March | April 2013

Towards aquafeeds with increased food security

The International magazine for the aquaculture feed industry

International Aquafeed is published six 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 2013 Perendale Publishers Ltd. All rights reserved. No part of this publication may be reproduced in any form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058

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36 | InternAtIonAl AquAFeed | March-April 2013

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From both nutritionist and aqua-culturist points of view, our aimis to sustainably produce aquaticfoodwithsuperiorsensoryproper-

ties and high cardioprotective properties.The reason is that although preventable,cardiovascular diseases (CVDs) remain thetop global cause of death and stroke.Thepreventionofatherosclerosisis,therefore,amajorobjectiveofmodernmedicalandbio-chemical investigations into the mechanismof atherosclerosis and how the structureof food components determines their roleinthemechanism(s) involved.Thecomposi-tion of aquafeeds and their impact on thenutritional value of aquatic food is a focalpoint of today’s research and developmentbothinacademiaandindustry.

Since the study of the seven countries(Keys et al., 1984), some unanswered ques-tionsstillremainastowhycohortsinGreeceand Italy had coronary heart disease (CHD)at low frequencies but high levels of serumcholesterol(Figure1).

Thereiscompellingliteratureontheben-eficial role of omega-3 polyunsaturated fattyacids (omega-3 PUFAs) and there is a corebeliefthat fish isgoodforourheartbecauseof thesePUFAs.Mechanistically, though, it isnot clear how omega-3 PUFAs work. Their

postulated mechanism in preventing athero-sclerosis could be through lowering the lev-els of triacylglycerol, preventing arrhythmias,decreasing platelet aggregation or loweringbloodpressure(Saravananet al.,2010).

On the other hand, the association ofomega-3PUFAsandCVDshasbeenrevisedrecentlybyevaluatingallrandomizedtrialsonthe supplementation of omega-3 PUFAs toadults (Rizoset al.,2012). In this review, theresultsof20studieson68,680patientswereevaluated and omega-3 PUFAs were notfoundtobestatisticallysignificantlyassociatedwithCVDs in variouspatientpopulations. Inthe light of this study, we may need to re-focus our research quests towards feed andfoodcomponentswithprovedcardioprotec-tiveactivities.

Polar lipids of fishLipid microconstituents of specific food

that constitute important ingredients of theMediterranean Diet have been found thattheyhavein vitro(inthetesttube)importantcardioprotectiveproperties (by inhibiting theactions of the so called Platelet ActivatingFactor,PAF).PAF is themostpotent inflam-matorylipidmediator,awell-recognizedago-nistofplateletaggregationthatplaysacrucialrole in atherosclerosis, i.e. the developmentofcardiovasculardiseases.These lipidmicro-

constituents can practically inhibit the onsetof atherosclerosis and the development ofCVDs(Zabetakiset al.,2013).Suchlipidshavebeen found inawide rangeof foodsuchasredandwhitewine,yoghurt,fish,oliveoilandolive pomace. Further in vivo (using rabbits)studies of olive oil, olive pomace and aqua-cultured fish (Nasopoulouet al., 2010) havere-confirmedthat it is thepolar lipid fractionof these food sources that can reduce thethicknessofatheroscleroticlesionsinhyperc-holesterolaemicrabbits(Figure2).

In a further mechanistic study, our grouphas recently demonstrated that the polarlipidsofseabreamhavedown-regulatedPAFbiosynthesisandup-regulatedPAFcatabolism;practically the polar lipids of fish can inhibitatherosclerosis related enzymatic activities

(Nasopoulouet al.,2011b).

Heavy dependency on fish oilsThe steadily increasing population on

Earth makes the sustainable production offoodoneofthemajornutritionalproblemsfor mankind to address. In terms of foodsecurity in aquaculture, we need to facesuccessfully a ‘paradox’ on the sustainableproductionoffishfeed:today,highamountsoffishoil(FO)arerequiredtoproducefishfeed.Currently,40percentand60percentoftheglobalproductionoffishmealandfishoil, respectively, are used in aquaculture.Salmonid diets alone consumed over 55

percent of the fish oil used by the aquacul-ture sector in 2006. About 50 percent ofworldmarine fish stocks have recently beenestimated as fully exploited, 32 percent asoverexploitedandonly15percentasunder-exploited. These exploitation data suggestthat the diminishing levels of available wildfish worldwide combined with the fact thataquaculturedcarnivorousspeciesrequirelargeamounts of wild fish in their feed create anemerging necessity to improveour resourcemanagementpractices.

