May | June 2013

Niacin: one of the key B vitamins for sustaining healthy fish growth and

production

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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46 | InternatIonal AquAFeed | May-June 2013

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In 1951 Dr John E Halver of theSchool of Fisheries Science, Universityof Washington, USA presented the‘model semi-purified fish diet’ to the

aquatic nutrition research community.Thisinnovation allowed for the proliferation ofdeficiency studieswithmainly salmonid fishsuch as rainbow trout and Pacific salmonto evaluate the significance of vitamins incompletedietsforculturedfish.

With such an ‘ideal’ diet, vitamins couldeasily be assayed by using this vitamin testdiet, consistingof ‘vitamin free’ carbohydrateandproteinsourcesi.e.casein,purifiedgelatin,potato starch,hydrogenatedcotton seedoil,alpha-cellulose flour, minerals, cod liver oil,combinedwithcrystallinevitamins.Eachvita-mincouldthenbesystematicallyassessedbyselective exclusion from this advanced basaldiet formulation. The water soluble vitaminssuchastheB-complexandespeciallyvitaminC(ascorbate)wereall found tobeessentialin fishas inother terrestrial animalsofcom-mercial importance and indeed having thesamebasicfunctionsasinhumans.

The role of niacin (vitamin B3) is noless important within aquatic species; as fishfarming became more prevalent, the healthstatusofstocksfluctu-ateddue to thewidespectrumof feed for-mulationsatthattime.A number of nega-tive symptoms wereattributed to niacindeficiency and stepsweretakentoprotectagainstthembasedonearlyevidence.

In the 1940s and1950sfishwerefound

to have a loss of appetite and poor foodconversion(foodintaketobodyweightratio)that progressed into a darker skin colour,anorexia, posterior gut lesions, oedema ofthestomachandintestine,erraticmotionandat-restmuscle spasms. In the late1950sand1960s, a predilection to sunburn in fish wasdiscoveredand, incarp,subcutaneoushaem-orrhagesdevelopedunderchronicandacuteniacindeficiency.

Inthe1970s,eelswerefoundtodevelopskin lesions and display erratic swimming,while lesions, deformed jaws, and anaemiawerediscoveredincatfish,Ictalarus punctatus.Theperiodfrom1980todateencompassedaseriesofinvestigationsthataugmentsearlierknowledge,buttherehavebeenrelativelyfewstudiesintheearly21stcenturyexceptfortheworkofShaikMohammedetal.(2001)wherepathologicaleffectsofniacindeficiencysimilarto thisdescribedabovewerereported fromstudies with Indian catfish (Heteropneustes fossilis).

Metabolic considerations Exogenousproteinswithinthedietsupply

the metabolic pool with essential and non-essential amino acids. Among these is tryp-tophanwhichhasconsiderableimportancein

fish nutrition. In mammals, there is a recog-nised and documented conversion pathwayfromtryptophantoniacin,thusallowingtryp-tophan,andproteinsrichintryptophan,tobeanimportantreservoirforniacinbiosynthesis.

Although the essential amino acid tryp-tophan is a precursor of niacin, this endog-enous synthesis, comprising 13 steps in ametabolic sequence is not deemed efficient.Studiesinmanhaveshownthatapproximately60mgoftryptophanarerequiredtoproduce1mgofniacinandthisratiovariesconsider-ablywithindifferentvertebrategroups.

Fish,however,mayeven lackthisconver-sioncapacityorhaveveryapoorefficacyforthis metabolic pathway. By supplementingboth a niacin deficient and niacin completediet with varying amounts of tryptophan, itwas previously determined that tryptophanlevelshavenoeffectonniacinaccumulation.SerranoandNagayama(1991)foundthatthe3-hydroxyanthranilicacid(3-HAA)topicolinicacid carbolase (PC) activity ratio in rainbowtroutsuggestedanineffectiveconversionfromtryptophan to niacin. This finding will helpexplain higher niacin requirements for somefish, asothersdocarry thecapacity in somedegreebutthiscannotbeaninsuranceagainstproviding a separate dietary supply. Niacin

and niacinamideare required byall living cellsandtheirchemi-cal structureis depicted inFigure1.

