On-farm mycotoxin control in food and feed grain ... · ON-FARM MYCOTOXIN CONTROL IN FOOD AND FEED GRAIN training manual GOOD PRACTICES FOR ANIMAL FEED AND LIVESTOCK 1 Mycotoxins

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.


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 978-92-5-105852-7

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:[email protected]

© 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)


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

7

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;


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


•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.


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


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.


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;

13

Prevent mould dAmAGe before hArveStIt isessential thatprecautionsaretakenduringthecultivationofthecroptopreventFusariuminparticular,andothermouldssuchasStenocar-pella and Claviceps from becoming establishedduringthegrowingperiod.

There are various factors that influence thepotentialforpre-harvestfungitodevelop,includ-ing the physiological and morphological stateof the plant and climatic conditions. A plantthatisnothealthyispronetoinfectionbytheseparasiticfungi.Inturn,thehealthoftheplantisdeterminedbyitswaterandnutrientstatusandwhetheritissubjecttootherstressmechanisms,suchasbeingattackedbypests.

Firstly, it isimportanttoensurethattheseedused for planting is free from disease. Buyingand planting certified seed is perhaps the bestguaranteethattheseedisdiseasefree.However,not many farmers are able to afford certifiedseed, and usually resort to farm-saved seed,produced from the previous year’s crop. Farm-savedseedwillbesafetoplantaslongasithasnotbeeninfectedwhilststoredatthehomestead.Itisvitalthatsuchseedisfreeofpestsanddis-easebeforeplanting,toensurehealthy,vigorousplants develop, i.e. those that are capable ofwithstanding attack during the growing season.Seed that is not free of infection will either notgerminate or will produce weak plants thathavea low thresholdof resistance topestsanddisease,andwhichwilleithersuccumbbeforeacropisproduced,orwillunderyield.

Drought stress, caused by a lack of water,is known to facilitate attack by mould. Lack ofwater allows the plant to crack, and so openspassage ways through which fungal spores canenter. This can happen to the stem or to thehead. Moulds can develop in the drying stems,

whichmightbeusedforanimalforageorhay,orinthegrain,whichwillgotofoodorfeed.There-fore,where irrigationsystemsfunction, farmersshouldalwaystrytosupplementlocalrainfalltoavoiddroughtstress.If it isnotpracticaltoirri-gate,plantandharvestasearlyaspossible.

Good husbandry practices will generally helpto fight against fungal invasion. It has becomepopular in recent years for farmers to practicezero or minimal tillage. This saves time andmoney,andwhere tractorsoroxenare inshortsupply or where labour is difficult to hire, cansave farmers and their families many days oftedious toil.However, thesebenefitshave tobetraded off against some negative effects. Forexample,withouttillage,cropresiduesremainonthesoilsurfaceandthesegraduallydeteriorate.These residues will harbour soil borne fungalspores, allowing them to over-winter, in timeto infect thenextcrop.Similarly,without tillagethesesporeswill remain in thesurface layerofthesoilinreadinesstogerminate.

Therefore,thebenefitsofminimaltillagehavetobeweighedupagainstthedrawbacks.Whatisclear, though, is that with any minimum tillageoperation, it is vital to keep the plot weed freeandtidywhilstthecropisgrowing,toensurethenew plants avoid any potential infection arisingfromoldvegetablematerialdeteriorating in thevicinity.

Practising good plant husbandry, includingweeding, will also help the plant fight againstinsect pests. Insect pests which damage thegrowing plant allow fungal spores openingsthrough which to invade plant tissues. Thusactiontoreduceinsectpestattackwillkeepfun-galproblemsaway.Thusinadditiontopractisinggood plant hygiene by keeping plots weed-freeand tidy, insects must be kept at bay by using

how to take care of food and feed


commercialinsecticideapplicationsorotherrec-ommendedmethodsofcontrol,suchasbotanicalpesticidesorbiologicalcontrol.

Actions must be taken to minimise the dam-agefromallpeststhatattackthegrowingcrop,not just insects.Rodents,suchascommonandNorwegian ratsand thehousemouse,mustbeexcluded. This is often difficult to achieve butevery effort must be made. Once again, goodplanthusbandry,keepingtheareacleanandfreeof plant matter, will reduce the risk of rodentdamage by limiting the number of harbourag-es. Removing vegetable matter in this way willreducetheamountoffoodavailabletotherodentanditmaylookelsewhereforafoodsource.

