International Dairy Topics • Volume 16 Number 1 11

Up until the 1980s, the impact ofmycotoxins – secondarymetabolites including yeasts,

mushrooms and moulds that are producedby fungal species in feed under stressfulproduction conditions – was only studiedin monogastric animal species.

by Maxime Hilbert, Global Additive Category Manager,

Cargill Animal Nutrition.www.cargill.co.uk

The reason that there has been lessconcentration on the impact on cattle isthat research from the 1980s showed thatruminants were more tolerant to theadverse effects of acute (high dose andrapid) or chronic (slow development ofinfection) mycotoxicosis and that this wasdue to the ability of rumen microbiota todetoxify the mycotoxins.However, additional research has shown

that not all mycotoxins are metabolised tonon-toxic components, that some arehardly changed (aflatoxin, fumonisin) andalso that some rumen metabolites like thatof zearalenone are more toxic than theparent compound. Also, while adult cattleseem to be better equipped to deal withingested toxins than their monogastricequivalents, calves do not have a fullyfunctioning rumen and are at risk. Diets rich in ready fermentable

carbohydrates also reduce the number ofmicro-organisms in the rumen drastically,

disabling the mycotoxin deactivatingcapabilities even in adult cows. Also,mycotoxins that exert antimicrobialeffects – such as patulin – are of greatsignificance in ruminants as they impairruminal function. This results not only in malnutrition but

also facilitates absorption of othermycotoxins, which normally would nothave passed the rumen. Dairy cows also have to produce much

more milk per cow today than they didback in the 80s, which means that there is avery high dry matter intake (DMI) per cowper day and much more risk of mycotoxinpoisoning.

Other mycotoxin challenges

Although mycotoxins rarely occur inisolation and are generally more risky when

combined, it is useful to understand theirindividual impact on cattle productivity.The individual mycotoxins of greatest

concern to dairy cattle, and commonsymptoms, include:l Ergots produced in small grains, fescue,and other grass – produce nervousdisorders and tremors, and impact fertility.l Aflatoxin, which is generally produced byAspergillus mould, and which can causereduced feed intake, weight loss or lowergrowth rate and poor reproductiveperformance. Milk production can also dropdramatically. Chronic exposure to aflatoxinis characterised by unthriftiness, anorexia,drying and peeling of skin on the muzzle,liver damage, elevated levels of bloodconstituents and oedema in the abdominalcavity. Calves are more susceptible thanolder animals and almost any level ofaflatoxin-contamination in the ration maylead to some liver damage. Prolongedexposure at low levels can have a largeimpact.l Deoxynivalenol, zearalenone, T-2 toxin,and fumonisins, which are produced byfusarium mould and cause issues rangingfrom digestive, feed intake and milkproduction issues through to gastro-enteritis, intestinal haemorrhages, abortion,vaginitis, poor reproductive performance,endocrine and exocrine systemmalfunction, immune system suppressionand mammary gland enlargement. l Ochratoxin, PR toxin, mycophenolic acid,and roquefortine C produced by Penicilliummoulds. In the rumen of adult cows,protozoa degrade ochratoxin A rapidly into

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Winning the war againstmycotoxins – a challengefor dairy farmers

Table 1. Occurrence of type of mycotoxins per diet component.

Diet component Mycotoxins

Concentrates (cereal grains, corn gluten, soybean products, etc)

Aflatoxin, Fumonisin, Zearalenone, Trichothecenes (T2/HT2/DON), ergot alkaloids

Pasture grassesLolitrems, Paspalitrems, Penitrem, Ergovaline(Ergot alkaloids), Trichothecenes, Citrinin

Preserved feed (silages, hay, straw)

Aflatoxins, Patulin, DON, Zearalenone,Mycophenolic acid, Penicillic acid, Roquefortins, Marcfortine, Andrastin,Gliotoxin, Ergot alkaloids, Citrinin

Fig. 1. Effect of increasing DON concentration on milk production in dairy cows (300herd study of 50,000 cows, North Carolina State University).

2000

-200-400-600-800-1000

DON concentration (ppm)0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Milk reduction per

animal (m

l/day)

12 International Dairy Topics • Volume 16 Number 1

happen both before harvest (90%) becauseof extreme weather conditions (drought,excessive rain or heat) or after during grainstorage. The occurrence of mycotoxins shows a

geographical pattern and some countriesare more impacted than others (Fig. 2).Aspergillus species meet optimal

conditions in tropical or sub-tropicalregions, whereas fusarium and penicillinspecies are adapted to moderate climates(North America, Europe, Asia). However,worldwide trading of feed meansmycotoxin problems can be seen anywhere.The extreme weather conditions that

generally cause mycotoxins are much morecommon today than when they were firstdiscovered in the 1980s. Extreme precipitation, storms and floods

create moist conditions that encouragefungal growth, drought weakens the seedkernels of plants, allowing greater fungal

contamination and increased temperaturespromote fungal growth.

Winning the war before it begins

We can not eliminate mycotoxinsaltogether but the following factors willhelp you get some control over thesituation. For example, good landmanagement, particularly pre-harvest willlessen the risk. The amount of toxin produced depends

on physical factors (moisture, relativehumidity, temperature and mechanicaldamage), chemical factors (carbon dioxide,oxygen, composition of substrate, pesticideand fungicides) and biological factors (plantvariety, stress, insects, spore load). The most important factors influencing

mould growth are moisture (water activity),temperature, availability of nutrients and

Fig. 2. Prevalence of different mycotoxins per region in the world in 2015.

ochratoxin-α, which has little effect. Incalves, however, this causes polyuria,depression, lower growth, low specificgravity of urine and dehydration and it has anegative impact on the kidneys and immunesystem.

