmonidfishspecies.Davies(2005)previouslyreviewedsev-eralaspectsofbiochemicalandphysiologicalparametersaffectingsalmonidpigmentationwithparticularemphasisonpost-prandialabsorptionkineticsandretentionefficiencyandexplainedthatconsiderableamountsofastaxanthinandcanthaxanthinisexcretedbyfishandthereforeefficiencyofutilisationisquitelow(~20percent)comparedtoothernutrientssuchasproteins,aminoacids,vita-minsandminerals.Therearemanyproductionrelatedfactors thatcaninfluencethedegreeofpigmentationoffarmedsalmonids.Theseincludespecies,raceorstocktype,intra-populationvariation,ageoffish,typeandquantityofcarotenoidsingestedoverspecificperiod,seasonaleffects,maturation,healthandstateofphysiologicalstress,dietaryformulation,regulatedfeeddep-rivationperiodsmaintenancefeeding,slaughterconditions,visualisationofcolour,processingconditions:storage,smoking,cookingetc.Thehighgrowthratesachievedinmodernsalmonproductioncanresultinareductionofpigmentationandunevendistributionwithin theflesh.Itiswellknownthatconsiderablevariationscanoccurintheabilityoffishtoretaincarotenoidswithinthemuscleandthiscansometimesmanifestasverylowpigmen- tationorindeedexcessivelevelsindifferentregionsofmuscle.Indeedthefactthatseasonalchangescan The quest to keepSalmon in the pink naturally   by Simon J Davies, School of Biosciences, Plymouth UniversityEngland, UK 16 | IntentIon AquAFeed | March-pril 2012 FEATURE   modulatevariousselectedmusclequalityparameters,includingthedegreeofpigmenta- tioninsalmonwasnotedbyNordgardenetal.(2003).Theseinvestigatorsconcluded thatrapidperiodofgrowthachievedundercontinuouslightingcomparedtonaturalphotoperiodresultedinelevatedgrowthofsalmonandincreasedoxidativestresswithmarkedreductionsinfilletvitaminElevels(a-tocopherol)andastaxanthin. Environmental factors Otherenvironmentalfactorsthatmayaffecttheefficiencyofpigmentationwouldlikelyincludewaterqualityandflowratesthatwouldinteracttomodulategrowthandnutri-entretention.Stockingdensityandexerciseareknowntoaffectfishperformanceandoptimumfishstockingdensitieswillproducesuperiorgrowthandfeedconversionleading toimprovedfishquality.Similarly,adequateflowrates,waterexchangerateswillpromotefirmerfleshedfishandmayenhancepigmentationinfishunderintensiveproductionsystemsasdescribedpreviouslyinrelationtomusclequality.ColourationanditsrelationshiptofleshqualityinfarmedtroutandsalmonwasextensivelyreviewedbyDavies(2008)whichaddressedcarotenoidfunctioninfishaswellasthephysiological,biochemicalaspectsandaestheticattributesleading towardsoptimalpigmentationofsalmonidfish.Ourknowledgeoffishnutritionhasexpandedconsiderablyinrecenttimesand therehavebeennumerousinvestigationsthathaveaddressedtheeffectsofdietarylevelsofbothastaxanthin,canthaxanthinseparatelyorincombinationonthefleshcolourationof troutandsalmon.Thetypeoffeed,leveloffeedingandmatrixeffectsoncarotenoiduptakewillaffect thedegreeofpigmentationinandcansignifi-cantlyalterthecolourcharacteristicsresultinginpossibletaintingwithbackgroundcolour.Anoptimumdietarylevelofabout65-mg/kgastaxanthinispreferableingeneraltoachieveacceptableresults.Aminimumsize thresholdexiststoinitiatepigmentationinsalmonandtroutandmaintaindepositionduringtheinitialfreshwaterstagesofgrowthinfishofabove80-100gramsmeanbodyweight.Thisextendswithsubsequenttransferassmoltstoseawaterwithsalmontypicallyfed65mg/kgtotalcarotenoidseitherasastax-anthinorincombinationwithcanthaxanthinwiththelatternotexceeding25mg/kginthemixture(EUdirectives).MaximumpermittedlevelsforastaxanthinintheUSAis80mg/kgoffeed(FDA,2010).However,revisionofsuchlevelsisthebasisofmuchscientificactivitytooptimise