ON-FARM MYCOTOXIN CONTROLIN FOOD AND FEED GRAIN

ON-FARM MYCOTOXIN CONTROLIN FOOD AND FEED GRAIN

training manual

1GOOD PRACTICES FOR ANIMAL FEED AND LIVESTOCK

Mycotoxins are among the most potent causes of cancer. Ingestion through the diet can pose chronic health risks for both humans and livestock. Death may occur as a result of acute poisoning. Mycotoxins are chemicals produced by fungal moulds. These moulds grow during production, harvesting and storage of grain, pulses, nuts, roots and other crops.

This booklet is directed at the farm situation, providing advice that can be used to avoid mycotoxin contamination before food leaves the farm. The booklet describes what mycotoxins are, how they are produced and how to recognise signs of their presence. It provides advice to enable farmers to minimise the risk from mould contamination whilst the crop is growing, during harvest and through storage. Although aimed at farm situations, the booklet is intended to be used by extension personnel, both government and non-government employees, in their efforts to advise and assist the rural communities. A separate booklet addresses issues related to transport, marketing and urban consumption.

ON-FARM MYCOTOXIN CONTROLIN FOOD AND FEED GRAIN

training manual1GOOD PRACTICES FOR ANIMAL FEED AND LIVESTOCK

Rome, 2007FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS

Peter Golob

The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations (FAO) concerning the legal or development status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. The mention of specific companies or products of manufacturers, whether or not these have been patented, does not imply that these have been endorsed or recommended by FAO in preference to others of a similar nature that are not mentioned. The views expressed in this information product are those of the author(s) and do not necessarily reflect the views of FAO.

ISBN 978-92-5-000000-0

All rights reserved. Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders. Applications for such permission should be addressed to:ChiefElectronic Publishing Policy and Support BranchCommunication DivisionFAOViale delle Terme di Caracalla, 00153 Rome, Italy or by e-mail to:copyright@fao.org

© FAO 2007

iii

Contents

Preface vAcknowledgements viGlossary vii

whAT ARE myCOTOxINS? 1 Signs of mycotoxins and mould growth 1 Factors that affect fungal growth 2 Climatecharacteristics 3 Otherfactors 3 what are the effects of mould on animal feed? 4 which moulds produce mycotoxins? 4 what are the symptoms of mycotoxin poisoning? 7 Humans 8 Cattle 8 Poultry 9 Pigs 9 Sheepandgoats 10 Horses 10 Generaleffectsofmycotoxins 10

hOw TO TAkE CARE OF FOOD AND FEED 13 Prevent mould damage before harvest 13 Prevent mould damage during harvest 15 Prevent mould damage after harvest 17 Drying 17 Threshing,shellingandwinnowing 18 Storage 19

Unthreshed produce 19Threshed produce 20

Instore 22 Storingflourandcompoundedfeed 22 Silageandhay 23 Disposal of mycotoxin contaminated grain 24

REFERENCES 27

v

Whenweeatfoodthatwehavegrownorboughtweareunwittinglyconsumingmanysub-stancesotherthanthebasicnutrientswhichweassumemakeupthefooditem.Thesameappliestothefeedweprovideforourdomesticatedanimals.Manyforeignsubstancesareaddedbymantoimprovequalityandpreventbiologicaldecay,theseincludeinsecticides,colourants,minerals,vitaminsandpreservatives.However,therearemanymaterialsthathaveadamagingeffectandarenotaddedbyman,butaretheresultofinfectionsbyotherorganisms.Forexample,foodscancontainbacteriathatgrownaturallyonproduceandwhichmayleadtofoodpoisoningifingested.Otherharmfulsubstancesmaybepickedupasaresultofenvironmentalpollution,suchasundesirablepesticidesandheavymetals.

Onegroupofundesirablesubstancesaremycotoxins.Forthemostpart,theirpresenceisbeyondthecontrolofmanandcanleadtosevereharmfuleffectsinbothhumansandlivestock,culminating,insomeinstances,indeath.Mycotoxinscanbeproducedthrough-outthegrowingcyclebutpredominatelyafterthecrophasmaturedinthefield,throughtheharvestandstorageperiods.Theirpresenceaffectsfarmers,theirfamiliesandlive-stock,aswellasconsumersintownandcitieswhomayingestcontaminatedproduce.

Thisbookletisdirectedatthefarmsituation,providinginformationthatcanbeusedtoavoidmycotoxincontaminationbeforefoodleavesthefarm.Aseparatebookletaddressesissuesrelated to transport,marketingandurbanconsumption.Although it isaimedatfarmsituations,thebookletisintendedtobeusedbyextensionpersonnel,bothgovern-mentandnon-governmentemployees,intheireffortstoadviseandassistruralcommu-nities.Itisnotatreatiseonmycotoxinsandfungibutratherprovidespracticaladvicetocombattheproblem.Itisexpectedthatthoseusingthisbookletwillhaveabasicknowl-edgeofbiologyandofagriculture,bothproductionandpost-harvest.

