expert topic - tilapia

July | August 2012

EXPERT TOPIC - Tilapia

The International magazine for the aquaculture feed industry

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 form or by any means without prior permission of the copyright owner. Printed by Perendale Publishers Ltd. ISSN: 1464-0058

http://www.aquafeed.co.uk

14 | InternAtIonAl AquAFeed | July-August 2012

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July-August 2012 | InternAtIonAl AquAFeed | 15

TILAPIAEXPERT TOPIC

Welcome to Expert Topic, a new feature for International Aquafeed. Each issue will take an in-depth look at a particular species and how it's feed is managed.

1

Effects of dietary potassium diformate on juvenile tilapia – a performance analysis

by Christian Lückstädt, Animal Nutritionist, ADDCON, Germany

Global production of farmedtilapia in at least 85 countriesexceeded 3 million t in 2009and requires high-quality fish

feeds.Insuchintensiveaquacultureproduc-tion, bacterial diseases have been identifiedas amajor causeof economic loss topro-ducers. Feeding antibiotic-medicated feedsis a common practice to treat bacterialinfections. Prophylactic useof antibiotics asgrowth promoters in aquaculture produc-tionhasalsooccurredwidely.

However, growing awareness from con-sumersandproducersofaquaculturespecieshasresultedinademandforresponsibleandsustainableaquaculture.Regulatoryauthoritiesin most exporting countries now focus onthe misuse of antibiotic growth promoters(AGP) in aquaculture, while public attentionhas shifted towards sustainable productionmethods.

Thus, alternative additives to replaceAGPs,whichhavebeenbannedinEUanimalfeeds since 2006, have had to be tested.Dietaryorganicacids,andespeciallypotassiumdiformate – the most widely tested organicacid salt in aquaculture, are among the vari-

ous alternatives spearheading environmentalfriendly and nutritive-sustainable aquacultureapproaches.

Dietary potassium diformate (KDF) hasbeentested in tilapiaaquaculturesince2005and since then numerous publications andconference contributionson theuseofKDFin juvenile tilapia have been published fromEurope,AmericaandAsia.Thisstudyanalysedthe average impact of the additive from allpublishedstudiesonitseffectonperformanceparameterssuchasweightgain,feedefficiencyandmortality.

The final data-set contained the resultsof eight published studies, comprising 18trials with KDF-inclusion, which ranged from0.2% to0.75%andcovered3,040 fish.Datawere subjected to statistical analysis and asignificancelevelof0.05wasusedinalltests.Results are expressed as percentage differ-encefromthenegativelycontrolledfish.

The average level of dietary potassiumdiformate from the data-set in all treatedfish was 0.41percent. Only a numericalincrease of feed intake (2.1%) could bemonitored (P=0.16) compared to fishwithout the additive. However, the per-formance of tilapia, based on final weightwas significantly increased by 5.6 per-cent (P=0.009). Furthermore, the feed

conversion ratio of fish fed KDF wasalso significantly improved (P=0.012): thistime the improvement was 4.5 percent.Dataonmortalitywereinconclusive,sincesomeof the trialswerecarriedoutunderclean laboratory conditions, while othersemployedachallengewithpotentiallypath-ogenic bacteria, such asVibrio anguillarum,Streptococcus agalactiae,Streptococcus iniaeand Aeromonas hydrophila. In these cases,dietary KDF, ranging from 0.2 percent till0.5 percent reduced mortality (P<0.05)when employed against V. anguillarum; ittended to reduce (dosages between 0.2-0.6%)mortalitycausedbyS. agalactiae andA. hydrophila, while it had no effect (KDFranging from 0.25-0.75%) on mortalitycausedbyS. iniae.

In general, results show significantlyimproved growth and FCR in tilapia fedwith dietary potassium diformate, whileits beneficial impact against pathogenicbacteria seem to be bacterial-challengedependent.Ifcalculatedasfishproductivityindex, which is a function of weight gain,survival and FCR (Lückstädt & Kühlmann,2011), the improvement extended toalmost 17 percent (P=0.020). The use ofKDF in tilapia feeding is therefore sup-ported as a promising alternative in thecontemporaryaqua-feed industry inordertocontributetoanecologicallysustainabletilapiaproduction.

This paper was presented at the XV International Symposium on Fish Nutrition and Feeding Molde, Norway June 4-7, 2012. Originally published on www.engormix.com

More InforMatIon:Website: http://www.addcon.com

table 1: effects of potassium diformate in tilapia diets against negative control performance (responses as per cent of negative control) – data-set consists of eight published studies covering 3,040 fish

Dosage (%) Feed intake Weight gain FCr

0.41 +2.05 +5.59 -4.46P.level 0.162 0.009 0.012

14 | InternAtIonAl AquAFeed | July-August 2012 July-August 2012 | InternAtIonAl AquAFeed | 15

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Tilapia cage farm management in Brazilby Alberto J. P. Nunes, from the Instituto de Ciências do Mar – Labomar, tilpia cage farm management specialist. Originally published in Global Aquaculture Advocate

Much of Brazil’s expandingtilapiaaquaculturetakesplacein floating cages with sturdyframes and nets made from

plastic-coatedsteelorpolypropylene.

Althoughlargercagesarealsoused,mostcages have small volumes up to 20m3 thatsupport high stocking densities and intermit-tent harvesting without overstressing thefish. Earthenpondsmaybeused for thenursery of fry, but compartments incagesaremorecommon.Sizegradingisamajormanagementcomponent.

Tilapia were first brought toBrazil in1953,butonlyover thepast decade has tilapia farminggrowntocommercialscale.Since1999,theindustryhasexpandedat an average annual growth rateof 18 percent. In 2009, the BrazilianMinistryofFisheriesandAquaculturereportedthetilapiaharvestwas133,000metrictonnes.Over the years, Brazilian farmers have useda number of tilapia strains, starting with theFloridaredandmorerecentlythegeneticallymale tilapia.Nile tilapia,Oreochromis niloticus,Chitralada strain, brought from Thailand in1995,hasestablisheditselfasthemainstrainfarmed in the country. Much of the tilapiaaquaculturetakesplaceinfloatingcagesnearmanyofBrazil’scoastalareas.