If possible, cropsshouldbe rotated fromoneseasontothenext.Cropsgrownonthesameplotin successive years have been shown to have amuchhigherlevelofmouldinfectionthanwhentheyarerotated.Rotationpreventsamouldthatiswellestablishedononetypeofplantfromhav-ingaccessinthefollowingseason,makingitlesslikely for infection to reoccur. This applies notonlytomouldsbuttootherpests,suchasinsectsandnematodes,aswell.

Plantstressmayoccurevenifthewateravail-ableisadequate.Ifthenutrientcontentofthesoilis lackingthenthegrowingplantwillalwaysbestressed.Thiswillbeseenwhenplantsbecomemisshapenandinternaltissuesmaybeexposedasthestembreaksopen.Lackofadequatesoilfertilitycanbeovercomebythejudiciousapplica-tion of organic or inorganic fertiliser. However,applying too much fertiliser will also put theplantunderstressandmakeitaprimecandidateforattackby insectsandmoulds. It is thereforeessential that fertiliserapplication is timelyandinthecorrectquantity.

Timing the production cycle is also key toobtaining a healthy crop at harvest. Plantingmust take place at the recommended time toavoidproblemscausedbythecropmaturingtooearlyormoreparticularly, too late,duringperi-odsofprolongedrainfall. Ifplantsmaturewhen

therelativehumidityishighorwhilstitisrainingthey will be prone to invasion by Fusarium, aswellasbeingsubject topre-harvestdamagebystorageinsectpests,whichthemselveswillhelpwith the diffusion and multiplication of mouldspores.

It is always advisable to plant seeds varietiesthatarepestresistant.Varietieswithresistanceto insectsandtoviralandbacterialdiseaseareavailable and should be used where the oppor-tunity arises. In Tanzania and Uganda in EastAfrica, for example, farmers are able to growmaize and sorghum varieties that are resistanttoMaizeStreakVirus,SorghumLeafBlight,GreyLeafSpotandStriga.Ofcourse,thisisnotalwayspossible because seeds of this type are notalwaysavailable tobuy,either locallyornation-ally. Furthermore, these varieties are usuallymore expensive to cultivate than non-resistantvarieties,andcertainlymoresothanlocallypro-ducedseed.Nevertheless,iffarmersdohavetheopportunityandthefinancialwherewithaltobuyanduseresistantvarietiestheyshoulddoso.

Cultivar differences exist for many pre-har-vest factors including pest resistance, droughttolerance, stalk strength and husk cover. Thereare significant differences in keeping qualitiesbetween different crop varieties. ‘Local’ variet-ies of maize, which have small cobs with tight,elongatedhusksthatcompletelyenclosetheker-

fiGure 7 tight husk of local maize variety

15

nels,arerelativelyresistanttoinsectattackandthereforelesssusceptibletofungi.Thesheathingleavesprovideaphysicalbarrier toentry.Com-posite and more particularly, hybrid varietiestendtohavemuchpoorerhuskcover,theleavesfailtofullyenclosethelargercobsofthesevari-eties.Consequently, theyaremuchmorepronetodamagebyinsectsandmouldsandextracaremustbetakenduringcropmaturationanddryingtoensurethatthesevarietiesarenotinvadedbypestsanddiseases(inpractice,withoutartificialdrying,thisisdifficulttoachievewhererainsareprolonged).Conversely, thetighthusksofsmalllocal varieties restrict water loss and slow dry-ing.

Theabsenceofaprotectivesheafmakessor-ghumsandmilletsmoresusceptiblethanmaize.However,thesecropsdovaryintheirsusceptibil-itydue to thesizeandchemicalconstituentsofthe grain. Larger, soft grain varieties are moresusceptible than those with small, hard grains,andthephenoliccontentofmaizeandsorghumisdirectlycorrelatedwithresistancetopestdam-age;redandbrownsorghumislesssusceptiblethan white. Sorghum heads that are open aremoreeasilydamagedbybirdsandsomoreproneto fungal invasion. Small grain millet is muchless damaged by insects than larger sorghumgrainsandbotharelesssusceptiblethanmaize.

Unfortunately, there are few cereal variet-ies thatare resistant to fungalattackandnonehave been developed that will resist Aspergil-lus.Varieties thatwill resistothermouldshavemostlybeendevelopedforuseincooler,temper-ate climates and will not be of practical use tomost tropical and sub-tropical farmers. Theseresistantvarietiesinclude,forexample,awheatvariety developed in the US that is resistant toFusarium Head Blight (not yet commerciallyavailable).

TherearenoClavicepspurpurea(ergot)resis-tant varieties but as sclerotia cannot surviveformore thanonewinter in thesoil, plantinganon-susceptible crop in infected fields for two

yearswillclearthemout.Theareassurroundinginfectedfieldsshouldalsobeclearedofsuscep-tible plants. In severe cases, deep ploughing toburysclerotiaisalsohelpful.