The first sections describe what mycotoxins are, how they are produced and how torecognisesignsoftheirpresence.Thebookletisparticularlyconcernedwithrecognisingthepresenceoffungalmouldsandprovidesadviceonhowtopreventmouldsfromgrow-ing.Thelatterhalfofthebookletprovidesinformationtoenablefarmerstominimisetherisk frommouldcontaminationwhilst thecrop isgrowing,duringharvesting,and thenafterharvest,i.e.whenthreshing/shelling,andstoringthecrop.Italsoexaminesactionstotakewhenstoringflourandfeed,silageandhay.

Preface

vi

Acknowledgements

IwouldliketothanktheNaturalResourcesInstituteUKandtheFungalResearchTrustforallowingmetoreproducephotographsfromtheircollections.IwouldliketothankTanyaStathers for the informationon theavailabilityof resistant varieties inEastAfrica, andProfessorRayCokerforinformationonvariousissuesrelatingtomycotoxinproblems.

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Glossary

Aflatoxicosis (aflatoxicoses: plural) diseases resulting from consumption of aflatoxins

ATA alimentary toxic aleukia, a mycotoxin disease in humansDON deoxynivalenol (a mycotoxin)ELEM equine leukoencephalomalacia, a disease of horsesMetabolite a substance produced as a result of a chemical change occurring

during a biological process, such as respiration, photosynthesis in plants, cell growth etc.

Mycotoxicosis (mycotoxicoses: plural) diseases caused by ingestion of mycotoxinsOTA ochratoxin A, a member of the ochratoxin mycotoxinsppb parts (of the active substance) per billion (parts of the target: body

weight or grain weight)PPE porcine pulmonary oedema, a disease of pigsT-2 a trichothecene mycotoxin

1

Mycotoxins are among the most potent causesof cancer. Ingestion through the diet can posechronichealthrisksthatmayresult inliverandkidneydiseaseandasuppressionoftheimmunesystem.Deathmayoccurasaresultofacutepoi-soning. In livestock,mycotoxinscanalsomodifythenutrientvalueandthereforethemetabolismoffeed,andalterthehormonalbalance.

Mycotoxinsarechemicalsproducedby fungalmoulds. These moulds grow during production,harvesting or storage of grains, pulses, nuts,roots and other crops. As the moulds develop,theyproducedifferentchemicals,someofwhichenable the fungal colonies to grow and multi-ply but others, including mycotoxins, appear toprovidenoobviousbenefit to themoulds (someof these chemicals are actually beneficial tomanasinthecaseofantibiotics,likepenicillin).Mycotoxinsareknownas‘secondarymetabolites’astheyhavenodirecteffectonthedevelopmentof the mould, though they do give it an advan-tage over competing organisms, such as othermoulds, yeasts and bacteria. These toxins, orpoisons,disruptcellstructuresandinterferewithvital cellular processes, allowing the mould tocompetesuccessfullywithotherorganisms.Theyalso cause problems for humans and animalsthatingestthem.Wewillseejusthowdangerousthesechemicalscanbe.

Notallmouldsproducemycotoxins.Notevenall strains of a species of mould that producesmycotoxins are able to do so. Nobody is awareof theprecise factors thatdeterminewhetheragrowingmouldwillproduceamycotoxinornot.Itis,therefore,notpossibletoanticipatewhetheramouldgrowingonacropwillreleasemycotoxin,butitisalwaysbettertoassumethatitwilldoso.Itisbettertobesafethansorry!Bydoingso,thechance of coming into contact with highly toxicsubstancescanbereducedoravoided.

What are mycotoxins?

Themostcommonmycotoxinsknowntocausehealthproblemsinmanandlivestockare:

• Aflatoxins• Fumonisins• Trichothecenes, especially T-2 toxin also

knownasvomitoxin• Deoxynivelenol(DON)• Ochratoxins,especiallyochratoxinA(OTA)• Ergottoxins• ZearalenoneSome of the other toxins which may affect

healtharelistedinTable1.

SiGnS of mycotoxinS And mould GroWthMycotoxins are not visible to the eye. Grain thatshows no signs of mould infection may be con-taminatedwithmycotoxin.Thesemetabolitesmaybe found on apparently uncontaminated grainsthatare incloseproximitytootherswhichshowsignsofmouldgrowth.Whenafarmersortsgraintobesoldandremovestheobviouslydiscoloured,mouldygrain,evengrainwhichshowsnosignsofmouldgrowthmaynonethelessbecontaminatedwithmycotoxins,andthusfinditswaytothelocalmarket. However, this risk of contamination isrelatively low, and for practical purposes, grainthatdoesnotshowsignsofmouldinfectioncanberegardedasbeingfreeofmycotoxin.

Mouldsgrowingongrainandothercommodi-ties are generally clearly visible. They are oftencolouredandaffecttheappearanceoftheproductonwhichtheyaregrowing.Produceinfectedwithmouldtakesonanunappealingsmell.