Cage characteristicsBrazilholdsabout10millionhaoffreshwa-

ter indams, rivers, lakesandman-made res-ervoirs.Floatingcageshavebecomethemostpopular system for rearing tilapia in Brazil inareaswithsuitablewaterquality,flushingratesandwaterdepth.

Tilapiacagesaresimpletobuild,inexpen-sive(US$400 fora6-m3cage)andeasy tomanage. Cages are usually constructed withrigidorflexiblenetsmadefromplastic-coatedgalvanized steel, stainless steel or syntheticfiberssuchaspolypropylene.

Steel nets are more widespread, as theybetter resist predatory fish such as the pira-nhas found in some inland areas in thecountry. Cage frames are made from stain-less steel or galvanized steel. Strong, long-life,high-densitypolyethylene framesare lesswidely available and more costly, but havebecomethechoiceoffarmsthatoperatewithmedium-volumecages.

In sites close to shore, stationary cagesare spaced two to four metres apart ingroupsanddockedwithanchoringpolesfixedinshore. Otherwise, submerged chains andropes attached to concrete bottom weightsare used as mooring systems. To facilitatedaily management, many farms now adoptwalkways made from wood attached toemptybarrelsorplasticcontainers.

Most cages used for tilapia rearing havesmallvolumesoffourto20m3.Thesecan be round or square inshapewithheightsnotgreaterthantwometres.Thecagescan

safely operate with high stocking densities(starting at 120 kg tilapia/m3) due to rapidwaterexchange.

Since much of Brazil’s tilapia sales aredomesticandretail,small-volumecagesallowthe harvest of fewer quantities of fish with-out imposing stress on the greater stockedpopulation.Ascagesmovebeyond10m3involume with monthly harvests exceeding 10metrictonnes,farmsrequireamoderatelevel

ofcapitalinvestmentandcashflow,andscaleharvests for consistent sales and productionflow.

Tilapia farms that operate with cagesbeyond 300 m3 in volume are sometimesvertically integrated from fingerling produc-tion to fish distribution. They operate withprocessing plants and sales contracts thatrequiretheharvestoflargevolumesoftilapiaata time. In larger-volumecages, final stock-ingdensitiesarereducedto60kgoffish/m3.Theyhavethedisadvantageofpoorflexibilityandmaneuverability, buton theother hand,canrepresentsignificantsavingsinlaborforce.

NurserySex-reversed tilapia are usually sold to

growoutfarmsasfrywithwetbodyweightsbetween0.2and0.5g.Athousandtilapiafrycost US $30 to $45, depending on quality,location and availability. When available atshortdistances,somefarmerspreferacquiringjuvenile fish of 10- to 30g weight, althoughtheir prices may exceed $80/1,000 fish. Atthis stage, fish mortality can be significantlyreducedandthegrowoutcycleshortened.

Earthenpondsmaybeusedforthenurs-ery of Chitralada fry prior to stocking incages. However, cages equipped internallywithflexible5mmmeshnetsareusuallymore common, as

they facilitate fish han-dling and transfer to grow

out cages. In cages, it takes fivetoeightweeks togrow0.5g fry to30g

juveniles,dependingonstockingdensity,feedandwaterquality.

Size GradingTilapia growth can vary widely within the

samestock,especiallywhenthefisharesubject-edtohighdensity.Thisisinpartduetogeneticdifferences, but also because of competitiveinteractionsamongfish.Somefishoutcompeteothersforfeedandconsequentlygrowfaster.As

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aresult,sizegradingbecomesamajormanage-mentcomponentoftilapiacagefarming.

When tilapia are transferred to differentcages,italsoallowsmovingthestocktocleanunits with larger mesh sizes, which promotesgreaterwaterexchangewithintherearingunit.From 5mm mesh sizes, 10g fish are usuallymoved tocageswithmeshsizesofup to15mm.Then 30 to 200g tilapia are heldwithinnetsof15to25mmmesh.Themeshonnetsforfishlargerthan200gis25mmorwider.

Grading frequencydependsonanumberof variables, including the targeted fish sizeatharvest,numberofcagesavailableonsite,stocksizevariation,degreeofprevalentstressand health status of the stocked population.Many farmers target tilapia above 900g inweight to achieve premium prices. For thisfishweight,gradingcanbecarriedouttwotothreetimesinaproductioncycle(Figure1).

Duringtherainyseason,whenfishbecomemore susceptible to disease outbreaks, thereisareductionintilapiastockingdensityaswellas grading frequency. When size grading isadopted,finaltilapiabodyweightvariationcanbereducedfrom40percentatinitialstagestoabout 15 percent at harvest time. Tilapia areoftensortedintofoursizecategories,withthesmallest,mostchallengedfishremovedasearlyaspossiblesincetheirdelay ingrowthcannotberecoveredduringtheproductioncycle.Fish

areusuallysortedmanuallybyeye,butinlargeoperations,thisprocedurecanbemechanised.

Feeds, feedingCage-farmed tilapia in Brazil received

only extruded diets. Feed protein content,pelletsizeandsuggestedfeedingratesmayvary according to the feed manufacturer.Fish feeds tend to be high in protein con-tent at initial stages anddropas fish attainlargersizes(Table1).Growoutandfinishingfeedsareusually32percentinproteincon-tentandmayrepresentupto80percentofall feedingcostsatacage farm.Feedcoststoproduceaonekilo tilapiacanrangeUS$1.10-1.30/kg of fish harvested. As such,feedmanagementiscriticaltotheeconom-icsofacageoperation.

Todeterminemaximumrationsizes,farm-ersusually followsuggestedrates fromcom-mercial feeding tables. However, rations areadjusted on a daily basis depending on fishappetite. In small-volume cages, rations arenever delivered in full amounts. Initially, fishcanbe fedonlyhalfof thecalculated ration.The remainder isoffered if the first ration isfully consumed within 30 minutes after dis-tribution.Afterthisperiod,uneatenfeedcanbeoversaturatedwithwater,andtheheavierpelletsexittheconfinedfeedarea,leadingtofeedloss.