theiruseandminimisewastageandcost.Overthelastdecade,feedmanufactur-ershavebeenabletosignificantlylowertheinclusionofpigmentinfeed.Instead,itisrec-ommendedbysome,thatathree-phasepig-mentationstrategywithpost-smoltsbeingfedpigmentatarelativelyhighlevelof60-75mg/kgwithatransitiontoanintermediatelevelof40-50mg/kgfromabodyweightof2-3kgbeforeafinalregimemaintainedonafinishingdietpriortoharvestof25-35mg/kgofdietarycarotenoidsconcentration(Sinnot,2006).Therearesomescientificrationalesforsupportinghigherdietpigmentlevelsinthelaterstagesofgrowthforthefeedingoflargeadultfish.Thisisbasedontheviewthatlargersalmoncanpigmentmoreefficientlythansmallerfish.Sincepigmentationdevelopsquiterapidlyfrompost-seawatertransfer,pigmen- tationrategenerallyslowsdownwhenfishgetbiggeralthoughtheabsorptiveefficiencymayactuallyincrease.Itisstillthereforewisetopromoteastrat-egybasedonusinghigherlevelsinearlyphasefeedingwithareductiontoamaintenancelevelinfishapproachingharvest. The impact of plant oilson pigmentation Choubertetal(2006)havereportedthat thepigmentingefficacyofastaxanthinfedtorainbowtroutwasaffectedbythecomposi- tionofdietaryoilpresent.Someevidencesuggestsreducedpigmen- tationefficiencymayresultinfishfeddietswithelevatedplantoilsoverextendedperi-odsduringgrowth.However,consumertestsseemtoindicate thattherearenosignificantdifferencesinpub-licperceptionregardingtheoverallappear-anceofsalmoncolourwhenfeddietregimes thatincludeappreciablelevelsofvegetableoilsourcestoreplacefishoils(Rosenlundetal.2003).Thisisofimportancegiventhetrendofusinghigheramountsofplantoilblendsforamajorpartoftheproductionandthestrategyofusing‘fishoil’enhanced‘washout’dietsinthefinalstagetoharvesttoachievehighomega3fattyacidconcentrationsin thefleshofsalmonpriortomarket.Quintonetal(2005)conductedtrialswithsalmontoascertaintheinfluencethatgeneticscanplayinaffectingtheabsorptionofdietarycarote-noids,metabolismandtheefficiencyoffleshdeposition.TheseworkersinCanadaevaluatedthegeneticparametersindifferentyearclassesofAtlanticsalmonreachingharvest.Theydeterminedsexualmaturationchar-acteristicsandassociationstocolourscore,astaxanthin,canthaxanthin,oil,andmoisturecontentsofflesh.Positivegeneticcorrelationswerefoundbetweenbodyweightandwithpigmentretentionlevels.Obviously,thereisthescopetoexploitmoreefficientstocksfortheirpigmentationcapacityusingselectivebreedingprograms.Suchfindingscouldresultinmoreevenandconsistentfleshcolourforsalmonandtroutandtailoredtodifferentproductionsystems. Less intensive conditionsfor farmed fish Traditionaluseofcommerciallysyntheticsourcesofastaxanthinincompoundedfeedsaddsgreatlytotheircostsandthevalueoftheresultingproducts.Theannualsalesofsyntheticastaxanthinforaquaculturealonewereestimatedatmore thanUS$200millionat2010.  