The extent of the problem

Recent statistics indicate that at least 25%of all crops are estimated to be affectedannually by mycotoxins, resulting infinancial losses of ~$5billion every year.Apart from the obvious loss of feed, there

is the cost of inspection and analysis beforeand after shipment of raw materials, costsof detoxification and productivity losses.When combined, the expense of dealingwith mycotoxins could be ‘staggering’whatever the species.Conserved forages and concentrates by

their very nature attract mould growth andmultiple mycotoxins. Even though cerealsand concentrates regularly contain multiplemycotoxins, it is estimated that over 80%of mycotoxins fed to cattle are from forageand straw. Grazing systems cannot be considered

completely safe as fresh grass can also becontaminated with mycotoxins. Research has shown that mycotoxins are

becoming more prevalent as more complexingredients/by-products are used in feedto control animal production costs.Products like Dried Distillers Grains and

Solubles (DDGS), a byproduct of ethanolproduction that is commonly used toreduce the cost of protein in the diet, haveamplified levels of mycotoxins that areformed in already infected corn duringfermentation process, especially in times ofdrought. Contamination with mycotoxins can

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International Dairy Topics • Volume 16 Number 1 13

oxygen. Pre-harvest conditions are critical.Another important factor is reducinginfection pressure in the field through croprotation, tillage and avoidance ofsusceptible varieties. For instance, growingcorn on corn can multiply by 5 to 10 theamount of deoxynivalenol compared withgrowing corn after peas or beets. Also, the type and use of fertiliser can

impact fungal contamination. Weeds cancontain a broad range of fusarium species,but killing the weed does not decrease thefusarium incidence because it will increasethe plant debris on the soil. Insects alsocarry fungal spores so cautious use ofpesticides can help. Changes in planting date or ripening of

the variety can also impact fungal infectionand mycotoxin contamination, but weatherchanges can undo this potential advantage.For wheat and barley, avoid plant varietiesthat mature late in the growing season. Earlier harvests result in lower

concentrations of mycotoxins. Also thetime of day of harvesting will influence thehumidity of the crops. Avoid mechanical damaging and where

possible remove visibly infected material tominimise fungal infection during storage.Because fusarium spores are present in thesoil, the cutting height of the harvestermachine will be an important factorreducing soil contamination. Ploughing and tillage will decrease DON

content in the following crop, burning ofthe crop residues will reduce the soilcontamination. To minimise mycotoxinissues in silage, it is important that the cropbeing preserved has the optimum moisturecontent for ensiling (650-700g/kg for pitsilage and 500-550g/kg for baled silage),that the crop is compacted/packed tightlyand the cover adequately restricts oxygenaccess/preserves anaerobic conditions.Baled silage must be handled carefully to

avoid damaging its cover and to keep pestsout. For clamped silage, the solo frontshould be removed during feed to avoidover-exposure of any one area.

Establishing problems and identifying the best solutions

l Testing feedTaking samples of feed to test for the sixmore common mycotoxins found in dairydiets, aflatoxin, deoxynivalenol (DON),zearalenone (ZON), ochratoxin, fumonisin,T2 without any prior knowledge of thepotential mycotoxin challenge is thegreatest source of error in quantifyingmycotoxin contamination. Mycotoxins mayoccur in feedstuff despite negativeanalytical results. Mycotoxins are also not homogenously

dispersed in feedstuff; they are oftenconcentrated in small areas in corners offeed stores, in the top layers of silageclamps, in very small packets of dry feed orin small areas of a field where crops are

diseased or stressed and so can easily bemissed. The only way to avoid this is toincrease sampling frequency. Theeffectiveness of a control plan greatly relieson the number of samples analysed. It istherefore important to get access to or togenerate a significant number of records tobe able to identify trends in raw materials.

l Use anti mycotoxin additives (AMA) as apreventative measureThe usual approach is that producers andfarmers introduce AMA as a preventativemeasure, sometimes administering it allyear round. For this strategy to make any difference,

you will need to use a technically relevantinclusion rate – not 0.5kg/mT as if youreally have mycotoxins in your feed, 0.5kgof any product will not solve the issue. Therelevant inclusion rate for preventive useshould be around 1.0-1.5kg/mT feed (whenproducts are enzyme, plant extract, yeast oraluminosilicate based).

l Taking control by accurately predictingthe extent of your issueThe only way to keep cost under control isto combine preventive use of AMA with adecent mycotoxin control plan based on anonline pattern database showing potentialrisks for harvests in different geographies.This way, if the mycotoxin load in rawmaterial increases, one has a chance toadapt AMA inclusion rate accordingly.We suggest the most cost effective way

to manage mycotoxin risk in youroperations would be to use a Lateral FlowDevice (LFD) to check your own materials.This data can then be added to the online

database and reports run that can help youdiscard contaminated raw materials beforethey enter your operations or allocate themto different species who are less sensitiveto the particular mycotoxins that arecontaminating the feed.

Conclusion

No ruminant feed is completely free frommycotoxins. Additionally, no feed can beexpected to contain only one mycotoxin.But rather than despairing, we shouldcelebrate the fact that in the past fewyears, scientific innovations have resulted inimprovements in mycotoxin detectionincluding high performance liquidchromatography (HPLC) and massspectrometry (MS). We can now detectlevels as low as 1ppb or even less.Taking account of mycotoxin

contamination patterns in feed materials viaa global online database can also be a greathelp in helping you achieve control in amore proactive, efficient and cost-effectiveway. n

References are availablefrom the author on request