Cageoperationsequippedwithwalkwaysallowmoredetailed inspectionsof feedcon-sumption. They facilitate feed handling andstorage,andpromotefeeddeliverytoasoftenas eight times a day during grow out com-pared to three times when distributed fromfeedboats.Walkwaysalsoallowthecollectionof fishdebrisandmorefrequentcleanupoffeedingringsornetcurtains.

PerspectivesTilapiacagefarmingwillcontinuetogrow

quickly in the years to come in Brazil toreduce the increasing domestic deficit offisheries products in the country. Tilapiaare mostly marketed fresh and degutted atweights of 700 to 900g. Farm gate pricesrangeUS$2.00-2.80/kg.

TodayagreatproportionofBrazil’stilapiaproduction is consumed in the countryside,butthefisharealsonowfoundinlargesuper-market chains, restaurants and fish marketsall over the country. As capture fisheriescontinue to decline in Brazil and more cityresidentslearntoappreciatetilapia,increasingdemandwillfurtherdrivenewentrepreneursinto tilapia aquaculture. In this new scenario,medium-size cages and more mechanisedpracticeswillemergetokeeppacewithlarge-scale production and more-efficient opera-tions.


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Tilapia genetic strains and hatchery technologyby Eric Roderick

Tilapia isadiversegroupofover100species,butsurprisinglyonlyahandfulofspeciesareculturedcommerciallyandonlyonespecies,theNiletilapia,

Oreochromis niloticusaccountsfor95percentofglobalproduction.

Culture systems range from small backyardoperationsproducingafewfishtosustainasmallfamily, to huge agro-industrial units producing

over 20,000 metric tonnes annually. With therapidgrowthof theglobal tilapia industryoverthe past 25 years, genetic improvement pro-grammesenable amoreprofitable industry tobenefit from the increasedpopularityof tilapiaasaglobalfoodcommodity.

From humble beginnings being farmed forthePharaohsinAncientEgypt4,000yearsago,the Aquatic chicken is now a very importantglobally traded commodity with productionworldwideof3.23millionmetrictonnesin2011andstillgrowing.

SupermalesMost commercial farms only grow male

tilapia,whichgrowmuchlargerandfasterthanfemales. This was initially achieved throughmanual hand-sexing of the fingerlings, and dis-cardingthefemales,whichwaslabourintensive,

inconsistent, and wasteful. It was then foundthat certain hybrids between different tilapiaspecies(O.niloticusandO.aureus)gaveveryhighpercentmaleprogeny.Thedownsidewiththistechnique was that it required hatcheries toholdtwoseparatestocksoftilapiaspecies,andas thepurityof tilapia stocksdeteriorated, thetechniquebecameunviable.

Researchers thendiscoveredthat tilapia fry,whenfedmalesexhormonesforthefirstmonthafter hatching, were able to change sex, from50-50maletofemaleratio,toratiosofalmost100 percent male fry. This is a highly variabletechniqueduetohormonepurityandoperatorexperience.

One of the major challenges facing theindustryisthatuseofMethylTestosteronewillbephasedout.This isovercomeby the latesttechnology to effectively provide allmale fry -theYYMaleTechnologydevelopedbyFishgen.AftermanyyearsofresearchintheUKandinthe Philippines, Fishgen produced supermaletilapiawhichhad twoYchromosomes insteadof the usual Y and X chromosome. Femaleshave two X chromosomes. These supermalesproduceonlymalefryaddressingtheproblemsofafuturebanonhormonalsexreversal.

Which strainDeciding on which commercial strain of

tilapia to use in a new tilapia project can bedaunting,andtherearemanycommercialstocksavailableglobally.The farm’s locationcanhavea deciding influence as there are restrictionson importation of some strains from somecountries, to minimise disease and biodiver-sityissuesparticularlyinAfricawheretherearemanyuniqueendemicstrainsoftilapia,requiringprotection fromcontaminationbythecarelessintroductionofnewgeneticlines,whereescap-ees could interbreedoroutcompetewith thepureendemicspecies.

The big fourThere are currently four main genetically

improved commercial lines that are globallydistributedandproventobefastgrowing.Thebiggest genetic improvement programme wastheGIFTproject(GeneticallyImprovedFarmedTilapia) and the current stock was originallyproducedfromeightstrainsof theNileTilapiacollectedfromAfricainthe1980s.

After extensive selective breeding pro-grammescarriedoutinthePhilippinesbetween1988 and 1997by ICLARM (NowWorldFishCenter)incollaborationwithAKVAFORSK(TheInstituteofAquacultureResearchinNorway)anew strain was produced and distributed glo-bally.WorldFishCenterhasmovedtoPenang,Malaysia now and the breeding programme isstillcarriedonscientificallyandcommercially inbothMalaysiaandthePhilippines.

The commercial rights to a recent GIFTgeneticlinewassoldtoGenomar(aNorweigianVenture Capital Genetic Improvement com-

pany) a few years ago and is now marketedgloballyasGenomarSupremetilapia(GST)andtheprocessedfishasTRAPIA(traceabletilapia)ensuringfullgenetictraceabilityoftheirproductsto the food industry. Trapia is produced inGenomar’s cage farms in lakes inMalaysiaandmainlyexportedtotheUSA.

SincethesaleoftheGIFTlatestgeneticlinesto Genomar, the Philippines have carried onwith their own Genetic Improvements of theGIFTlineandmarkettheGIFTExcellinenow.TheselinesareallbasedontheoriginalgeneticstockscollectedinAfricainthe1980s.

Anotherwell-known stock is theChitriladastrainwhichisfarmedextensivelyinThailand.ItoriginatedasagifttotheKingofThailandbytheEmperorofJapanin1965,andwasmaintainedas a pure line in the Royal Jitralada Palace inBangkokformanyyearsbeforebeingdistributedthroughout Thailand by the Thai Departmentof Fisheries in 1967. Since then it has beenimproved by selective breeding programmesandisnowwidelyfarmedinSouthandCentralAmerica, particularly Mexico and Brazil. ThisstockalsooriginatedfromEgypt.