Physical signs of mould in animal feedinclude:

• Dustiness• Caking• Poorflowoutofgrainbins• Feedrefusalbyanimalsfornoapparentrea-

son

on-farm mycotoxin control in food and feed grain2

• ‘Mouldy’andmustysmell• Darkeningoffeedandgrain

The presence of mould has a major impact onthequalityofgrain.Nobodywantstoeatmouldyfood.Farmerswillnotallowmouldygraintobeusedinthepreparationoffoodfortheirfamilies,unlessthereisasignificantfoodshortage,suchas when a famine occurs. Mould-contaminatedgrain is often discarded, is certainly difficult tosell,andwilleithercausegraintoberejectedorat best, downgraded with a loss in value. How-ever,mouldygrainisusuallyretainedforbrewingbeerorisfedtolivestock.Wewillseelaterwhyfeedingpoultry,pigs,goats,cattleandanyotherlivestock with mouldy grain can seriously affectthehealthoftheanimalsandbecounterproduc-tive.

fActorS thAt Affect funGAl GroWthFungalinfectionoffoodcommoditiescanoccur:duringplantgrowth;oncetheplanthasmatured;during harvesting, drying and storage; duringprocessing;andevenwhentheprocessedprod-uct is waiting in the trader’s store or on theconsumer’s shelf. Mycotoxin production, simi-larly,canoccuratallthesestages,fromseedtoshelf. Fungal growth and mycotoxin productionare particularly influenced by moisture, tem-peratureandoxygencontent.Furthermore,grainandotherfoodcommoditiesthataredamagedorstressed by drought, pests, and cultivation and

harvesting practices, are more susceptible tomouldgrowth.

Fungi multiply by releasing spherical spores.These germinate producing elongated projec-tions known as hyphae. Hyphae multiply andbranch and form a mass of fungal tissue, themycelium, at which stage it is recognisable asmould.

fiGure 2A

Spores

Sporegermination

MyceliumForms: mould

Hyphae elongateand branch

fungal life cycle (Aspergillus)

fiGure 1 mouldy groundnut (a), cassava (b) and millet (c)

(a) (b) (c)

3What are mycotoxins?

climate characteristicsMouldsrequirewaterforgrowth,reproductionand other biological processes. The amountof water in a plant or seed that is availableto support these processes is known as its‘wateractivity’. A minimum water activity of0.70 will sustain growth of storage moulds,though for field moulds that produce myco-toxins water activity should be above 0.85.Water activity is similar to moisture con-tent but is dependant on temperature andthechemicalcompositionof thecommodity.Thustheambienttemperaturewhichaffectsthetemperatureofthegrainandthetypeofcommodity,whetheritacowpeagrain,freshtomato, groundnut pod or maize cob willaffecthowamouldwillgrow.Forevery10°C,wateractivityrises0.03.

The amount of moisture that is containedin air is known as the humidity. As air getswarmeritiscapableofcarryingmorewater;so humidity increases. The water in the airis in a state of balance with that containedingrainsandotherfoodproducts.Whentheair contains about 70%moisture, at a tem-peratureof27°C,mostcerealgrainswillbeable to hold 13-14% moisture; groundnutswill hold about 7% because of their high oilcontent. If the temperature then decreases

theairwillgiveupsomeofitswater,whichwillbe picked up by the grain. Conversely, if thetemperatureincreasestheairwilltakemoisturefrom the grain and the grain moisture contentwilldecrease.Therelationshipbetweenwaterintheairandmoisturecontentofgrainistherela-tivehumidity.Asaverygeneralruleandapproxi-mateguiderelativehumidity isabout100 timesgreaterthanwateractivity,soarelativehumidityof70%willequatetoawateractivityofmaizeof0.70whenthetemperatureisabout25-30°C.

Most mycotoxin-producing fungi require therelative humidity to be above 70% in order forthem todevelop.So forwheat,maize, sorghumandmilletsstoredinthetropicsandsub-tropicsa relative humidity of 70% will allow the grainsto be kept safely without problems of mouldcontamination, as long as the moisture contentofthegrainitselfisat13-14%forcerealsand7%forgroundnuts.Ifthemoisturecontentformaizeforexample,is20%,thegrainwillnotbesafetostoreandmouldswillgrow.

Farmers cannot influence the moisture car-riedintheairortheambienttemperature.Theymay,however,influencetheamountofmoistureintheirgrainbydryingit.Theyhavetoforcefullyexpel water and so upset the natural balancebetween the environment and their commod-ity. Where the climatic conditions are hot andhumid, artificial drying may be the only way toreducegrainmoisturecontenttopreventmouldgrowth.Indryerclimatesthiswillbemoreeasilyachievedbecausethegrainwillnaturallyreleasewaterintothedryairuntilabalanceorequilib-riumisreached.

other factorsMycotoxin-producing moulds attack crops bothbeforeandafterharvest.Pre-harvestfungalinva-sion is influencedby in-fielddamagecausedbyinsects,birds,rodents,husbandrypracticesandadverseweather.Stresscausedbydrought,nutri-entdeficiencyanduntimelyorexcessivefertiliserapplicationmayalsopredispose towards fungal

fiGure 2b A. flavus mycelium (b)

on-farm mycotoxin control in food and feed grain4

establishment. Cracked grain may be readilyinvadedbyair-borne,fungalspores.Maizecobs,heads of sorghum and millet, pods of legumecrops such as groundnuts, beans and cowpeasthatfalltothegroundmaybereadilyinvadedbysoilordetritusbornespores.Repeatedplantingof the same crop in the same or nearby fieldsfavours fungal infection by increasing both thefungalinnoculumandtheinsectpopulationthatattacksthegrowingcrop.