Prevent mould dAmAGe durinG hArveStThe two most important factors that influencemouldgrowthoncetheplantismaturearewateractivity and physical damage. When the maizecob,sorghumhead,cowpeapodandgroundnutpodhavebeguntodry inthefield it isessentialtodrythemdowntoasafemoisturecontentasquickly as possible, and to do so with as muchcareasispracticable.

Rapid drying requires that harvesting beundertakenassoonaspossible.However,delaystoharvestingmaybeunavoidableif,forexample,it is still raining; harvesting may then limit therateofdryingifthecrophastobekeptinaheapwhichrestrictsaeration.


• use certified seed or ensure seed is free of

fungal, bacterial or viral infection;

• avoid drought stress – irrigate if possible;

• sow seed as early as possible so that crop

matures early;

• if practising minimum or zero tillage

remove crop residues;

• weed regularly;

• control insect, mammal, bird and virus

pests;

• rotate crops;

• avoid nutrient stress – apply appropriate

amount of organic or inorganic fertiliser;

• plant resistant varieties where these are

available.

box 3 Action to tAke before hArveSt to reduce the riSk of mould contAminAtion And mycotoxin Production

on-farm mycotoxin control in food and feed grain1�

Thedecisiontoharvestmusttakeintoaccountseveralfactorsincluding:

• theprevailingclimate,• thelikelihoodofinsect,rodentandbirddam-

age,whichmightoccurthe longerthecropremainsinthefield;and

• the availability of drying facilities at thehomestead or local storage complex afterthecropistransferredfromthefield.

Where a farmer has access to drying facili-ties,forexampleatabuyingcentre,early,rapidharvestingandtransportingofgraintothedryerwithinadayortwowillbeideal.Bythismeans,thecropcanbedriedtoasafestoragemoisturecontentandsomouldattackandmycotoxinpro-ductioncanbeavoided.

Mostfarmerswillnothaveaccesstoartificialdrying facilities or will not be able to afford tousethem.Nevertheless,whatevertheircircum-stance, farmersmustenable thecrop todryasrapidlyaspossible.Therateofdryingwilldependonharvestingpractices,whichvarygreatly.Someproducerssimply leave thecropstanding in thefieldforseveralmonths,especiallyifweatherisdryandhot.Inthiscase,ambientairmovementsandtemperaturesaresufficienttocontinuallydrythecropdownwithouttheriskofmouldsdevel-oping. There is a risk, of course, if unexpectedrainfall occurs during this period, that mouldscandevelop.

Therateofdrying inthefielddependsonthecropitself-maizekernelsenclosedinsheathingleaves will dry more slowly than open sorghumheads–andonhowitistreated.Inmanycoun-tries, it is common practice to bend the headsover on the standing plant as early as possibletospeeddrying.Farmersalsocutcerealsatthebase of the stalk and pile the stalks with cobsorheadsintoconicalbundles,knownasstooks.This allows the field to be ploughed whilst thesoil isstillmoistandsoftbutthetightlyformedstooks may inhibit ventilation and slow drying.Somefarmers laybundlesofstalkson thesoil,andthisisdangerousasitcreatesanopportunity

forfungalsporesinthesoilto invadethegrain.This happens with legume crops in particular,and has been a major cause of groundnutsbecominginfectedwithAspergillus.Thisproblemcanbeavoidedbyplacingabarrierbetweenthecropandthesoil,forexamplealayerofmilletorsorghumstalks.Betterstill,placethecroponaplatformraisedabovetheground.

Caremustbetakennotonlytodrythecerealorpulsecropeffectivelybutalsothesameprac-ticesmustbeusedfordryingstover,strawsandhaulmsthataretobeusedasanimalfeed.Cropresiduesleftlyinginthefieldwilldryslowlyandarelikelytobeinfectedwithmouldspores.Theyshouldbeplacedonplatformssothatthereisnochanceofcontactwiththesoil,ortiedtogetherinuprightheapsorstooks.

Still, it isbetter for the farmer to remove thecropfromthefieldasquicklyaspossibleandtodryitatthehomestead.

fiGure 8 maize stook

17

Harvesting must be rapid but care must betakentoavoiddamagingthecrop.Ifthecrophasbeen dried in the field then careless handlingwillnotonlyresultingrainshatteringandweightloss,butwillalsocausegraindamageandallowinsectandfungalpeststoinvade.Whenharvest-ing with a tractor it is essential to ensure thattheequipment issetupcorrectly toavoidgrainbreakage due to mechanical damage; this isespecially important when using a tractor tothreshthecrop.