The only other tilapia genetic line com-mercially usedextensively around theworld istheYYSupermalestrain,developedbyFishgenintheUK.ThisstockisalsobasedontheNileTilapia from Egypt, but the main differencebetweenthislineandalltheothersavailable,isthatnohormonesarerequiredtosexreversethe fry for growout, as theYY supermale hasbeenspecificallybredtosireonlymaleoffspring.

Hatchery systemsTilapia hatchery systems are diverse with

costofconstructionandproductionoftilapiafryvaryingenormously, frombasicpondhatcheriesin tropical countries costing almost nothing, toexpensivehigh-techbio-secure indoor recircula-tion systems. The low-cost breeding systemsutilise simple earth broodstock ponds, with ashallowareaaroundtheedgewherethefryoncereleasedfromthefemale’smouth,tendtocon-gregateintightshoalsandarecollectedwithlargedipnetsorsmallseinenets,onadailybasis.Largerhatcheriesuselinedpondsinpoly-tunnelswhichgivebettertemperaturecontrol,biosecurityandpredatorprotection.Thefryareincubatedbythefemalewhich is lessefficient than removing thefertilisedeggsfromthefemale’smouthandusingartificialincubatorstohatchthefry.

Manyoftheworld’slargesttilapiahatcheriesare inAsia,where75percentof global tilapiaproductiontakesplace.TheyutiliseHapa-basedproductionsystems,wherethebroodstockarebredinlonghapas(netpens)andtheeggsareharvested from the female’s mouth every fivedays.Thisisdonebyopeningthebuccalcavityofthefemaleandgentlyrinsingtheeggsoutofthemouthintoabucket.

Global perspectiveWithglobaltilapiaproductionstillgrow-

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ing steadily, hatcheries are alsoexpanding to provide fry for thegrow-out farms and some of thebiggest hatcheries now have thecapability to produce one millionfryperday.

At present themain tilapia pro-ducing countries are China, Egypt,Thailand, Indonesia, Philippines,Costa Rica, Ecuador, Mexico andHonduras.Thereare largehatcher-ies in all these countries but thebiggestfarmsareverticallyintegratedunits which produce their own fryto minimise biosecurity issues andensuresupplyoffry.

RegalSpringsisoneoftheworld’slargest tilapia businesses, producingover70,000metrictonnesin2010inseveral countries around the world.ACIinCostaRicaisoneofthelarg-estindividualfarms.Bothcompaniesexport all their production as freshfillets to the USA. Biomar is justcompleting itsbrandnewhigh techfeedmillveryclosetotheACIfarmto meet the growing demand fortilapiafeedinCentralAmerica.

Future marketsWith the tilapia market firmly

establishedandgrowingintheUSAand globally, future challenges for

tilapiaproducerswillbetofindnewmarketsand to overcome stiff competition fromPangasius species (Basa and Tra) import-ed from Vietnam. This is especially true inEuropeanmarketswhichisstillseenasanewhighvaluemarketfortilapiaproducersaroundthe world. Spain imports 20 percent of theEUtotalandPoland33percentbutthesearemainlyfrozentilapiafromChinawithdemandfuelledbythelowpricesreflectingthecurrenteconomicdownturnthroughouttheEU.

Rapidly expanding importers of tilapiaare Russia and the Middle East, but asChina becomes far wealthier, consumingmoreof itsown tilapiadomestically,priceincreases and possible shortages of tilapiaas an export commodity are possible.Manycountriesarerampingupproductionto fill this perceived new demand. TheseareVietnam,Bangladesh,Brazil, EgyptandMalaysia, where government support ishelping to drive this new wave of expan-sions.Themaingrowthareasare in valueaddedproductsparticularlyintheproduc-ingcountriessoincreasingprofitability,andfilling new and growing markets. Tilapia’sfutureisrosy.

More InforMatIon:Eric Roderick, FishGen Tel: +44 7973 135609Email: [email protected] Website: www.fishgen.com


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Feed formulation and feeding strategies for tilapiaby Ingrid Lupatsch, Centre for Sustainable Aquaculture, Swansea University, UK

Tilapia are now the world’s secondmostpopulargroupoffarmedfishafter carp. Worldwideproductionexceeded2.5million tons in2007

accordingtoFAOanddemandcontinuesatasteadypace.

Tilapia are farmed worldwide in inlandaquaculture in various kinds of facilities andproduction strategies. The majority is stillgrown extensively in polyculture but moreandmoreintensivemonoculturesystemsarebeing used where the manufactured feed istheonlysourceofenergyandprotein.

Tilapiaareoftencalled the ‘aquaticchick-en’.Theirsuccessisattributedtoatoleranceto wide ranges of temperature and salinity,resistancetodisease,theirabilitytoreproducein captivity, and their capacity to grow wellat high stocking densities, which make themfeasible for farming under various culturesystems.

Tilapia as herbivores areperceived tobemoresustainableandwhilstfeedingonalowtrophic level, are able to convert low costfeedintohighqualityprotein.Thereiscontin-uedcriticismthatcarnivorousfisharethoughttorequirehighlevelsofproteinintheirfeeds(that are mostly supplied by fishmeal) while

most herbivores such as tilapia are fedfeeds containingonly25 to30percent

protein.Thisgivesthe impressionthatherbivoresaremoreefficientconvert-ersofproteinintogrowth.

However, expressing proteinrequirement based solely on dietaryinclusion levels is incomplete if feedintakeisnotconsidered.Proteinintake

istheproductoftheproteincontentofthe feed and the total amount of feed

consumed. As such the protein demandperkiloof fishproducedwill giveaclearer

pictureoftheoverallefficiencyofthespeciesinquestion.

Generally speaking, in order to formulatefeeds for fish two main issues have to beaddressed:a)whataretherequirementsandb) how can we cost-effectively meet thoserequirements.

First,tilapia-likeallanimals-needenergyand protein. This seems trivial, but the chal-lenge istodeterminehowmuchenergyandproteinhastobesuppliedtoguaranteeopti-malgrowthandmostefficientfeedutilisation.