Poorhandlingatharvest,duringcarriagefromthe field, whilst threshing and winnowing andduring storage will similarly assist to encour-age mould. Post-harvest pest attack, especiallyby insects, will make grain more susceptible toentry by fungal spores, and the production ofwaterasaresultofinsectrespirationwillenablethese spores to germinate and form mycelialclusters.

WhAt Are the effectS of mould on AnimAl feed?Mouldyfeedsarelesspalatableandanimalsmayeatless.Thiswillleadtoareductioninnutrientintake and so decrease weight gain and milkproduction.Evenifmycotoxinsarenotproducedithasbeenestimatedthatthepresenceofmouldalonewillcausealossinperformanceof5-10%.

Mouldyfeedmaynotbeasdigestibleandtheenergy content will therefore be reduced. Fur-

thermore, the mould itself will use the protein,carbohydrate and fat from the feed for its owndevelopment,reducingthatavailabletotheani-mal.Fatintake,especially,isreducedinmouldyfeedandenergyavailabilitymaybereducedbyasmuchas10%

Moulditselfmaycausehealthproblems,espe-cially respiratory disease. Breathing in mouldspores for example, causes farmer’s lung inman.

NumeroushighlytoxigenicspeciesofAspergil-lus, Penicillium and Fusarium have been foundindamphayandstraw.Asaresult,alargerangeoftoxinsincludingpatulin,aflatoxinsandsterig-matocystin can be found in insufficiently driedhayandstraw.Instore,thesemouldscontinuetobepresentformanymonths.

Which mouldS Produce mycotoxinS?There are more than 300 known mycotoxinsbut we know very little about most of them.This manual focuses on the most common andimportantofthese.Themainmycotoxinproduc-ingspeciesareshowninTable1.

The genus Fusarium, which is a pathogenoccurring during plant growth, produces morethan70differenttoxinsofwhichthemostimpor-tantarefumonisins,deoxynivalenol(DON),zeara-lenone and trichothecenes, which include T-2toxinorvomitoxin,toxinsthathaveonlyinrecentyears begun to be studied in depth. Some spe-ciesofFusariumcanproduceup to17differentmycotoxinssimultaneously.

Fusarium is responsible for head blight andscabinwheatandbarleyandearrotinmaizeincereal growing areas of Africa, Asia and Northand South America. It can also be found onforage in the field. Fusarium species generallyrequireawateractivityofabove0.88 todevelopso are rarely carried over in to stores afterharvest, though they it may still develop on thestandingcropifharvestoccursduringperiodsofrainfall. However, although the mould may not,

fiGure 3 mould growing in a chicken’s lung

5What are mycotoxins?

itself,becarriedoverintothestorethemycotox-insitproducesmaywellbe.Fusariumverticillioi-desandF.pallidoroseumpredominateoncerealsinthetropicsandsub-tropics;F.graminearium,perhapsthemostcommonofthegenus,prefershumid-temperate conditions, which do occurin many parts of sub-Saharan Africa and LatinAmerica.Fusariumtoxinsarenotapparentlycar-riedoverintomeat,milkoreggs.

Themostcommon,importantandwidelystud-ied mycotoxins in tropical and semi-tropicalareas are those of the aflatoxins complex, pro-duced by Aspergillus, a post-harvest mould.There are several different aflatoxins; B1 is themost toxic. The other post-harvest genus ofimportance isPenicillium. Higher temperatures and humidities in the tropics mean that boththesemouldshavespecies that candeveloponcropspre-harvest,oncethegrainshavebeguntodry,sometimescausingsignificantdamage.Forexample, A. flavus and A. niger cause ear rotsofmaizeandA.flavuscanproduceaflatoxinsinthe field.Earrot infectionandaflatoxinproduc-tionstartinginthefieldcancarryoverintostore. P.verrucosum produces ochratoxin A (OTA) asdoesA.ochraceus.

SlowdryingofgrainsandoilseedsafterharvestcanallowthecontinuedgrowthofA.flavus andarapidriseinaflatoxinconcentration.Ifthecom-modityisimproperlydriedorallowedtobecomewet after drying a succession of fungi can theninvadethegraindependantonthewateractivity.SpeciesofEurotium arethemostcommonearlyinvaders of improperly dried grain, leading to alossofgerminationandquality.AsuccessionofAspergillusandPenicilliumspecies then invadeif the water activity is high enough. Species offungi from these three genera are the mostfrequently isolatedorganisms frommoststoreddurablecrops.