CaremustalsobetakentoensurethatsilageismadeundergoodanaerobicconditionswithalowpH, toensure that it remains freeofmouldandissafetofeedtolivestock.

Prevent mould dAmAGe After hArveSt dryingAlthough drying begins before harvest it mustbecontinueduntilthecropisputintostoreand,eventhen,furtherdryingmaystillbenecessary.Cerealsharvestedonthestalkorpulsesinpodscan be transported to the home and placed onplatformsor framestocontinuethedryingpro-

cess. Platforms must be raised so the floor isat least 0.7 m above the ground, the legs fittedwithmetalguardstopreventrodentaccess,andtreatedifnecessary,topreventtermiteattack.

The platform may be converted into a dryingand storage crib having walls made from wirenetting, bamboo, sisal poles, sawn timber orsimilar materials, which allow free movementofairacrossand through thecrop.Maizecobs,sorghum or millet heads and legumes in shellshouldbelessthan0.5mindepthinthedryingcrib so that air movement is not impeded anddrying restricted. The structure itself should be


fiGure 9 A drying platform (a), drying frame (b) and drying crib (c)

(a)

(b)

(c)

box 4

• harvest as quickly as possible

• avoid field drying

• transport the crop to the homestead as

soon as possible

• if lack of labour or time prevents removal

from field then dry on platforms raised

above ground (if climate is hot and dry crop

can be left to stand in field or cut and tied

into stooks) to dry

• bundles of stover should also be placed on

platforms to dry and not left to lie on the

soil

Action to tAke durinG hArveSt to reduce the riSk of mould contAminAtion And mycotoxin Production


nomorethan1.5mwide,anderectedsothatthelongsidestraversetheprevailingwindtoallowagoodflowofair.

Farmers often build these platforms above acooking fire. This has the advantage of speed-ing the drying process and may also help topreventpestdamagewhilstthecropisrelativelyexposed.

Drying crops spread thinly over the floor,whetheroncompactedsoiloraconcreteplinth,isacceptableifitiscleanandwellswept.Betterstill,asheetofpolytheneora tarpaulin-prefer-ably black in colour to better absorb the sun’sheat-oralayerofemptysacks,shouldbeplacedon the floor on which the grain can be spread.Thiswillallowthecroptobequicklymovedundercoverwhenrainisimminent.Caremustbetakentopreventthegrainfrombeingexposedtodust

andothercontaminantsintheair,andtoinsects,rodentsandbrowsinglivestock.

Relying on ambient climatic conditions whenthe crop is spread out on the floor, tied to aframe, placed on a platform or in a crib maynot dry the crop fast enough to prevent moulddamagefromoccurring;suchdryingmaytakeamonthormore inhigh relativehumidities.Onlytheuseofapurposebuiltdryerwillachievetherate of drying required. The simplest are solardryers,whichcollectthesun’sheatinsideaspe-ciallydesignedchamberthathasadequateventi-lationforremovalofmoistair.Themostbasicofthesearenaturalconvectiondryersinwhichtheairflow is induced by thermal gradients. Thesecanbe relatively cheapandsimple to constructand are appropriate for use by individuals orsmallgroupsoffarmers.

Asecondtypeofsolardryerisoneinwhichafanisusedtoforceairthroughasolarcollectorandthegrain.Thistypecanhandlelargerquanti-tiesofgrain,whichcanbeloadedontotraysandplacedinlayerswithinthedryer.

Somecommercialfarmersandfarmergroupsmayhaveaccesstolarger-scaledryersoperatedby marketing boards, grain buying companiesand millers and feed compounders. The oppor-tunity to use such facilities should be taken,especially inareaswhere theprevailing relativehumidityremainshighthroughmuchoftheyear,for example, in much of West Africa and SouthEastAsia.

threshing, shelling and winnowingCarefulhandlingofthecroponceithasdriedcancontributesignificantlytotheavoidanceofmoulddamageoncethegrainisputintostore.

Inmaypartsoftheworldfarmersandtheirfam-iliesthreshorshellcerealsandgrainlegumesbybeatingthecrop,eitherlooseorplacedinsideasack,withastick.Thismethodisquickandsim-ple but does cause heavy damage to the grain,especiallyoflargerkernelsofmaize,beansandgroundnut. It is also common for small grain

fiGure 10 A solar dryer being used for drying chilli peppers

19

milletstobethreshedinamortarandpestle,amethodthatproducesalargeproportionofbro-kens.Storingbrokengrainsmayresult inheavymouldinfectionandmycotoxinproductionespe-ciallyinperiodsofwetweatherorhighhumidity;wheretherelativehumidityremainslowforlongperiods,suchasinCentralandSouthernAfrica,mouldattackmaynotoccur.Furthermore,wheregrainsareconsumedquicklyafterthreshingthepresenceofbrokenswillnotmatter.