March-pril 2012 | IntentIon AquAFeed | 17 FEATURE Extruder OEE for the Production of Fish FeedExtruder OEE for the Production of Fish Feed  AMANDUS KAHL GmbH & Co. KG, Dieselstrasse 5-9, D-21465 Reinbek / Hamburg, Phone: +49 40 727 71 0, Fax: +49 40 727 71 100info@amandus-kahl-group.de, www.akahl.de  Recently,however,therehasbeenagrow-ingdemandintheproductionoffarmedfishunderlessintensiveconditions,andwithmoreemphasisonnaturaladditivesandsup-plementsinthediet.Assuch,anumberofinvestigationshavereportedthefeasibilityofvarioussinglecellproductssuchastheredyeastPhaffiarhodozymaandHaematococcuspluvialisalgaewithrespecttotheirpigmenta- tionabilitycomparedtothesyntheticformcurrentlyavailabletotheindustry(Lagocki,2001).InvestigationshaveconfirmedthatPhaffiacaneffectivelypigmentsalmonidfishbutonlyfewproductsarecurrentlyavailableforthispurpose.Choubertetal(2006)founddiffer-enceswithrespecttothecolourofrainbow troutfedHaematococcuspluvialiscompared tosyntheticastaxanthinwithhigherreportedcolourandfleshretention.Theprevailingconsensushasbeenthat thesyntheticcommercialastaxanthinisread-ilyavailableforassimilationbyfish,andisamorestableandconsistentproduct.Itshouldalsobenotedthattheastax-anthinpresentinHpluvialisisfoundascomplexesterswhichconferdifferentassimi-lationpropertiescomparedtoothersourcesaddingtovariableresultsunderpracticalconditions(Bowenetal,2002;Whiteetal,2003b),thereiscurrentinterestinseaweedsandextractsfrommacro-algaewhichcancontainappreciablelevelsofcarotenoidsaswellaswasteproductsfromkrillandshrimpprocessing.However,thesematerialsareinconsist-entinavailabilityandcarotenoidlevelsmayvarywithseasonality.However,specialityseaweedsmayhaveapromisingfutureasfeedadditivescombiningfunctionalityasprebioticsandcontributingtonaturalcaro- tenoidintake. Algal and yeast sources Despitethepotentialofbothalgalandyeastsourcesofcarotenoidsbeingabletoeffectivelypigmentsalmonandtrout,thesehavebeenprohibitiveintermsoftheirconsiderablecostsandvariablequalitiescomparedtosyntheticproductswithconsist-entcharacteristics.Consequently,anexcitingdevelopmentistheproductPanaferd-AX®producedbyaleadingJapanesecompanyNipponOilCorporation.Panaferd-AX®containsthedessicatedcellsofParacoccuscarotinifaciens,asoil-inhabitingbacteriumwhichnaturallycontainscarotenoids.Thebacteriaareculturedbyfermentationandhavebeenselectedtoyieldhighcaro- tenoidconcentrationswithouttheneedforgeneticmodification.Althoughastaxanthinis themajorpigmentwithinPanaferd-AX®,itcanalsoexpressappreciablelevelsofnaturaladonirubinandcanthaxanthin.Bothofthesecarotenoidscanalsosupportadditionalpig-mentation tofishthatdeposit theseinmuscleandskin.Theredcarotenoid-richbacte-riumParacoccuscarotinifaciensispermittedasasensitiveaddi- tiveforuseinsalmonandtroutwithamaximumcontentof100mg,expressedasthesumofastaxanthin,adonirubinandcanthaxanthinperkgcompletefeed.Thecurrentcarotenoidcompositionoftheproductisspecifiedas3–5gcanthaxanthin,10–15gadonirubinand20–23gastaxan- thin/kg.Theapplicantproposestomodify therangesofcanthaxanthinto1–5g,and thatofadonirubinto7–15g/kgproduct,whilemaintainingtheastaxanthinrange.TheEuropeanFoodSafetyAuthority(EFSA)oftheEuropeanCommissionhasexpertlyreviewedthetermsofauthorisationoftheproductforfishandverifieditsefficacyandsafety.IndeedanumberoftrialsinScotlandbyleadingfeedmanufacturer’sandsalmonproducershaveprovedmostencouragingwithfavourableresultsobtainedinproduc- tioncages.Fleshpigmentdepositionandstabilitycomparabletothatofsyntheticpigmentationregimesprovedacceptableandquitecompa-rablewithorthodoxproducts.ThefeedbackreceivedsofaronfishpigmentedwithPanaferd-AX®hasbeenconsistentlygoodfromtheretailerandconsumerstandpoint. Tohaveallthecolourinoursalmonderivedfromnaturallyoccurringorganismsis