Mould and mycotoxin problems are unlikelyto occur if storage takes place mainly duringdryperiodsof theyear.Criticalperiodsforcon-taminationare:attheendofthegrowingseason;

fiGure 4 Aspergillus ear rot (a) and fusarium ear rot (b)

(b)

(a)

when the crops are mature and begin to dry;during harvesting; and during the first monthsimmediately after the harvest is brought to thefarm. At maturity, when the plants begin to dieback,continuousrainwillslowthedryingprocessand facilitate the development of Fusarium andproduction of its mycotoxins. Colonies of thesefungimaywellbecarriedoverintothestoreandcontinuetogrowiftherelativehumidityremainselevated.Prolongationoftherainsduringharvest–cropscanremain in the field formanyweeksbefore being removed for storage – similarlyprovides ideal conditions for many post-harvestfungiandparticularlyforAspergillus.Duringtheearlymonthsofstorage,whengrainmayhaveamoisture content of 20% (water activity of 0.8+)or higher, fungal development will occur in themoistcropunlessitisdriedrapidly.

on-farm mycotoxin control in food and feed grain�

TABLE 1 mAjOR myCOTOxIN PRODUCING GENERA

fungi mycotoxin pre or post harvest climatic requirements

food commodities contaminated

comment

Fusariumverticillioides(moniliforme),F.proliferatum

Fumonisin Pre-harvest Cosmopolitan Wheat,maizeandproducts,hay

Verystable,cansurvivecooking,solublecanberemovedbywetmillingandnixtamalisation

F.graminearium Deoxynivalenol(DONorvomitoxin)

Pre-harvest Cosmopolitan Wheat,maize,millet,hay(zearalenone)

Verystable,cansurvivecooking,solublecanberemovedbywetmilling;nottransferredtomilk,meatoreggs

F.graminearium Zearalenone

F.graminearium,F.culmorum,F.poae

Trichothecenes Pre-harvest Temperatetocold Wheat,maize(overwintered),hay

Verystable,cansurvivecooking

F.sporotrichioides T-2toxin

Aspergillusochraceus

OchratoxinA Post-harvest Warm,humid Cerealsandcerealproducts,pulses,driedvinefruit,beverages,spices,groundnuts

Hasbeenfoundinpigmeat

Penicilliumverrucosum

OchratoxinA Post-harvest Temperate

Penicilliumsp.,Aspergillussp.

Citrinin

Penicilliumsp.,Aspergillussp.

Cyclopianzonicacid

Aspergillussp. Sterigmatocystin

Clavicepspurpurea Ergot Pre-harvest Mainlytemperate cereals

Various Patulin Post-harvest Mouldyfruit,vegetables,cereals,otherfoods.

Destroyedbyfermentation

Aspergillusflavus,A.parasiticus

Aflatoxins(B1,B2,G1,G2,M)

Mostlypost-harvest Tropicalandsub-tropical

Maize,wheat,groundnuts,otherediblenuts,figs,spices,soyabean,cottonseed,oilpalmkernels,copra,coconutoil,cassava

Mouldsdonotgrowinsilagebutaflatoxinscansurviveensilingprocess.

Fusariumtoxinsareapparentlynotcarriedoverintomilk,meatandeggs(M.E.Doyle(1997):http://www.wisc.edu/fri/fusarium.htm:5).AlthoughfumonisinsandDONarenotthemosttoxicoftheFusariumtoxinstheyarethemostfrequentlydetectedandthereforethemostassociatedwithhumanandanimalillness(thisappliestoUSinparticularandmaybealsoEurope,butmaynotberelevantforAfrica).

Othermycotoxinproducersincludingthegrow-ingcropsClavicepspurpurea(ergot).Thisfungusproduces toxic alkaloids from dark brown toblack bodies (sclerotia or ergots) that stick outfromtheseedheadofinfectedplants,commonlycereals and especially rye. Ergots are visible to

thenakedeyeand look likeratdroppingswhenremovedfromtheseedhead.Theymaygrownupto2.5cminlength.Ingestioncanresultin‘ergot-ism’, neurological disorders, including tremors,staggers,convulsionsandnecrosis,andgangre-nousdisorderssuchassloughingofthehoofor

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feetandtailaswellasdrygangrene.Acessationofmilkproductioninpost-partumfemalesisalsocommon.

Another important genus is Stenocarpella(Diplodia), which causes stem and ear rots inmaize.Thecompositionofitsmycotoxinsareasyetunknownbuttheeffectscanbesevereinlive-stock.MycotoxinsofS.maydiscausediplodiosisincattle,symptomsofwhicharelossofco-ordi-nation, nervous system defects, paralysis anddeath. In sheep, diplodiosis causes abortions,and in poultry reduced egg laying and growth.It isnotknownwhether thesemouldshaveanyeffectonhumans.

Some other disease causing fungi includeNeotyphodium,whichcausesdrygangrene,andRhyzoctonia, which produces slaframin causingsialorrheaorexcessivesalivationinruminants.