Farmersoftenusetheirhandstoshellmaize,breakinggrainsfromthecobbetweenthumbandforefinger.Althoughthismethodcanbelaborious

correctlycalibratedorsetup,acommonoccur-rencewhen farmersarenot thoroughlyconver-santwithamachinetheymayonlyhaveonhire.

StorageUnthreshed produceOnce grain has been dried sufficiently it maybe threshed before storage or left unthreshed.Smallquantitiesofcerealsontheheadorgrainlegumesinpodsmaybestoredloosewithinthehouseorstore,onthefloor,incontainerssuchasusedoildrums,inwovencribsorbaskets,orontopoforbeneaththeroof.


fiGure 11 various hand-held, bicycle operated and mechanical shellers

- it is usually a social occasion allowing familyand friends to meet and talk – damage to thekernels is usually low and the quality remainsgood.Maizecanalsobeshelledusingavarietyofhand-held gadgets or pedal-operated mechani-cal devices. All of these tend to produce goodqualitygrainbutarerelativelyscarceinfarmingcommunities.Toworkeffectively,allthesemeth-ods require the grain to be sufficiently dry forsafestorage;ifgrainiswetthreshingisdifficulttoundertake.

Commercial farmers may use tractor-drivenshellersandthreshers.Eventhesecanresultinsubstantialquantitiesofbrokens if theyarenot

It is bad practice to place food commoditiesdirectlyontoanearthenfloorasthereisnothingtopreventmoistureinthesoilmigratingintothegrains. This will lead to mould and mycotoxincontamination. The same will apply even if thefloorisconcreteasit isstillporous.However,ifawaterbarrier,suchasapolythenesheet,hasbeenlaidaboveorinsertedintotheconcretethenthecropwillremaindry.

Unthreshed commodities remain exposed toinsect and rodent pests unless protective mea-sures are introduced. For insects, this requiresthe application of either a conventional insecti-cide,suchasActellic2%dust,ormoretraditional


protectants such as those derived from plants,e.g. ‘neemkernelpowder’.Commoditiescanbestoredintheloftorroofspaceoronaplatformabovea fire. The firewill notonlydry thegrainbuttheheatandsmokemaykillinsectsordrivethemoutofthegrain.However,thisisnotalwayseffective,assomeinsects,suchasProstephanustruncatus, the larger grain borer, can toleratetheseconditions.

Againstrodents,farmersstoringcropsintheirhouse may, by themselves, provide sufficientdisturbance to keep rodents at bay. Storageelsewhere may need more specific protectivemeasures,suchasbafflesonthesupportpolesof cribs, laying break-back traps, keeping theareas around stores clean and free of debris,and perhaps acquiring a cat. Rodent control isdifficult to achieve because of the ability of theanimals to avoid unfamiliar situations. The useofsyntheticrodenticidesonsmall-scalefarmsisnotappropriatebecauseoftheinherenttoxicityofmostoftheproductsmarketed;theirusewouldputatriskyoungfamilymembers,domesticani-malsandbrowsinglivestock.

Threshed produceIncreasingly, farmers are storing cereals andpulsesasloosegrain.Graincanbestoredintra-ditional or improved woven structures, in metaltanks or drums, in plastic containers or sacks.

Plasticandmetalcontainerssoldforwaterstor-agemake idealgrainstoresbut thegrainmustbeverydry topreventmouldgrowthandmyco-toxinproduction.

Farmstoragestructuresmayberelativelysim-plecylindrical,tightlywovenbasketsthatmayormaynotbeplasteredwithmudand/orcowdung;cylindrical or oblong mud brick stores; burntbrick structures with or without compartments,orornatehouse-likestructures.Thereisawiderangeofstoragedesignsandavarietyofdifferentmaterialsfromwhichtheyarefabricated,includ-ing sisal poles, tree bark, bamboo, twigs fromvarious treesandgrass twisted intorope;sawntimber; grass thatch and corrugated iron areusedinroofconstruction.Designsvaryinshape,diameter,height,longevity,cost,andintheskillrequiredforconstruction.