Second, what are the sources of energyand protein? Various potential feed ingredi-entshavetobeevaluatedfortheirnutritionalvalue, chemical composition and their avail-abilitytothefish.

Calculating requirements Nutrient requirements are generally

defined for animalsof a given age and for aspecificphysiologicalfunction,suchasmainte-nance,growthorreproduction.Infishfarminggrowth is one of the major goals. Growthmeansdepositionofnewbodycomponents,whichinfishconsistmainlyofproteinandlipidbesideswater.

The feed has to supply the material forbuildingnewtissue,butalsotheenergyneed-edtodepositthenewgrowth.Inadditiontothese, energy and protein for maintenancehave to be supplied as well. Therefore, thisbasiccalculationdictatesthattheenergyandprotein requirement of a growing fish is thesumofitsneedsformaintenanceplusgrowth.

The energy and protein requirement formaintenance at a constant temperature isprimarily dependent on body size. It is pro-portionaltothemetabolicbodyweightintheformoftheequation,axBW(kg)b,whereaisaconstant,characteristicofacertainfishspe-ciesatasettemperatureandb istheexpo-nent of the metabolic weight which in fishhasbeendetermined asb=0.80 (Lupatschetal.2003).

Therequirementforgrowthisdependenton the amount and the composition of theweight gain including the metabolic costs todepositnewgrowth.

Daily energy requirements per fish inunits of digestible energy can therefore beexpressedas:

Digestible energy needs (kJ) = a × body weight (kg)0.80 + c × energy gain (kJ)

Where c = cost of production in units of dietary energy to deposit energy as growth.

Thesameapproachisusedforthequan-tification of protein, except for the use ofa different exponent of b = 0.70 for bodyweightasdetermined forseveral fishspecies(Lupatsch et al. 2003, Lupatsch and Kissil,2005).

Digestible protein needs (g) = a × body weight (kg)0.70 + c × protein gain (g)

Where c = cost of production in units of dietary protein to deposit protein as growth.

Using this approach energy and pro-tein requirements are quantified as abso-lute requirements per fish body mass andanticipated daily weight gain and only thenexpressedasaninclusionlevelinthefeed.

The necessary parameters to obtain arethusthefollowing:

Growth data and feed intake Aprerequisiteforestimatingfeedrequire-

ments of tilapia is to define its maximalpotential forgrowth.Thismodelling requiresgrowthdatafromtrials,wherefeedsupplyintermsof energy and nutrients is not limitingandoptimalgrowingconditionsaremet.Itisthoughnecessarytodefinetheseparametersfor different stocks or strains as differentselection programs result in faster growingstrainsofallmaleOreochromis niloticussuchasforexampletheGIFTstrain.

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Figure 1: Energy requirements of tilapia for maintenance and growth (at 27°C)

Figure 2: Protein requirements of tilapia for maintenance and growth (at 27°C)

The following equations are all based ontrialscarriedoutinIsraelusingmalehybridofO. niloticusxO. aureusatawatertemperatureof27°C.

The equation defining the relationshipbetween daily weight gain and fish sizeappearsbelow:

Weight gain (g / fish / day) = 0.12 × Body weight (g) 0.547

Another prerequisite is an assessmentof the maximum voluntary feed intake, theamountorbulkthatthefishisphysicallyabletoconsume,thisisneededtoadjusttheener-gydensityandnutrientdensityofapotentialfeed. The following relationship betweenvoluntaryfeedintakeandfishsizewasfound:

Feed intake (g / fish / day) = 0.15 × Body weight (g) 0.600

Composition of weight gain As a large proportion of the energy and

protein consumed by the fish is retained asgrowth,thecompositionofthegainisamainfactordeterminingthesubsequentenergyandproteinrequirement.Whenmeasuringwholebody composition of fish at increasing sizes,

each gram weightgain is assumed toequalthebodycom-position at a certainsize.

There is anincrease in energycontent with fishsize, whereas theprotein contentremains quite con-stant at 160 mg/gfish

Energy (kJ / g fish ) = 5.53 × BW (g)

0.055 Protein (mg / g fish

= 160.2)

Thefact thatpro-tein content remainsquitestableandener-gy content is increas-ingwithincreasingfishsizeistypicalformostfish (Lupatsch 2009).However, comparedto species such assalmonorgiltheadsea

table 1: Protein and energy requirements of tilapia grown at 27°C

Body weight, per fish 25g 150g 300g

Weight gain1, g / day 0.70 1.86 2.72

energy requirement

Demaint2, kJ /fish /day 2.90 12.17 21.18

Degrowth3, kJ/fish /

day 7.42 21.81 33.11

Dem+g4, kJ /fish /day 10.32 33.98 54.29

Protein requirement

DPmaint5, g /fish /day 0.048 0.170 0.276

DPgrowth6, g/fish /day 0.238 0.634 0.926

DPm+g7, g /fish /day 0.286 0.803 1.202

DP/De ratio g/MJ8 27.7 23.6 22.1

1Predicted weight gain for tilapia at 27°C

2DE required for maintenance: 55.5 x BW (kg) 0.80

3DE required for growth: (weight gain x body energy) x 1.61 (cost of production)

4DE required for maintenance and growth

5DP required for maintenance: 0.64g x BW (kg) 0.70

6DP required for growth: (weight gain x body protein) x 2.13 (cost of production)

7DP required for maintenance and growth

8Dietary DP/DE ratio for optimal protein utilisation


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bream, tilapia can be catego-risedasaleanfish,afactwhichintheendwillaffectthedietaryproteintoenergyratio.

Maintenance requirements and efficiency

To determine the main-tenance requirement as wellas the relationship betweenweight gain and feed intake,groups of tilapia are fedincreasinglevelsoffeedswitha

knowndigestibleenergy(DE)anddigestiblepro-tein(DP)content.Feedinglevelsincludedazerogroup(nofeed)uptomaximumvoluntaryintakeatapointwhenthefishrefusedtoeatmore.