WhAt Are the SymPtomS of mycotoxin PoiSoninG? In livestock, aflatoxins B1 and M1, ochratoxin A(OTA)andsterigmatocystinhavebeenfoundtobecarcinogenic.Inhumans,aflatoxinsandOTAhavebeen classified as carcinogenic, and fumonisinB1asapossiblecarcinogen.Patulin,atoxinpro-duced by both Aspergillus and Penicillium spe-

ciesonfreshfruit,andwhichoccursparticularlyinfruitjuices,isalsoahealthhazard.

The effect of mycotoxins on animal produc-tion is influencedby the typeandconcentrationof toxins present; the exposure period; the ageand typeofanimal;and itsnutritionandhealthstatus.Mycotoxins tendnot toberecognisedbythebody’sdefencemechanismsothatantibodiesarenotproduced inresponsetotheir ingestion.Thustheeffectsofmycotoxinpoisoningareoftenchronicandgradual,somakingitfrequentlydif-ficult to diagnose or monitor the effects beforesymptomsbecomesevere.Thesituationismadeworse because more than one mycotoxin maybe present; for example aflatoxins and sterig-matocystinmaybeproducedatthesametimebyAspergillusflavus.

In man and animals mycotoxins target dif-ferent organs. The following is a summary ofwhichorgansinthebodyandwhichphysiologicalsystemsareattackedbydifferentmycotoxins (itmust not be assumed that ingestion of thesetoxins will always have the same effect as thedosage ingested will influence what the myco-toxindoes).•Digestivesystemincludingliver,mucousmem-branes–fumonisins,T-2toxin,patulinandDON;

What are mycotoxins?

fiGure 5 ergot on millet fiGure 6 Stenocarpella (diplodia) damage

on-farm mycotoxin control in food and feed grain8

•Respiratorysystem,lungs–trichothecenes, fumonisins;•Nervoussystem–fumonisins,trichothecenes, cyclopianzoicacidandergot;•Cutaneoussystem,skin–trichothecenes;•Urinarysystem,kidneys–fumonisins,ochra toxinA;•Reproductivesystem,T-2toxin,zearalenone;•Immunesystem–aflatoxinsandmanyothers;•Vascularsystemincludingbloodvessels,liver –aflatoxins,sterigmatocystin.

Symptomsoccurringinindividualanimalsandmanaredescribedinmoredetailbelow.

humansAflatoxins are at present the only mycotoxinsthat have caused human fatalities as a resultof acute poisoning. Known fatalities were firstrecordedinIndiain1974,whenunseasonalrainandfoodscarcityforcedpeopletoeatmaizethatwas heavily contaminated with this mycotoxin.Thereafter, contaminated maize consumptionhas resulted inhumandeaths inKenya in1982and,morerecently,in2004and2005whenmorethan200peopledied.

Aflatoxins, likemanyof theothermycotoxins,suppress the immune system in humans andso increase the susceptibility to infection byother microbes. Aflatoxins have similar effectsto those caused by HIV/AIDS and these toxinsmayevenmakepeoplemorereadilysusceptibletoHIV/AIDS.

AflatoxinB1isaverypotenthumancarcinogen,inparticularcausing livercancer.Liverdamageresults inabnormalbloodclotting,developmentof jaundice, haemorrhaging and a reduction intheimmuneresponse.

The trichothecene, T-2 was thought to beresponsible for causing Alimentary Toxic Aleu-kia (ATA) in Siberia during WWII. Thousandsof people were affected when they had to eatgrain which had been allowed to over-winter inthe fields. Symptoms included vomiting, acuteinflammation of the digestive system, anaemia,

circulatory failure and convulsions. ATA alsooccurredinKashmir,Indiain1987,wherepeopleate bread made from mouldy flour; symptomsincluded vomiting, diarrhoea, inflammed throatandbloodystools.T-2maybecarcinogenic.

In combination with T-2 and other trichothe-cenes, DON resulted in human illness (myco-toxicosis)inIndia.SimilaroutbreaksoccurredinJapanandChina,thelatterin1984/5frominges-tionofmouldymaizeandwheat,causingnausea,vomiting, abdominal pain, diarhhoea, dizzinessandheadache; theonsetofsymptomsoccurredwithin30minutes.HumanoesophagealcancerinTranskei,SouthAfricaandChinahasbeenasso-ciated with presence of F. verticillioides, whichproducesfumonisins.

cattleInitially,thereductioninperformanceasaresultofmycotoxiningestionmaynotberecognisable.Within days or weeks the effects of continuedmycotoxin consumption becomes more pro-nounced. Animals go off their feed, may sufferfromdiarrhoea,haemorrhaging,ketosis (excesssugar in the blood: diabetes) and from a dis-placed abomasum (4th stomach). Furthermore,reproductiveeffects,suchasswollenvulvasandnipples,vaginalandrectalprolapse,mayoccur.

Mycotoxinscanbedetoxifiedintherumenbutcattlemaystillsuffertheeffectsofthetoxins.Itisnotpossibletopredictjustwhattheeffectsarelikelytobesoitisalwaysbettertoavoidfeedingcattle mouldy feed if possible. Dairy cattle aremoresusceptiblethanbeefcattle.

All livestock is affected by aflatoxins. Matureanimalstendtobelesssusceptiblethanbreed-ing and growing stock but young, pre-ruminantanimalsarethemostatrisk.