Suchstoragestructuresmusthave:• A roof with a overhang, which is sufficient

totakerainwaterawayfromthegrain,andprovideshadetoreducediurnaltemperaturefluctuations that might otherwise result innight time condensation and wetting of thecontents. Grass thatch provides excellentinsulation but requires regular repair andneeds to be renewed every few years. Cor-rugatedironsheetsaremuchmoredurableandanytemperaturefluctuationtheycreateinsidethestorecanbeminimisedbypaint-ingwhitetheexternalsurfacesofthesheets.Cementtilesarebothdurableandpoorheatconductorssomeetbothneedsbut tendtobeexpensive.

• A support structure that raises the con-tainerabovethegroundtopreventmoistureentryfromthesoil. Ifthesupportsarelongenough,atleast1m,thenrodentbafflescanbe fitted. Supports are best made of burntbrick but mud bricks or wooden poles willdo,as longasprecautionsagainstpossibletermitedamageareput intoplace.Woodenpoles can be protected against termites byusing commercial insecticide such as ben-

fiGure 12 rodent in a break-back trap

21how to take care of food and feed

fiGure 13 farm storage structures

diocarborbysoakingordippingthepoleinusedengineoil.

• Amethodofaccessingthecommodityinthestore; this is usually achieved by having anopeningordoorinthestructureorbyraisingtheroof.

The quality and type of materials used inconstruction will determine the stores longev-ity.Raising thestoreabove thegroundwillalsoenable the area around it to be cleaned andinspected for signs of termites, storage insectsand rodent activity. Stores made from wovenmaterials can facilitate aeration as long as theweave is not too tight. During periods of rain,stores can be plastered with mud to restrictwaterentry; themudplasteralsohelps topre-venttheftbyanimalsandhumans.

In some counties, farmers store grain inundergroundpits.Theseprovideexcellentsecu-rity against theft. However, because they are

impervious to ambient conditions and are notabletobeaerated,grainplacedinsuchpitsmustbeverydryinordertopreventmoulddeveloping.Evenso,someairusuallydoespenetratearoundthe door of the pit, and it is not uncommon forcondensation to occur on the surface layers ofthegrain,whichdothengomouldy.It isimpor-tantforfarmerstobeawarethatgrainnearthesurface of pits may well be contaminated withmycotoxin even if there is no obvious sign ofmoulddecay.

Increasingly, producers are storing grain insacks.Thesemaybewovenpolypropylene(WPP),sisalorjute.Sacksmaybestoredindryingcribsorotherpurposebuilt storesbutare frequentlykept inside the house to improve security. Toavoid moisture migration into the grain, sacksshould never be stacked directly onto the floor.They can be stood on polythene sheeting, orraisedoffthegroundonpoles.Itisalsoadvisable


toensurethatagapremainsbetweenthesacksandthewallssothattheycanbeeasilyinspectedand remedial actions taken if rodent or insectdamageoccurs.

Grain that is tobestored forseveralmonths,whether in a storage structure or in sacks,should be treated with insecticide to protect itagainst insects, which are the most commonformofstoragepests.Thisisbestdonebymix-ingthegrainwithadiluteinsecticidedust,suchas Actellic 2%, before the sacks or stores arefilled.Insecticideisaddedandmixedinthesamewayassandandcementaremixedtomakecon-crete,amaximumof50kgbeingtreatedatonetime. Dilute dust insecticides are cheap to buyand have the advantage of requiring no specialequipmentforapplication;ashovel isall that isneeded.

in store Grain can remain in store for a matter of days,monthsorforayearormore.Whilstinthestoregrain should be inspected regularly to ensureit remains ingoodconditionand free frompestdamage. Inspections should coincide with grain

removals for food preparation, or when it isneeded to brew beer, feed animals or removedfor sale. Inspections should take place at leastonceaweek.

Thestoragestructuremustalsobeinspectedto ensure that it is in sound condition and hasnot sustained damage from browsing livestockandtermites.Sacksmustbeinspectedforholesmade by rodents though which grain may betaken or spilt. The presence of rodents is oftendenoted by the presence of droppings on sacksurfaces. The areas around the structures orstacksmustbekeptclean,sweptandfreeofrub-bishandotherextraneousmaterialtoeliminatebreedingsites.Sacksmustbeopenedandgrainexamined for signs of mould growth and insectdamage. Similarly, the contents of other struc-turesmustbeobservedwithequaldiligence.

Storing flour and compounded feedThe fine particles of flour are very attractive towaterparticlesintheair.Dryflourstoredforevenveryshortperiodswillquicklybecomemoist,theratebeingdependentontheambientconditionsinwhichthesackisstored.Moistflourwillallowfungal spores to germinate and very quickly adense mycelium will become visible. Thus it isessential that flour isonly stored for very shortperiods. However, small quantities can be keptsafelyinairtightplasticcontainersaslongasthe

fiGure 14 entrance to underground storage pit

fiGure 15 Sacks of grain stored in the house raised off the floor on poles.