Figure1demonstratesthattherelationshipbetweendailyDEconsumed (x) andenergyretained(y)islinearandcanbedescribedbythefollowingequation:

y = - 34.4 + 0.62 x

TheDE(kJ)requirementformaintenance(noenergygainorloss)canbefoundwherethey-axisis zero. According to the equation above, themaintenancerequirementperdaywouldamountto34.4/0.62=DEmaint=55.5kJ×(kg)0.80.

TheslopeofthelineinFig.1isameasurefor the efficiency of energy utilization forgrowth. For tilapia this amounts to 0.62, orin other words, 62 percent efficiency. Thereciprocal value 1/0.62 = 1.61 is a measureforthe‘costofproduction’inunitsofDE(kJ)todepositoneunitofenergy(kJ)asgrowth.

Requirementforproteincanbeobtainedinasimilarmanner(Fig2).Therelationshipbetweenprotein intake (x) andprotein gain (y) referringtoametabolicbodyweightofkg0.70isasfollows:

y = - 0.30 + 0.47x

MaintenancerequirementDPmaint(g)=0.64×BW(kg)0.70andadditionally2.13unitsofDP

(g) are needed todeposit one unitof protein (g) asgrowth.

Practical application

Hence, withthe parametersobtained energyand proteinrequirementsfor tilapia can becalculated andadaptedtochang-ing conditions forthe duration ofa growth period(Table1).

Ingredient evaluation and feed formulation

Asmentionedbefore,oncetherequirementsareknown,variouspotentialfeedingredientshavetobeevaluatedfortheirnutritionalvalue,chemicalcompositionandtheiravailabilitytothefish.Table2providesnutrient composition includingdigest-ibilitydataofseveralingredientsthatarecommonlyusedinaqua-feeds(Sklanetal.2004).

Table 3 describes two potential feedsthatcouldbeformulatedfromcommerciallyavailable ingredients. The feeds describe a30 percent protein feed, commonly usedin tilapia farming and a40percentproteinfeed.

The full amount of protein consumed bytilapia is a function of the quantity of feed andthe protein content of that feed. As the dailyrequirementsforproteindonotchange,thefeedamount fedhastobehigherwhenofferingthelowproteinfeed(Table4),whichwillresultinanincreasedFCR.Inthiscaseonehastoconsiderthecostofgrowingonekgoffishandnotjustthecostper1kgoffeed.

The results presented here indicate, thatherbivores such as tilapia do not utilise pro-tein more efficiently than other fish species(Lupatsch, 2009), but their advantage mightbe,thattheycouldbefedlowerproteindietsas they are able to consumehigher amountsof feedcomparedtocarnivores.This facthasbeen highlightedby Lupatsch andKissil, 2005whilstcomparingwhitegroupertogiltheadsea-bream.However,itisimportanttorecognizethateventilapiamightreachtheirphysicallimitstoconsumeallthefeedtoacquiretheproteinneededformaximumgrowthespeciallyatthejuvenilestages(Table4).

Using this approach toquantifyingenergyand protein demands in tilapia, it is possibletoestimatethebiologicalandeconomicaleffi-ciencyofdifferentfeedsandculturesystems.

References

Lupatsch,I.,Kissil,G.Wm.andSklan,D.(2003).Definingenergyandproteinrequirementsofgiltheadseabream(Sparusaurata)tooptimizefeedsandfeedingregimes.TheIsraeliJournalofAquaculture-Bamidgeh,55(4),243-257.

Sklan,D.,Prag,T.andLupatsch,I.(2004).ApparentdigestibilitycoefficientsoffeedingredientsandtheirpredictionindietsfortilapiaOreochromis niloticus×Oreochromis aureus(Teleostei,Cichlidae).AquacultureResearch,35,358-364

Lupatsch,I.andKissil,G.Wm.(2005).Feedformulationsbasedonenergyandproteindemandsinwhitegrouper(Epinephelusaeneus).Aquaculture,248,83-95.

Lupatsch,I.(2009)Quantifyingnutritionalrequirementsinaquaculture–thefactorialapproach.In:Newtechnologiesinaquaculture:improvingproductionefficiency,qualityandenvironmentalmanagement.BurnellG.andAllanG.(Eds).WoodheadPublishing,Cambridge,p417-439.

table 3: Proposed feed formulations for two sets of commercial feeds – low protein and high protein (for ease of presentation vitamins, minerals and other supplements are considered under ‘others’).

Feedlow

proteinHigh

protein

Ingredients (g kg-1)

Fish meal 100 200

Corn-gluten 100 160

Soybean meal 120 160

rapeseed meal 120 130

Sunflower meal 120 130

Wheat meal 180 70

Corn meal 140 70

Plant oil - 50

others 120 30

estimated composition ( per kg as fed)

Dry matter (DM), g 920 920

Crude protein, g 298 405

Gross energy, MJ 16.9 19.7

Crude lipid, g 29 87

ash, g 72 77

Carbohydrates, g 521 351

Digestible energy (De), MJ 11.9 15.3

Digestible protein (DP), g 263 363

DP / De ratio, g / MJ 22.1 23.7

table 4: Proposed feeding table for tilapia and expected FCr whilst feeding a high or low protein feed.

Body weight, per fish 25g 150g 300g

Weight gain1, g / day/ fish 0.70 1.86 2.72

Voluntary feed intake, g/day/fish 1.0 3.0 4.6

De requirements, kJ / day/ fish 10.3 34.0 54.3

DP requirements, g / day/ fish 0.29 0.80 1.20

Feed selection (protein) low High low High low High

required feed intake , g/day/fish 1.1 0.8 3.0 2.2 4.5 3.3

required feed intake, % biomass / day 4.4 3.2 2.0 1.5 1.5 1.1

FCr 1.56 1.13 1.64 1.19 1.68 1.22

table 2: nutrient composition of selected ingredients used in practical feed formulations (per kg as fed)