Feedlevelsof60-100ppbaflatoxinsmayeffectperformance.Chronicsymptomscanoccurwithcontinuedintakeof700-1000ppbin200-kgcattleanddeathhasoccurredwithinfivedaysinfeed-ingtrialswhenthediethascontained10,000ppb.

9

Evenlower levelsofaflatoxinsmaycausetheseeffectswhenothermycotoxinsarealsopresent.

In dairy cattle, milk yield is reduced by afla-toxins and DON consumption, and both reducereproductive efficiency. Aflatoxin M1 (a metabo-liteofaflatoxinB1)canbesecretedintothemilkat 1-2% of dietary intake when feed levels are50 ppb or more. However, if contaminated feedis removed, milk residues disappear in 48-72hours.

Zearalenonemaygiverisetoabortionsindairycattle,aswellasreducingfeedintake,milkpro-duction and cause vaginitis, vaginal secretions,poor reproduction performance and mammaryglandenlargement in virginheifers. T-2causesfeed refusal, gastroenteritis and may lead todeath.

PoultryAflatoxins were responsible for the first majoracutemycotoxinoutbreak.IntheUnitedKingdomin the early 1960s, aflatoxins caused ‘Turkey X’disease, which was associated with the deathof thousands of turkeys, ducklings and other

domesticanimalsthathadeatenadietcontain-ingcontaminatedgroundnutmeal.

Less than 20 ppb aflatoxins in the diet willreduceresistancetodisease,decreaseabilitytowithstand stress and bruising, and make birdsunthriftyandtheirconditiongenerallypoor.Youngbirdsaremoresusceptiblethanlayinghens,andducksandturkeysareparticularlyatrisk.

Zearalenone causes impaired fertility, still-birthsand reducedspermquality. T-2toxinandothertrichothecenesmay:suppresstheimmunesystem; reduce feed intake and cause weightloss; cause skin irritation (feather loss) andmouthlesions,diarrhoea, internalhaemorrhag-ingandsevereoedemaofthebodycavity.Deathmaywellresult.

PigsNursing or nursery age swine are sensitive toaflatoxins. Feed levels of 100-400 ppb affectbreeding stock, unweaned and growing pigs(less than100kg).Aswithotheranimals, thereisusuallyareducedabilitytoconvertfeedlead-ing to a reduced rate of weight gain. Levels of400-800ppbhavecausedliverdamage,bleedingdisorders, suppression of the immune system,abortionanddeath.

What are mycotoxins?

box 1

Acute effects

• reduced feed intake

• reduced weight gain or weight loss

• reduced feed efficiency

• increased susceptibility to stress

• decreased reproductive performance

• severe haemorrhaging resulting in death

Chronic effects:

• unthriftiness

• anorexia

• prolapse of the rectum

• liver and kidney damage, resulting in

prolonged blood clotting time

• depression of the immune system

• oedema in the abdominal cavity and gall

bladder

SymPtomS of AflAtoxicoSiS in cAttle

box 2

• stunted growth as a result of poor food

conversion

• increased mortality

• reduced egg size

• reduced egg production

• liver and kidney disorders

• leg and bone problems

• suppression of the immune system with

increased susceptibility to bacterial

infections

• decreased blood clotting results in down

grading and rejection due to massive

bleeding and bruises

effectS of AflAtoxicoSiS in Poultry

on-farm mycotoxin control in food and feed grain10

would be most susceptible to problems withmycotoxin-contaminated grain. Lightly workedhorsesfedlessgrainaremorelikelytoeatmyco-toxin-contaminated hays or forages, such ascerealstover.Sincemouldyforagesarelesspal-atablethannormalforage,horsemaywellrefusefeed before ingesting sufficient to do severeintestinaldamage. Insteadtheymaysuffermildcolic.Mouldsaffectingfeedgraindonotusuallyaffectpalatabilityandsothosehorsesfedgrainarethosemostoftenexposedtomycotoxins.

Maximum aflatoxins levels for non-breeding,maturehorses(2-yrandabove)shouldbe50ppb.Growing, breeding and working horses shouldreceive aflatoxin-free diets. However, as theeffects on horses are not well understood allhorsesshouldbefeddietsfreeofmycotoxin.

Fumonisins, which seem to be particularlytoxictohorses,causeELEM(seeTable2),whichis characterised by lesions in the brain. Inci-dences of ELEM have been reported in USA,Argentina, Brazil, Egypt, South Africa, China; itmay well occur in other countries where insuf-ficientexpertisepreventsdiagnosis.

General effects of mycotoxinsAsummaryofthemorespecificeffectsofmyco-toxins is shown in Table 2. Aflatoxins are carci-nogenic, with the liver being especially suscep-tible. Trichothecenes, and T-2 in particular, areresponsible for causing haemorrhaging in farmanimals.FumonisinB1isacentralnervoustoxin,andalsoaffectsliver,pancreas,kidneyandlunginmanyanimals.