theculminationofyearsofhardwork, saidmanagingdirectorNickJoyofLochDuartsalmoninScotlandwhohavebeenpioneer-ingtheproductintheirbespokenfeeds. Asafarmer,Iamproudthatwerearwell-nourishedsalmonthatlookandtastegreat, hehasstated. Consumers and retailersare driving the agenda ItseemsthatPanaferd®willbenefitsalmonproducersgloballybyofferingoppor- tunitiesfordiversificationinthemarketplace.SincetheproducthasfullFDAandEUapprovalforuseandisavailableforapplica- tionintheindustryit’slikelytobeusedincreasinglyinmain-streamproduction.Itistherequirementsoftheconsumerandretailersthataredrivingtheagendaandgeneratingtheneedformoreinformationin thisareawithmediaattentiontocolourationoffarmedfishandcrustaceanspecies.Thequestionofproducinga‘pink/red’fleshedsalmonin thesamemannerasawildsalmonaccumu-latespigmentisawidelyacceptedprincipleadvocatedbyanumberofmarketsurveysinwhichthepinkfleshcolourofsalmonscoresconsistentlyhigherasadesirablefac- torsecondonlytofishfreshness(Baker,andGünther,2004)Intermsoffeedcostsitiswellknown thattheaddedcostsofincludingastaxanthininfeedsamountstoanextra10-15percent,whichmanifestsasanadditional4-6penceperkilogramproduced,thatisacostofUK£40,000-UK£60,000per1000tonnesofproduction.InEurope,itiscommonpracticetopig-mentrainbowtrouttoadefinedlevelatpor- tionsizealthoughthisisnotsousualintheUnitedStateswhereun-pigmented(white)fleshedrainbowtroutismorefavouredby theconsumer.Severalfeedcompanieshaveevaluatedthecostsofpigmentingrainbow trouttowardsharvestwithstrategiesformoreeconomicapproachesadvocatedbyseveralfeedcompaniesandfishfarmingoperations. Colouration is an emotive issue Thequestionoffishcolourationinfarmedaquaticspecieswillalwaysbeanemotiveissuesinceitiseasilyvisualisedandcanbemeasuredbysuitabletechniquesrangingformdirectchemicalanalysisinfeedsandfleshorbyaselectionofopticalmethodsbasedoncolourscaleassessmentsandadvancedimageanalysis.Theaquafeedindustryandfishnutritionistmustberesponsiveandembracetheoppor- tunitiesforinnovativeproductsincludingnaturalpigmentingagents.Withtheneed toconsider‘organic’certificationforfarmedfishandthequestforsustainableingredients,researchisneededtoevaluatetheefficacyofcarotenoidsfromawidespectrumofpotentialsources.Thiswillbeacontinuouschallengeasfeedformulationsbecomerefinedandasnewcandidatespeciesbecomeavailableforaquaculture. ■ Referencesavailableonrequest 18 | IntentIon AquAFeed | March-pril 2012   FEATURE    www.aquafeed.co.uk  LINKS ãSeethefullissue ãVisittheInternationalAquafeedwebsiteãContacttheInternationalAquafeedTeamãSubscribetoInternationalAquafeed Volume 15 Issue 2 2012 the internationalmagazine for the aquaculture feed industry  Filtrationinrecirculationparticle controlFishProteinHydrolysates  – FPH enhanceresistanceofaquaculturespecies todifferent types ofstress The quest tokeep Salmoninthe pink naturallyAquaculture development inSub-SaharanAfrica Thisdigitalre-printispartoftheMarch|April2012editionofInternationalAquafeedmagazine.Contentfromthemagazineisavailabletoviewfree-of-charge,bothasafullonlinemagazineonourwebsite,andasanarchiveofindividualfeaturesonthedocstocwebsite.Pleaseclickheretoviewourotherpublicationsonwww.docstoc.com.Topurchaseapapercopyofthemagazine,ortosubscribetothepapereditionpleasecontactourCirculationandSubscriptionsManageronthelinkabove.INFORMATIONFORADVERTISERS-CLICKHERE
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