Towards aquafeeds with increased food securityby Ioannis Zabetakis, assistant professor of food chemistry, University of Athens, Greece

Figure 1: Rate of mortality due to Coronary Heart Disease (CHD) per quartile of serum cholesterol in pooled cohorts of the Seven Countries Study (adopted from de Lorgeril M et al. Cardiovasc Res 2002;54:503-515)

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Need for novel sources

In order to reducedependence on fish oil, sig-nificant breakthroughs have

occurred over the past fewyearsinreplacingitwithplantoils.Bysubstitutingfeedswith

plantoils,italsoservestoreducecostsduetothefactthatvegeta-

bleoilshavesteadilyincreasingproduc-tion, high availability and better economicvalue.Several studieshavebeencarriedout

toinvestigatecertainvegetableoilsaspos-siblesustainablepartialsubstitutesforfishoils incompoundedfish feeds.Themost

commonvegetableoilsusedforfishfeedpro-ductionhavebeensoybean,linseed,rapeseed,sunflower,palmoilandoliveoil.

Soybeanand rapeseedoil areconsideredpossible alternative lipid sources for salmo-nids, freshwater and marine fish since theyare rich in PUFAs, especially linoleic (18:2ω−6)andoleicacid(18:1ω−9),butdevoidof n-3 PUFA. However, in some cases, fishoil substitution by 60 percent rapeseed oilhas been found to decrease European seabass (Dicentrarchus labrax) growth. Soybeanoil appears to be a better plant lipid sourceregarding gilthead seabream (Sparus aurata)growth while considerable savings in feedcostscouldbeachievedifitcouldbeusedas

a partial dietary substitute for fish oil withincompoundfeeds.Thesameistrueoflinseedoil and rapeseed oil, although to a lesserextent.

Furthermore,theuseofpalmoilindietsofAtlantic salmonand rainbow trouthas given

growthandfeedutilizationefficiencycompa-rabletofishfedwithequivalent levelsof fishoil. Olive oil could also be used as a partialsubstitute for dietary fish oil in Europeansea bass culture, during growth out phase,Atlantic salmon (salmo salar) and rainbowtrout(Oncorhynchus mykiss)withdatashowingsimilargrowthratestotheoneswhenfishwasfedon100percentfishoildiet.Allthesestud-

ieshavebeenrecentlyreviewed(NasopoulouandZabetakis,2012).

New, alternative and in a way ‘non-orthodox’, sources of lipids need to beidentified and valorised in order to achievesustainableproductionof fish feedsand thus

enablingthefurtherdevelopmentofaquacul-tureapplications.Suchpromisinglipidsourcesarevegetableoils(VO).TheuseofVObasedaquafeedshassomestrongadvantages.Olivepomace (OP) and olive pomace oil (OPO)are natural by-products of olive oil produc-tion, which contain micro constituents withatheroprotective(substances)activitysuchasPAF-inhibitorsandphenolic/polyphenolicmol-

Figure 2: Representative optic micrographs x 100 of aortic wall sections stained with haematoxylin and eosin from the two experimental groups, where atherosclerotic

lesions appear as foam cells (↑). (A) Group A (atherogenic diet); (B) Group B (atherogenic diet enriched with sea bream polar lipids) (adopted from Nasopoulou et

al., 2010). Copyright, “Food Chemistry” Elsevier

B)

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AquacultureEscapesCommission(AEC)intro-ducedanotificationtemplatefiveyearsago.

Placing responsibility on suppliersTwoproblemareasstandoutintheefforts

to reduce the risk of escapes in Norwegianaquaculture. Jensen believes that both canbe solved by the suppliers of aquacultureequipment.