Aflatoxinsandochratoxinshavebeenfoundinmilk,meatandeggs.Thisisaparticularconcernforhumanhealthindevelopingcountrieswheremonitoringisnotaroutineorregularprocedure,and where animals are likely to consume highlevelsofthesetoxinsinfeed.

Penicillium species are also responsible forproducing two toxins,penitrem-Aandroquefor-tine C, that induce tremors. These symptomshave been mostly observed in dogs that have

Zearalenone has similar effects as it doesin poultry, causing swollen vulvas, and vaginalor rectal prolapse in pre-pubertal gilts. It alsocausestheuterustoenlargeandswellorbecometwisted,and theovaries toshrink. Inboars, thetestes atrophy and mammary glands enlarge.Generally,thereisadecreaseinfertility.DONcancauseseverevomitingandmayinducepigstorejectfeed.

Fumonisinscauseporcinepulmonaryoedema(PPE),anaccumulationoffluidinthelungs.OTAisassociatedwithkidneydamage.

Sheep and goatsThe effects of aflatoxin ingestion are similar tothose occurring in other ruminants. The liverand kidneys may be damaged, and the ani-malsbecomeanaemic.Earlysymptomsincludedepression,lossofappetite,weaknessandslowmovement.

Feedcontainingpatulincausenasaldischarg-es,andlossofappetiteandrumination,andbodyweight.

horsesAsnon-ruminantshorsesmaybemoresuscepti-bletomycotoxins,whichmayberesponsiblefor:

• colic• neurologicaldisorders• paralysis• hypersensitivity• organdeterioration• reducedrateofgrowth• poorfeedefficiency• impairedfertility• deathThecumulativeeffectsoffeedinglowlevelsof

mycotoxinsmayresultinagradualdeteriorationofbodyorganfunction.Thisaffectsgrowthrate,feedefficiency,fertility,respirationrate,theabil-itytoperformworkandlifespan.

Working horses have a high energy require-ment and require high concentrate intake, and

11

It is clear that mycotoxins can have seriousrepercussions for the livestock industry. Eventhoughourknowledgeof theeffectsofmanyofthetoxinsissketchyitisbesttoerronthesafesideandpreventanimalsfromingestingmouldygrainandfeed.

The following sections describe how we canavoidgrainbecomingcontaminatedwithmould.

beenallowedtoroamaroundtrashandcompost-ing mouldy food, especially dairy products. Lowquantitiesofthetoxinsmaycausetremorswhichlastforseveraldaysbutlargerdosesmaycauseseizuresandresultindeath.Otheranimalsthathavebeenaffectedby thesemycotoxins includecattle,sheep,rabbits,poultryandrodents.

What are mycotoxins?

TABLE 2 SymPTOmS OF myCOTOxINS IN ANImAlS CONSUmING CONTAmINATED FEED

mycotoxin fungi associated Symptom/toxicology

Fumonisin Fusariumverticillioides(moniliforme),F.proliferatum

Equineleukoencephalomalacia(ELEM),porcinepulmonaryoedema,liverandkidneydamageinotherdomesticanimals,(oesophagalcancerinhumans:noprovencausallink)

Deoxynivalenol(DONorvomitoxin)

F.graminearium Feedrefusal,reducedweightgain,diarrhoea,vomiting,reducedreproductiveperformance,increasedmortality,reducedeggormilkproduction,(nauseaandheadachesinhumans)

Zearalenone F.graminearium Oestrogenicsyndromes,mammaryandvulvarswelling,uterinehypertrophy,infertility,increasedbloodclottingtime,increasedmortality,reducedgrowth,increasedsusceptibilitytodisease

Trichothecenes F.graminearium,F.culmorum,F.poae,,F.solani,F.nivaleF.sporotrichioides,(T-2toxin)

Alimentarytoxicaleukia(ATA),digestivedisorders,reducedfeedefficiency,reducedgrowth,bloodydiarrhoea,reducedeggandmilkproductionnecrosis,haemorrhages,orallesionsinbroilerchickens,increasedbloodclottingtime,increasedmortality.

Ochratoxins Penicilliumverrucosum(temperateclimates),Aspergillusochraceus

Porcinenephropathy,renaltoxicity,immunosuppression,varioussymptomsinpoultry

Citrinin Penicilliumcitrinum.,Aspergillussp. Kidneydamage

Cyclopianzonicacid Penicilliumcyclopium,P.commune,P.camembertii,Aspergillusflavus,A.versicolor

Neurotoxin

Sterigmatocystin Aspergillusnidulans,A.versicolor Carcinogen,mutagen,affectsliver

Ergot Clavicepspurpurea Vertigo,staggers,convulsions,temporaryposteriorparalysis,anddeath.Decreasedbloodsupply.Reducedgrowth,tailloss,reducedreproductiveefficiencyinpigs.

Patulin Various Depressimmunesystem,carcinogen,neurotoxin,stomachirritant,nausea,vomiting,ulcers,haemorrhages

Aflatoxins Aspergillusflavus,A.parasiticus Livernecrosis,livertumours.Reducedgrowth,depressedimmuneresponse,carcinogen;