23

flour fills thecontainer,expellingtheair inside;iftheflouronlypartiallyfillsthecontainerthenitcouldgomouldy.

Feed pellets similarly attract moisture soshouldonlybestoredforrelativelyshortperiods.Pelletsareactuallyformedwhenwaterisaddedtothemandthisadditionalwaterisremovedasthepelletscooldownattheendoftheprocess.If cooling is not fast the moisture present canpermitmoulddevelopment.

Flakedfeedandothercomponentsthathavealargesurfaceareatoweightratio,suchaswheatfeed, bone meal and fish meal can all readilybecomemouldyifstoredfortoolong,particularlyinrelativelyhumidconditions.Livestockkeepersshouldonlybuysufficientfeedtolastamaximumof 10 days; in some really hot humid countrieseventhisperiodwillbetoolong.

Silage and hayStorage containers should be airtight. Mouldproblemsonlyoccur ifsilage isexposedtooxy-geninair.Thiscouldhappenattheperipheryofthestoragesystem,forexampleattheedgesofplasticsheetsusedtocoverthesilage,especiallyif these are damaged in any way. Repairs mustbe made as quickly as possible and then thedevelopmentofmouldinaerobicconditionscanbestopped.

More importantly, fungal spoilage can occurwhensilageisbeingfedouttolivestock,asitisthenconstantlyexposedtotheair.Somespoilageatthistimeis,therefore, inevitable.However,tominimisethisproblemsilagecontainers,pitsandheapsshouldbekeptrelativelysmallsothattheycan be completely emptied in a relatively shorttime,1-2days.Thus it isbetter tohaveseveralsmallsilagecontainers,whichcanbeopenedinsequence, rather than one large one that mayresultinsignificantspoilage.

The fungus Penicillium roqueforti has beenidentified as being the predominant fungus indifferent types of silage. This and other silagemoulds,whichincludetheAspergillusandFusar-


fiGure 16 mixing insecticide dust with grain for storage


ium genera can be inhibited by additives thatpreventaerobicconditionsfromoccurring.Suchadditives include proprionic, benzoic and sorbicacids, and whilst commonly used in the devel-opedworld,aregenerallyprohibitivelyexpensiveforusebysmall-scalefarmersinthetropics.

Proprionicacidcansimilarlybeusedtoinhibitmould growth in bales of hay whilst they aresweatingandcuringdownbyevaporationtosafemoisture levels.Proprionicacid is sprayedontothe hay as it enters the baler and is commonlyused in the developed world. Where hay is notbaled but simply left as loose forage, mould

developmentisrestrictedbysimplyallowingthehaytodryquickly.

diSPoSAl of mycotoxin contAminAted GrAinDespite all precautions, it may happen thatstored grain will become damaged by mould.It must then be assumed that the grain is alsocontaminatedwithmycotoxins.

If the farmer has plenty of grain in store,he can afford to lose a small quantity that hasturnedmouldy. Ideally, thefarmermustdiscard

box 5 Action to tAke After hArveSt to reduce the riSk of mould contAminAtion And mycotoxin Production

drying

• Crop should be spread on a (black)

polythene sheet, tarpaulin or empty sacks

laid on the ground or on a concrete plinth.

• Unthreshed crop can be laid on platform

or in ventilated crib to dry; cobs can also

be tied in pairs and suspended from a

vertical frame to dry.

• In wet or humid conditions crop should be

artificially dried in a solar dryer.

threshing, shelling , winnowing

• handle crop carefully to avoid broken or

damaged grain.

• Use hand or pedal operated threshers if

possible.

• Avoid beating the crop with sticks as this

creates lots of damage leading to mould

development unless the grain is to be used

quickly and not stored.

Storage

• Store unthreshed produce or grain in a

suitable container which is raised above

ground level. If the crop has to be stored

on the ground ensure a suitable waterproof

barrier is in place.

• Treat a crop that is to be stored for more

than two months with a suitable grain

protectant to prevent insect damage.

• Protect the crop against damage by

rodents.

• External storage structures must have a

good roof with suitable overhang to provide

shade and to take away rain. They should

be protected against rodents and termites.

Access to the crop inside should be easily

achieved by having an opening or door in

the wall or a roof that can be raised.

• Sacks must be stored on a platform raised

above the floor.

• Produce must be inspected regularly to

ensure that it is free of mould, insect

and rodent damage; if damage is present

remedial treatment must be put into

place.

• Flour and feed must only be stored for

short periods to avoid mould development.

Small quantities can be kept longer in

airtight containers.