“If the aquaculture industry is ever goingtorealisticallyrealiseitsvisionofzeroescapesfrom sea-based production facilities, it mustsolve two big challenges. The first is thatweightingsystemscurrentlyinusetomaintainthe shape and volume of the net pens leadtowearand tear in thenetting.The secondis finding ways to decrease the incidence ofoperational–orhuman–error.”

Solutions can be developedDr Jensen points out that the key to

solving both challenges can be found in thesupplierindustry.

“Improvedproductdesignandprocedurescanmitigateand, inpart,preventbothwearandtearaswellashumanerrorduringopera-tionsatsea.Muchoftheequipmentinuseinsea-based facilities shouldbe redesignedandsimplifiedtomakeitdifficultorimpossibletouse incorrectly. Under the SECURE projectwehaveacquired theknowledgeneeded todevelop better and more secure solutions.Thenextstepisuptothesuppliers.”

Suppliers have already begun applyingthe documented findings from the SECUREproject to test new solutions. The ResearchCouncilofNorwayallocated funding to twonewresearchprojectsthisyear(Towardssus-tainable fish farming at exposedmarine sites[SUSTAINFARMEX2011-2014]andExposedFarming)thathavecarriedoutmodellingtestsusingnetswithintegratedsinkertubes.

Certification scheme improves safety

The SECURE project has documented anumberof factorssignificant foravoidingnetabrasionandtearing:

• Insufficient weighting of net-cages, useof exceedingly large nets, sea-currentconditions and biofouling lead to netdeformation and risk of abrasion andtearing.

• Washing nets by machine reduces thestrengthofnetthreadsby10-20percentafter4-5washings.

• Attachingthesinkertubetothenethasproven to be a more secure solutionthanusingslidingconnectors.

• Conic net pens create more distancebetweenthenetandthechain,reducingtheriskofabrasionandtearing.Inspiteof this, the majority of net pens arecurrentlycylindricalinshape.

“Fish producers are able to buy freely

on the market and can purchase nets andfloating collars separately. It is by no meansautomatic that the net chosen will suit theselected floating collarwhenassembled.Weneedtohaveamoreintegratedapproachtothe design of fish-farming systems to ensurethatcomponentsarecompatible,”explainsDrJensen,whobelievestheintroductionoffacil-itycertificationisastepintherightdirection.

Providing input for regulations

Asof January1, 2013, all fish-productionfacili-ties in Norwaymust have cer-tification statingthatthefacilityisusingcompatiblecomponents.

“TheSECUREprojecthas providedknowledge ofimportance tothe design ofregulations thatthat will formthe basis forfacility certifica-tion, amongother things.We have seenthat the layoutofafacilitycom-binedwithwavesize can haveunforeseen con-sequences. Thehighest wave

doesnotalwayscarrythegreatestforce.Wehave found examples where a low-crestedwaveexertsmuchgreater forceona facilitythan a steep wave. Twice the force is notunusual,andthisshouldobviouslybeincorpo-ratedintothespecificationsforthedesignanddimensions of a production facility,” Jensenconcludes.

More information: www.forskningsradet.no

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FEATURE

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eculeswithantioxidantandotherpleiotropicactions. Extensive research has been carriedby our team on olive oil by-products andfish with regard to their capacity to preventatherogenesis.

Recently,thepossibilityofpartiallyreplac-ingfishoilingiltheadseabreamandseabassgrow-outdietbylipidsobtainedfromOPandolivepomaceoil (OPO)hasbeen reported.Inactualfact,thefeedingofOPtofishresultsin an improvement in its ability to preventatherosclerosis and therefore cardiovasculardiseases(Nasopoulouet al.,2011a).