Crudeprotein, g

Digestible protein, g

Grossenergy, MJ

Digestible energy, MJ

Fish meal 635 573 19.91 17.76

Corn gluten meal 604 559 21.65 18.06

Soybean meal 441 398 17.68 14.94

rapeseed meal 366 311 19.49 11.17

Sunflower meal 378 336 17.87 11.70

Wheat meal 118 94 17.69 12.72

Corn 79 59 17.52 10.76


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Sustaining the supply of Chinese tilapia

by Han Han, Program Manager, Sustainable Fisheries Partnership

Tilapia, the third most internation-ally traded aquaculture product aftersalmon and shrimp, has been widelyfarmedinChinasincethe1950s.With

strong governmental support for the researchanddevelopmentofhybridsandculturetechnol-ogy,Chinesetilapiaaquaculturehasgrownrapidlyfromtheinitialstagesinthe1960s,toexpansionintheearly1980s,andthentolarge-scalefarmingandprocessing inthe2000s.Recentyearshavewitnessed a stable annual production of 1.1or1.2millionmt,abouthalfoftheworldtotal.Guangdong,Hainan,GuangxiandFujianprovincesinSouthChinahavebecometheworldhuboffarmed tilapia thathasbeenmainly supplied toNorthAmericanandEuropeanmarketsforthepastdecade.

Tilapiawas rankedAmerican’s fourth favoriteseafood in 2011. The so-called ‘aquatic chicken’is popular in different forms, including live, fresh,frozenaswhole, frozen fillets,gutted,guttedandscaled, fillets, skin-less, andboneless. In2010,USimportsoftilapiafromChinatotaled139,863mtatavalueof$555million,andincreased22percentinvolumeand36percentinvalueoverthepreviousyear.AccordingtotheFAO,EUimportsoffrozentilapiafilletduringthefirstquarterof2011postedamarginalgrowthof3.2%fromthesameperiodin2010withChinasupplyingnearly90percentofthesharetomarket.Meanwhile,Chinahasseenitsexportof tilapiamakingnewpath intocountrieslikeCameroon,Ghana,CongoandUnitedArabEmirates.

Problematic growthSuchphenomenalgrowthinbothsupplyand

demandacrosstheworldinevitablyfacessustain-abilitychallenges.Overthepast20years,ageneraltrendtowards intensification intilapia farminghasled to an increasing dependence on formulatedfeeds and freshwater supply. Poor management

andunsustainableuseofwaterandfeedsinvariablylead to contamination in receiving water bodies,diseaseoutbreaks,cropfailure,andexcessiveuseofantibiotics.Reflectingtheissuessurroundingthegrowth of the tilapia industry worldwide, Chinastands on the frontline facing the challenge ofmaintainingasteadyyieldwhileminimisingenviron-mentalandsocialimpactsofaquaculture.

The risks of environmental degradation anddiseaseassociatedwiththerapidintensificationofaquaculture have resulted in unfavorable assess-mentsofChinesetilapia inanumberofseafoodguidespublishedbyNGOs.Chinesetilapiafarminghasbeenchallengedmainlyonthefollowingissues:

• Theimpactonpublichealthfromtheuseofartificialhormonesandantibiotics

• Farmeffluentsandwastesdischargedwith-outpropertreatment

• The impact on biodiversity from escapedtilapiagiventhattilapiaisnotanindigenousspeciestoChina

• Theuseoffishmealincompoundfeedsanditstraceability

• Potentialconflictswithotherlandandwaterusers

More complicated and problematic scenariosmight appear, as global warming will probablyexpand the geographic range for some farmedtilapiaandenhancethesurvivalofescapees,aswellasincreasingthefrequencyandseverityofextremeweatherevents(i.e.floodsanddroughts).Thecur-rent challenges in accessing sufficient amountsofcleanwaterwillbeaggravatedasChina’sindustrialdevelopmentcontinuesitsrapidgrowth.

The problems facing tilapia aquaculture inChinaareattributedtoa lackof scientificzoningand regional planning, poor farm-level manage-ment,farmers’insufficientknowledgeofsustainablepractices, and inefficient regulatory enforcement.TheChinesegovernmenthasestablishedregionaland national technology support teams with aseriesofstandardstoregulateantibioticsusageandeffluentdischarge,aswellas investing inresearchanddevelopmentregardingtilapiabreeding,feed-ing,andprocessinginrecentyears.However,theimprovementshavebeenlimited.

Exploring solutionsTo identify solutions, we first need to both

quantitatively and qualitatively identify the prob-lems. Unfortunately, when assessing Chinesetilapia’s environmental impact, very limited dataisavailabletothepublic.Neithershort-termfarm-leveldata,norlong-termregional-scaleinformationiseasily accessible and theenvironmental impactof tilapia farming has never been systematicallyassessedinChina.

Although farm-level certification guaranteescompliancewithspecificstandardsatanindividualfarm this does not provide information aboutenvironmentalimpactsandrisksataregionallevel.Giventhelargenumberoffarmsconcentratedinareas where both agricultural and industrial sec-torssharewaterresourcesitisclearthatregionalassessments are highly desirable. Such studies

would examine direct pollution and disease riskas well as the biodiversity impact of tilapia onindigenousspecies(aparticularconcern inwarmareaslikeHainanIsland,theonlytropicalprovincein China, where wild tilapia can easily survivethroughwinter).

Some of the existing Chinese tilapia farmingregulations and practices do not match inter-national standards, which is critical in meetingthegrowingdemand foreco-labelcertification inexportmarkets.Thiscouldbeimprovedthroughbuildingamulti-stakeholderdialoguewitheffectiveknowledge-sharingandinformation-exchange.

Buyersandretailersneedtobeinformedaboutprogressonsustainabilityissuesthroughbothwrit-ten information and face-to-face communicationwith producers and suppliers. Guided trips tofarmsandplantswillnotonlybringmoreattentionandacknowledgementtotheissues,butalsohelpbuyers understand the specific support needsofindividual aquaculture operations. Their face-to-facecommunicationwith thepolicy-makerswhoregulateChinesetilapiaaquacultureonthegroundwillalsoenhanceawarenessofsustainabilityissues,thusfacilitatingtheadoptionofimprovedpolicies.

Buyers can also encourage the sustainablesourcingof feedsbyaskingtheirsupplierstofindouttheingredientsoffeedandwhereitiscomingfrom(i.e.thetraceabilityandtransparencyofrawmaterialssuchasfishmeal).

