Can we keep up with mycotoxins? The experts decide

[Guest guest]

Good article about how mycotoxins are becoming more prevalent in animal

feed, maise, etc. as a result of global warming.

Can we keep up with mycotoxins? The experts decide

PUBLICATION DATE: 02/13/2009

COMPANY: _Biomin_

(http://www.engormix.com/e_companies_showcase.asp?empr=496)

SOURCE: Biomin GmbH press release

Mycotoxins are always a major topic of discussion at the World Nutrition

Forum: hosts BIOMIN have been fighting them for 25 years and the battle is not

yet won - it just gets more complex. The Panel Discussion in 2008 focused on

sources of mycotoxins in animal feed.

Between them, the experts who took part in the panel discussion have made

around 2000 scientific presentations, ranging from posters to books. Chairing

the discussion, Professor Wayne Bryden of the University of Queensland,

Australia, brought the issue into sharp focus. 'In the developed world,' he

began,

'mycotoxins add to the cost of feed. In the developing world, it's a problem

of human health. But in both cases, it's the second biggest problem that has

been identified in animal feed.'

Fighting the unknown

Dr. Isabelle Oswald studies mycotoxins at INRA's pharmacology and toxicology

laboratory in Toulouse, France. She explained the increasing significance of

this group of toxins as a result of global warming and an increased reliance

on less traditional feedstuffs. In Europe, she said, 'we are very concerned

about Fusarium toxins: trichothecenes, fumonisin and zearalenone. But

ochratoxins and aflatoxins are becoming a bigger problem with global warming.'

To

tackle the problems, 'we need to understand how the separate toxins interact

together,' Oswald said. Fusarin C toxin, enniatins, beauvericin and

moniliformin

are relative newcomers to European agriculture, so important questions have

to be addressed now, including 'how do you measure their deleterious effect?

Are there effects before productivity is affected?' Some of the effects of

these toxins, said Oswald, 'are only seen post-mortem' in the liver, kidney and

other organs. Furthermore, 'immuno-modulation is a major problem with

mycotoxins', but to study the effects of any mycotoxins on an animal's immune

system: 'it's very important to stimulate it with an infection or vaccination

to

see the effects'.

Investing in testing

A multidisciplinary approach is clearly needed in the fight against these

damaging and sometimes elusive toxins. Dr. , a consultant with many

years' experience in sampling, identification and combating mycotoxins at

Romer Labs, explained how a deeper understanding was developed of how and why

many mycotoxins are produced in the field and under storage conditions means

that now, 'Farmers are aware of the problem of mycotoxins in crops. They

understand the importance of mycotoxins in the supply chain.'

Aflatoxin causes most concern, he said, 'because of their toxic nature and

the fact that they are highly carcinogenic,' but DON probably occurs most often

in US commodities. Fumonisins are a major problem for the pet food industry,

he continued, in horse feeds and sometimes in pig feeds; while ruminants and

chickens are relatively resistant. Environmental and geographical conditions

also play their part; and different mycotoxins and their combinations can be

expected more in some feedstuffs than others - for example mycotoxins can be

concentrated in distiller's dried grains and solubles (DDGS); and maize is

especially vulnerable to contamination with all major mycotoxins. This

information is very useful: demonstrated some matrices that have been

drawn

up for guidance. Forage and silage contamination, he said, are often

overlooked. Here, a 'whole variety' of organisms can be responsible for 'even

more

mycotoxins,' causing such common problems as 'fescue foot' or 'summer slump'.

So, 'although testing adds to the cost - this cost is lost in comparison to

the costs of not paying attention to good testing.'

Effective sampling systems needn't cost the earth, said Professor

Mallmann. In his position at the Federal University of Santa in Brazil,

Mallmann has been instrumental in developing effective systems to reduce

contamination and preventing it impacting on the country's livestock production

industries. Environmental conditions in Brazil can cause problems as they do in

the US: 'zearalenone increases after two years' drought,' he explained and

mycotoxin contamination in South America, he warned, can have serious

consequences, for the country's financial and human health. 'Recently,' he said,

'DON

and fumonisins are the most commonly found in silage, but each ppb results in

a 5 gram loss in the production of milk.' Furthermore, maize meal, an

important food ingredient across South America 'is an important source of

contamination.' So sample collection as Mallmann describes, really does deserve

'special attention.'