They areessential com-ponents of twocoenzymes,niacinamideadeninedinucle-

Niacin: one of the key B vitamins for sustaining healthy fish growth and production

by Simon J Davies and Mark Rawling, Aquaculture Nutrition & Health Group, Plymouth University, United Kingdom

Nicotinic Acid Nicotinamide

Figure 1: Niacin in its two biologically active forms as presented to fish for assimilation

20 | InternatIonal AquAFeed | May-June 2013

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otide(NAD),andniacinamideadeninedinu-cleotidephosphate(NADP)thatareinvolvedin numerous enzymatic pathways especiallythoseinvolvingenergymediationandproteinsynthesis and degradation. More than 40biochemical reactions have been identifiedas being dependent on these coenzymes asco-factors.Theirmajorfunctionistheremovalofhydrogen fromspecificsubstratesandthetransfer of hydrogen to another coenzyme.Reactions in which NAD and NADP areinvolved include themetabolismof carbohy-drates, lipidsandproteinsat thecross roadsofmetabolismandvitalforenergyproductionfromthesenutrientsandproteinturnover.

With respect to genomic stability, theneed for niacin seemsmost imminentwhenthe organism is under genotoxic or oxida-tive stress, with particular reference to UVexposureoftheanimal(Hageman&Stierum,2001).Adeficiencyofniacinwill result inanincrease or disrepair of DNA nicks withinchromosomes, and consequent increase inchromosomal breakage, and a heightenedsensitivity to mutagens (Fenech, 2002). Ingeneral, fishwithniacindeficienciesdisplayedanincreasedriskofsunburnwhenunderevennaturalUVradiation.

In the expanding aquaculture industry,

feedconversionratiosmustbe optimised in order forproductioncoststobemin-imised. Greater efficiencypresent throughout cultur-ing conditions will lead toshorter growing timeandagreater demand for micro-nutrients such as vitamins.Surplus nutrients, such asvitaminssuppliedabovelev-elsusefultothespecies,canberemovedfromthedietifexactrequirementsaremet.

In thepast,manyvitaminshavebeen included inexcessofrecommendedlevelstobecertain that therequirementswere fully complied (NRC2011).However,studieshave

reported excess niacin can inhibit growth(Poston&Lorenzo,1973;Poston&Combs,1980); conversely, sub-optimal absorptionofnutrientscanbeavoided if requirementsarecorrectly defined and adequately presentedinfeed.Formaximalefficiencyofproduction,target provisions of all essential nutrients, asspecifiedthroughresearch,mustbeprovidedthrough additional mineral and vitamin sup-plementation. If levels are unknown, furtherresearch is needed to clarify the degree ofvitamin fortification necessary to maintainhealthandproductionforallphasesofrearingandconditions.

In relation to the other water-solublevitamins, niacin requirements in fish procurea ranking amongst the highest needs, withtheexceptionofcholine(NRC,2011).Whilemany other vitamins are synthesised fromprecursorcompoundsobtainedthroughfeedingredients,inaquaticanimals,niacinisusuallyobtained solely through niacin presented inthediet.

Niacin requirementsCaution must be expressed due to the

variety of methodological approaches usedin ascertaining vitamin requirement levels. Inmanycases,ageandgeneticstrainofthespe-

cies varies together with the pre-nutritionalhistoryoftheaquaticanimalunder investiga-tion. Inparticular,thenatureofthecarbohy-drate component employed in experimentaldiets is not fully reported in the scientificliterature. Forexample, it iswell known thatthe carbohydrate level and complexity mayinfluence the requirement of niacin in termsofprocessingofdietaryenergy(Shiau&Suen,1992).Thismaybeevidentwhenrawmateri-als are subjected to extrusion processing inwhichcarbohydratessuchasstarchincerealsmay undergo gelatinisation yielding dextrinand thereby increasing the digestible energyvalue of the carbohydrate fraction. It wasfound that for hybrid tilapia that the niacinrequirementsforfishfedglucoseordextrinasthe carbohydrateenergy sourcewas26 and125mg/Kgdietrespectively.

Previous formulations of fish diets oftenfailed to address the true bioavailability ofmicronutrientspresentinfishfeedingredientspursuant to a limited common databasedescribingthisknowledge.Thegeneralniacinrequirements fordifferentspeciesareshownin Figure 2 and these vary considerablydependingonmany factors.Dietary require-mentshavebeenreportedtorangefromjust1-5mgper kg of feed for rainbow trout to150-200mgforpacificsalmonand14mgperkgforchannelcatfish.

Clearlymuchwilldependonthecarnivo-rous, omnivorous or herbivorous nature ofthefishspeciesinquestionandrearingcondi-tions. Investigations on Gilthead sea bream(Sparus aurata)byMorrisandDavies(1995)andbyMorrisetal.(1995),wherethequali-tative and quantitative requirements for thisimportant marine fish were first establishedusing semi-purifieddiet ingredients similar totheHalverconcept.