GM plants There have been numerous studies on

genetically modifying the plant oil profile sotheplants increase thebiosynthesisofeitherthe precursors of omega-3 and omega-6fatty acids or these fatty acids themselves.These modifications have focused on C 18Δ6-desaturatedfattyacids(suchasγ-linolenicand stearidonic acid), omega-6- long-chainPUFAs(suchasarachidonicacid)andomega-3-long-chain PUFAS (often referred to as‘fishoils’) (such as EPA andDHA) and theyhave been recently revised (Haslam et al.,2012). The research approach is based onthe assumption that omega-3 and omega-6PUFAs have considerable nutritional valueand thus efforts have focused in enhancingthe bioformation of these molecules in the‘designer’oils(aftergeneticmodification).

However, under the light of recent evi-dence that omega PUFAs have less nutri-tionalvaluethatpreviouslyconsidered(Rizoset al., 2012), these genetically engineering

approaches need to be carefully considered.Scientifically, we need to assess any relatedenvironmental impact when GM plants arecultivated and commercially, we need toaddressthepublicconcernsandneedoftheconsumers (at least in EU) for ‘GMO free’food.

Food for thought / future actionsIn today’s rapidly changing world, we

are asked to face conflicting problems andissues such as the overproduction andwaste of food, obesity, CVDs and diabetesin the developed countries, famine andmalnutrition in the developing countries,climate change, scarcity of water, rationaluseofcultivatedlandandsustainableuseofresources and energy. In this complex andswiftly changing environment, the issue offood security and on how we can securenutrition for the entire human populationbecomes a top priority for all of us inthe feed and food arena.The sustainableproductionof food isacomplexchallenge.Some insights inapproachingthischallengehavebeenhighlightedwiththisar ticle. ■

ReferencesHaslamRP,Ruiz-LopezN,EastmondP,MoloneyM,SayanovaO,NapierJA.2012.Themodificationofplantoilcompositionviametabolicengineering-betternutritionbydesign.PlantBiotechJournal2012:1-12.

KeysA,MenottiA,AravanisC,et al.1984.TheSevenCountriesStudy:2,289deathsin15years.PrevMed13(2):141-54.

NasopoulouC,KarantonisHC,PerreaDN,TheocharisSE,IliopoulosDG,Demopoulos

CA,ZabetakisI.2010.In vivoanti-atherogenicpropertiesofculturedgiltheadseabream(Sparus aurata)polarlipidextractsinhypercholesterolaemicrabbits.FoodChem120:831-6.

NasopoulouC,StamatakisG,DemopoulosCA,ZabetakisI.2011a.Effectsofolivepomaceandolivepomaceoilongrowthperformance,fattyacidcompositionandcardioprotectivepropertiesofgiltheadseabream(Sparus aurata)andseabass(Dicentrarchus labrax).FoodChem129:1108-13.

NasopoulouC,TsouprasAB,KarantonisHC,DemopoulosCA,ZabetakisI.2011b.Fishpolarlipidsretardatherosclerosisinrabbitsbydown-regulatingPAFbiosynthesisandup-regulatingPAFcatabolism.LipidsHealthDis10:213.

NasopoulouC,ZabetakisI.2012.Benefitsoffishoilreplacementbyplantoriginatedoilsincompoundedfishfeeds.Areview.LWTFoodSci.Technol.47:217-224.

RizosEC,NtzaniEE,BikaE.KostapanosMS,ElisafMS.2012.Associationbetweenomega-3fattyacidsupplementationandriskofmajorcardiovasculardiseaseevents.Asystematicreviewandmeta-analysis.JAMA308:1024-33.

SaravananP,DavidsonNC,SchmidtEB,CalderPC.2010.Cardiovasculareffectsofmarineomega-3fattyacids.Lancet376(9740):540-50.

ZabetakisI,AntonopoulouS,DemopoulosCA.2013.ThePreventionofAtherosclerosisbyFoodComponents:PolarLipidsversusOmega-3PUFAs.Commentaryonwww.athero.orgpublishedon22.1.2013(http://www.athero.org/commentaries/comm1119.asp).

More InforMatIon:Email: izabet@chem.uoa.gr

Negative environmental impact of olive pomace

24 | InternAtIonAl AquAFeed | March-April 2013

FEATURE

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Towards aquafeeds with increased food security

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