Giventhelargenumberofbuyersandsuppliersit is also essential that stakeholders participate inpolicyroundtablesbothwithinandacrossregionstoeffectivelybuildconsensusaroundpoliciesandpracticesandtodevelopconsistency inprocure-mentstandards.

Where SFP’s Aquaculture Improvement Projects can help

Sustainable Fisheries Partnership (SFP) is anindependent NGO that promotes sustainablefisheriesandaquaculturebyengagingstakeholdersineffectivedialoguestomobilisethesupplychaintowards sustainability. The organisation providesstrategic and technical guidance to seafood sup-pliers and producers, helps convene them withother like-minded companies in fishery improve-mentprojects(FIPs)andaquacultureimprovementprojects(AIPs),andbuildsconsensusaroundspe-cificimprovementsinpolicies,marineconservationmeasures,andfishingandfish-farmingpractices.

SFP involvement in China started in 2007,whentheorganisationbegantoadvisekeycorpo-ratepartnersontheirtilapiaprocurementpoliciesand sourcing, evaluating sources in Hainan andGuangxiprovinces.From2008to2010,SFPcon-ductedauditson10tilapiafarmsinsixcountries,comparing the three main international stand-ards:GLOBALG.A.P,GlobalAgricultureAlliance’sBest Aquaculture Practices (GAA/BAP), and theInternational Standard for Responsible TilapiaAquaculture developed by the World WildlifeFund(ASC/ISRTA).Theobjectiveoftheseauditswas to identify similarities in criteria and areaswhere the standardsdiffered.Thebenchmarking

5


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projectincludedfourtilapiafarmsinChina.Thesefarms represented both small- and commercial-scale production facilities utilising two differentproductionsystems(pondandcages).Asidefromidentifyingsimilaritiesanddifferencesamongcriteriaand requirements used by the three standards,thisprojectalsoidentifiedoutstandingissuesinthefarms,whichmostproducerswereabletoaddressasaresultofthetrialaudit.Todate,allfourfarmsarenowcertifiedunderoneormoreofthecom-mercialaquaculturestandards.

SFP is widely acknowledged for its expertiseby stakeholders in Chinese tilapia, including keyUSandEuropeanbuyersandretailers,aswellasproducers and processors in China, aquacultureinstitutes, industry associations, and localChinesegovernments.GiventhehighleveloftrustthatSFPenjoyswiththetilapiasupplychainitwasappropri-atethatatilapiaAquacultureImprovementProject(AIP)wasofficiallylaunchedin2011.

SFPhasnowinitiatedtworesearchprojectstoassess the impactof tilapia farmingon theexternalenvironment.Thefirstproject,startedinApril2011, involvesmonitoringwaterqual-ityonselected farms inHainanprovince,andwas undertaken by the Hainan Institute ofAquaculture.Dozens ofwater quality param-eterssuchaschemicaloxygendemand(COD),nitrogen and phosphorus content, and heavymetalswereanalysed for five farmsover twocroppings (10 months). The study helped

identifythekeyproblemsandcausesrelatedtowatermanagement.

The second project is an assessment of theregionalenvironmentalimpactsoffishfarmclusters,whichwillbejointlyconductedbySFPandHainanResearchAcademyofEnvironmentalSciences,theleadingenvironmentalresearchinstituteinHainan.Thestudywillexaminethepotential forregionalscaleimprovementbylookingatcarryingcapacityandthepotentialforzoninginaspecificarea.

As more first-hand data becomes available(along with a more in-depth understanding ofexistingpoliciesandmanagementmeasures), theAIPwillestablishaworkinggroupthatconvenesthekeybuyers,suppliersandproducersalongtheChinesetilapiasupply-chaintosharethescientificfindings.TheAIPwillthenformamulti-stakeholderpolicyroundtabletofurtherdiscusstheproblemsandsolutions.TheAIPparticipantswilleventuallyagreeontheactionsandtimetablesnecessarytoachieve the sustainability objectives defined bythegroup.SFPwillplayaleadingroleinengagingstakeholders,providingscientificadviceandfacilitat-ingcommunication.

Up-to-date progressSFPhasworkedcloselywithlocaltilapiaassocia-

tions to assessdifferent tilapia standards that areavailable in the market. A workshop introducingthreeinternationalstandardsfortilapiafarming,i.e.BAP,GlobalGAP, andASC,was held inHaikou

inApril,2011.Over40farmers,processors,tech-nicians and government officers attended theworkshop.Participants found theworkshopveryinformativeandhelpful.Thisenhancedtheproduc-ers’awarenessofincreasingdemandsforcertifiedsustainable seafood from overseas markets, thusfurther facilitating the engagement of Chinesestakeholders into a supply-chaindialogue aroundsustainability.

SFPiscurrentlyworkingwithlocalinstitutesofaquacultureandenvironmentalsciencestoidentifyand evaluate both qualitatively and quantitativelythe environmental impacts of tilapia farming inHainan.Thisincludesanecologicalstudyaswellassocio-politicalanalysistoadviselocalgovernmentsandindustrialassociationsabouthowtoefficientlyaddress theenvironmental issuesassociatedwithtilapiafarminginHainan.ThepreliminaryresultswillbesharedwithkeystakeholdersattheAquaculturePolicyRoundtablethisfallinChina.

SFP is also developing partnerships withChineseuniversitiesandlargefeedmanufacturersto improve feed sourcing for tilapia farming inChina. This work is to be undertaken throughresearch projects on improving feeding efficien-cy and developing alternative feeds with fewerimpactsonwildfisheries.

More InforMatIon:Sustainable Fisheries PartnershipWebsite: www.sustainablefish.org


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VOLUME 15 I S SUE 4 2 012

THE INTERNATIONAL MAGAZINE FOR THE AQUACULTURE FEED INDUSTRY

Tough environment produces world’s best Barramundi

EXPERT TOPIC - Tilapia– a collection of articles creating a worldwide

perspective

Noise– a source of stress for farmed fish

Enzymes– Unlocking the hidden potential of plant

proteins using solid state fermentation technology

Enzymes to improve water and soil quality in

aquaculture ponds

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