The minimum nicotinic acid requirementforseabreamwasdeterminedtobe52mg/Kg toachieveoptimumgrowthperformanceand25mg/kgfornormalhaematologicalbal-anceandlivertobodyweightratio.

In 1997, Shiau reported parallelismbetween the niacin requirement of warmwater fish and a varying source of dietary

Figure 2: Niacin requirements for selected aquatic animal species (from compiled literature sources)

20 | InternatIonal AquAFeed | May-June 2013 May-June 2013 | InternatIonal AquAFeed | 21

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carbohydrate. In general, certain warmwater fish, namely carnivorous species, uti-lise dietary carbohydrate poorly and itis recognised that carbohydrate obtainedfrom different sources may not be equallyavailable to all fish of the same species.There is merit for consideration of thechangesinproteinlevel,quality,andproteinto energy ratio for optimumvitamin levelstoberecommended.Modernfishdietsaremuchhigher inenergy,presentedasoil forcarnivorous fish,whilstcarbohydrate in theformofstarchisquiteacceptableforomni-voressuchastilapiaandcarp.Niacinisgivenspecial importance in this area due to itsrelevancyinthemetabolismofproteinandthe releaseof energy from these nutrientsasstatedpreviously.

However implications towards dietaryrequirement and variability, warrants a needto establish additional scientific informationregarding the digestibility of niacin and sub-sequent availability coefficientswithin varyingdiets formulations based on practical ingre-dients.

FromthedataofNgetal.(1998),itwassuggestedthatniacinsupplementationcanbereducedtoamoreefficientlevelduetotherelativelyhighamountofbiologicallyavailableniacin found in typical feed ingredientsusedinmodern fish feed formulations.However,the provisions may not be adequate to

meet current safety margins to guaranteeproduction and health criteria for all spe-cies. Also, the inability to utilise particularfish feedsdue to varyingdietary constraintswouldjustifycontinuedsupplementationandrefinement.Inaddition,itwasfoundthatthebioavailability of niacin increased by some57 percent when corn meal was extrusioncooked rather than administered in thediet in its native form. This suggests thatprocessing technology is an important areafor further investigation fordetermining theoptimuminclusionlevelsofniacinforarangeofaquaticspecies.

Stability and processing lossesNiacinisregardedasahighlystablevitamin

in animal nutrition and is usually added tofeed as nicotinic acid or nicotinamide withinthevitaminpremix formulationswithinadrymixture with a carrier material along withother vitamins and possibly mineral supple-mentsaswell.

The advent of high energy and nutrientdense feeds in many countries engaged inintensive fish farming operations has alsoplaced a higher burden on maintaining thehealthoffish,whilstpromotingfastergrowthrates and efficient feed utilisation. The useofexpandedandextruded feedsoffermorescopeinfeedingmanagementbutmaygreatlyinfluence the levels of vitamins available to

fish under various conditions. Extrusion ofdietshasthetendencytoreducetheactivityof vitaminsespecially thosewithin thewatersolubleclassandtheprocessingofrawmateri-alsmayleadtoseriouslosses.Generallythisisin theorderof10-20percent formostvita-mins reported (Tacon, 1985, Gabaudan andHardy, 2000). Further reductions are causedbystorageofpelletedfeedandthismayresultin impairment to fish health and productionefficiencyoverextendedtime.

Future perspectiveIndeed, the movement towards new fish

species in aquaculture such as flounders;turbot, sole and halibut as well as sea bassand sea bream in Europe, cobia in theUSAandBrazil have generated considerableinterest in producing specific diets that canmeettheirindividualrequirementsforgrowth,development and health. Much is knownabout the gross nutritional requirements oftheseemergingspeciesbut littleonvitamins,especially niacin. Intensive rearing conditions(i.e. UV light exposure to outdoor pens)andhusbandry related factorsmay adverselyaffect the physiological status of fish andinduce metabolic stress causing tissue dam-ageandimpairedperformance.Thepotentialof niacin supplementation in reducing sucheffectscouldproveavaluableareaforfutureinvestigation.

22 | InternatIonal AquAFeed | May-June 2013

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May-June 2013 | InternatIonal AquAFeed | 23

Itisevidentthatthevitaminrequirementsof fish are subject to numerous factors.Recent advances in our understanding ofaquatic animal biochemistry and physiologytogether with aquafeed technology increasethe advantageous value of a thorough re-examination of the vitamin requirements offish. This is particularly pertinent for niacingivenitsroleinaquaticanimalnutrition.Thereisapaucityofinformationintheliteratureforniacininfishcomparedtoothervitamins,andthismatterneedstobeaddressedinthelightofnewcandidatespeciesforaquacultureandchanging feed formulations where plant byproductsareincreasinglybeingincorporated.