25

mouldygrainandanythatissuspectedofbeingcontaminated with mycotoxins; this will includeapparently clean grain that is in the vicinity ofthemouldyproduce.Thisgrainshouldbeburntorburied.

Most farmers in the developing world, how-ever, do not have a surplus they can afford towaste.Itmaywellbeabsolutelynecessaryforthemouldy grain to be used, especially in times ofseverfoodshortage.Whenthishappens,mouldyandsuspectgrainmustbedilutedwithaquantityof clean grain before it is used, the greater thedilution the better. Then this grain can be sold,usedforbrewing,orfedtoanimals.

Ifusedas livestock feed itshouldbe first fedto ruminants; ruminant microbes can detoxifysome mycotoxins. Beef cattle should be fedbefore dairy cattle, and cattle fed before sheepand goats. Mature ruminants should be giventhegrainbeforegrowingandpregnantanimals,andyoungstockshouldnotbefedthisgrainifatall possible. Similarly, young chicks should notbe fed contaminated grain or feed and maturebirds should be fed before growing poultry. Nosuspected contaminated grain should be fed toducks or turkeys as these are particularly sus-ceptible.


27

references

The following web sites were used for derivinginformationingeneral.http://www.dairylandlabs.com/pages/interpreta-

tions/molds_toxins.php:http://www.omafra.gov.on.ca/english/livestock/

dairy/herd/food/mico2.htm Tarr B (1996)Mould and mycotoxins- effects of moldy feedandmycotoxinsoncattle.

http://www.afma.co.za/AFMA_Template/code_of_mycotoxins.htm: Code of practice for thecontrolofmycotoxinsintheproductionofani-malfeedforlivestock,August2001/June2003

http://wilikipedia.org/wiki/Mycotoxinhttp://plantpathology.tamu.edu/aflatoxins/

effects.htm:http://www.thepoultrysite.com/FeaturedArticle/FATopic.asp?AREA=Nutrition&Display=298http://www.ces.ncsu.edu/depts/pp/notes/

Corn/corn001.htm: Mycotoxins in Corn, 4ppSKoenningandGPayne:

http://www.extension.umn.edu/distribution/live-stocksystems/M1179.html:Whitney,M

http://www.fao.org/docrep/U3350t/U3350t0e.htm:MycotoxinsandthefoodsupplybyBhatRV&MillerJD)

Tremorgenic mycotoxin intoxication by MaryMSchell, April 2000, Veterinary Medicinehttp://www.vetmedpub.com.

http://www.ces.ncsu.edu/disater/drought/dro-29.html:FonesFTetal.,

Effectsofmycotoxinsonthehealthandproduc-tivityofspecificproductionanimals (1994) In:Understandingandcopingwith theeffectsof

mycotoxinsinlivestockfeedandforage.NorthCarolinaCo-operativeExtensionService,pub-licationAG-523,Dec.1994.

(http://www.wisc.edu/fri/fusarium.htm: M EllinDoyleFusariummycotoxins1997.

http://193.132.193.215/eman2/english.asp:EuropeanMycotoxinAwarenessNetwork

YiannikourisA&JouanyJ-P(2002)Mycotoxinsinfeedsandtheirfateinanimals:areview.Anim.Res.51,81-99.

Fandohan, P., Hell, K., Marasas, W.F.O. andWingfield, M.J. (2003) Infection of maize byFusarium species and contamination withfumonisins in Africa. Afri9can Journal ofBiotechnology2,570-579.

http://www.mold-help.org/content/view/457/:Lillard-Roberts,S(2004)Mycotoxinlist.

Smith, J.E.; Moss, M.O. 1985. MycotoxinsFormation, Analysis, and Significance JohnWileyandSons.NY.

w w w . a r s . u s d a . g o v / R e s e a r c h / d o c s .htm?docid=8909 Sorghum head mould (fig-ure1c)

www.ent.iastate.edu/imagegal/plantpath/com/fusarium/1355.42fusariumearrot.html

http://maizeandgenetics.tamu.edu/aflatoxin.htm(Aspergillusrotinmaize(fig4)

http://sacs.cpes.peachnet.edu/fat/Ergot.jpgPhotoofergot

YiannikourisA&JouanyJ-P(2002)Mycotoxinsinfeedsandtheirfateinanimals:areview.Anim.Res.51,81-99.



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.

Documents

On-farm mycotoxin control in food and feed grain ... · ON-FARM MYCOTOXIN CONTROL IN FOOD AND FEED GRAIN training manual GOOD PRACTICES FOR ANIMAL FEED AND LIVESTOCK 1 Mycotoxins