Selected References

Fenech,M.(2002).“GenomicStability:anewparadigmforrecommendeddietaryallowances(RDA’s).”FoodandChemicalToxicology.vol.40.pp1113-1117.

Gaubadan,JandHardyR.W.(2000).Vitaminsourcesforfishfeedspp,961-965InEncyclopaediaforAquaculture,R.R.Stickney,Editor,NewYork,JohnWileyandSons,Inc.

Hageman,G.J.andStierum,R.H.(2001).“Niacin,poly(ADP-ribose)polymerase-1andgenomicstability.”MutationResearch.–FundamentalandMolecularMechanismsofMutation.vol475.nos1-2.pp45-56.

Halver,J.E.(1957).“Nutritionofsalmonidfishes:3.

Water-solublevitaminrequirementsofChinooksalmon.”JournalofNutrition.vol.62.pp.225-43.

Halver,J.E.,(Halver,J.E.andHardy,R.W.(Editors).FishNutrition.3rdEdition.Oxford:AcademicPress,2002.

Morris,P.C.andDavies,S.J.(1995)Therequirementofthegiltheadseabream(Sparus aurataL).fornicotinicacid.AnimalScience,61:437-443

Morris,P.C.Davies,S.J.andLowe,D.M.(1995)QualitativerequirementsforBvitaminindietsforthegiltheadseabream(Sparus aurata)AnimalScience,61;419-426.

Ng,W.K,Serrini,G.,Zhang,ZandWilson,R.P.(1997)“NiacinrequirementandinabilityoftryptophantoactasaprecursorofNAD+inchannelcatfish,Ictalurus punctatus”Aquaculture.vol.154.nos.1-4.pp273-285.

NRC(2011)“NutrientRequirementsofFish,”NAS/NRC,AcademicPress,WashingtonD.C.

Poston,H.A.(1969)“Theeffectofexcesslevelsofniacinonthelipidmetabolismoffingerlingbrooktrout.”In:FisheriesResearchBulletin,Albany,N.Y.:StateofNewYorkConservationDepartment.no.32.pp.9-12.

Poston,H.A.andDiLorenzo,R.N.(1973)“Tryptophanconversiontoniacininthebrooktrout(Salvelinus pontinalis).”Proceedings.SocietyforExperimentalBiologyandMedicine.vol.140.pp.110-12.

Poston,H.A.andCombs,G.F.(1980)“Nutritionalimplicationsoftryptophancatabolisingenzymesin

severalspeciesoftroutofsalmon,”Proceedings.SocietyforExperimentalBiologyandMedicine.vol.163.pp.452-454.

Poston,H.A.,andWolfe,M.J.(1985).“Niacinrequirementforoptimumgrowth,feedconversionandprotectionofrainbowtrout,Salmo gairdnerifromultraviolet-Birradiation”JournalofFishDiseases.vol8.no.5.pp.451-460.

Serrano,A.E.andNagayama,F.(1991).“Liver3-hyroxyanthranilicacidoxygenaseactivityinrainbow-trout(Oncorhynchus-mykiss).”ComparativeBiochemistryandPhysiologyB-Biochemistry&MolecularBiology.vol.99.no.2.pp.275-280.

ShaikMohammed,andIbrahim,A.(2001)QuantifyingtheniacinrequirementoftheIndiancatfish(Heteropneustes fossilis)(Bloch),fingerlings,AquacultureResearch,32:157-162.

Shiau,S.Y.,andSuen,G.S.(1992)“Estimationoftheniacinrequirementsfortilapiafeddietscontainingglucoseordextrin.”JournalofNutrition.vol.122.no.10.pp.2030-6.

Tacon,A.G.J.(1985)Nutritionalfishpathology:morphologicalsignsofnutrientdeficiencyandtoxicityinfarmedfish.”AquacultureDevelopmentandCoordinationProgramme.ADCP/REP/85/22.

More InforMatIon:Email: simond@aquafeed.co.ukWebsite: http://www.plymouth.ac.uk/pages/view.asp?page=32557

22 | InternatIonal AquAFeed | May-June 2013 May-June 2013 | InternatIonal AquAFeed | 23

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Niacin – one of the key B vitamins for sustaining

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