Beware masked mycotoxins

Professor Rudolf Krska took the debate into the future. New technologies have

rapidly found home in the study of mycotoxicology and Krska, based at the

University of Natural Resources and Applied Life Sciences (IFA-Tulln) in

Austria, discussed their application. 'We are moving gradually from single to

multitoxin analysis' he began, 'and are increasingly able to link mycotoxin or

metabolites to resistance genes in maize.' However, our analytical abilities

raise a number of important questions. For example, Krska asked, 'have we got

sufficient knowledge of the range of mycotoxins that are occurring? How many

toxins shall we determine? Do we know enough about synergy? And what's the

potential threat of undetected toxins?' Krska also raised the issue of 'masked'

mycotoxins. Modern analysis has revealed that deoxynivalenol (DON) can be

subject to conjugation reactions by plants to DON-3-glucoside. Although the

plant does this as a means of detoxification, to protect itself, once it has

been

ingested, the animal's own digestive enzymes can deconjugate the glucoside

and the toxin is released again. Worryingly, said Krska, masked mycotoxins 'are

present in large quantities in maize', quoting data from Berthiller and

colleagues (2005) where, in wheat samples, '45% of toxins were masked'.

Avoid expensive mistakes

Putting sampling strategies and analytical methods into practice can be

expensive, but, as Professor Gonzalo , of the National University of

Colombia, explained, doing without can be far more expensive in the long run.

Citing

well publicised mycotoxin-related instances in petfood over recent years,

pointed out that these cases may not have led to widespread fatalities if

the contaminated ingredients had not found their way into pet food. He then

showed the benefits of an effective sampling plan. If appropriate analytical

methods (incorporating sampling and sub-sampling) and limits of acceptance (to

apply an 'accept v. reject' decision system) are in place, explained , you

can prevent contamination in ingredients from reaching the finished feed.

Sampling and analysis can also be optimised by a better understanding of high

risk ingredients. 'Maize can support a number of toxins,' said .

'Fumonisins are almost never found anywhere to any extent except in corn

[maize].'

However, because 'fusarium grows inside the grain,' soybean is much less likely

to be contaminated. Wheat, barley and oats can be contaminated with most

fusarium toxins, including type A and B trichothecenes (wheat, barley) and

zearalenone (wheat). Knowing the type(s) of toxin(s) to expect in an ingredient

gives the analytical plan a head-start. Then, continued, 'you should also

take into account the level of inclusion of the ingredient and also, that not

all animals respond in the same way.' Pigs, as previous panellists had

discussed, are susceptible to all mycotoxins. 'Most mycotoxins have been

discovered

because of their effects in pigs,' said . Applying all this knowledge at

feed mill level, to incorporate mycotoxin control and prevention in-line,

requires that two questions are addressed, 'How can we improve the sampling

plan?' and 'Where should quality control focus?'

Future topics for research

Despite so many questions arising from the panellists themselves, there were

still plenty of topics for discussion. Biologically, there may still be more

questions than answers, especially since, over time, the concern of animal

producers also changes focus. For example, while the benefits of CLA have been

much-researched and discussed over recent years, 'we don't know how

mycotoxins might affect these, except maybe by interacting with liver

synthesis'.

Isabelle Oswald made the distinction between immunomodulation and

immunosuppression, responding to the question of whether, if they can illicit

an immune

response, some mycotoxins might have benefits. Studies with mice have found

that

mycotoxins might induce elevated levels of immunoglobulin A (IgA), but 'too

much IgA can cause kidney damage,' she said, so 'more is not always best.'

Immunosuppression is a more common and well-documented problem. Although the

discussion centred on immunosuppression and animal productivity, its effects in

humans also cause concern. As Gonzalo pointed out, mycotoxin transfer

from plants to humans via animal products is restricted to milk, so the

aflatoxin B1 regulation for dairy cow feed is designed to minimise human

exposure

to aflatoxin M1, Wayne Bryden added that 'lots of data show a huge impact on

humans,' he said, 'especially in utero, where the exposure can start and cause

later problems in children. Fumonisins,' he added, 'can also cause neural

tube defects in mice.' Mycotoxins might also affect the immune defences of

animals and humans via the intestinal microflora. However, Isabelle Oswald

admitted that although effects on the intestinal barrier have been documented

in

pigs, disrupting nutrient absorption and allowing contaminants across, no major

effects have been reported on the microflora.

Some potential solutions

Conversely, in ruminants especially, added , the microflora can

detoxify mycotoxins. Researching the biological interactions between

mycotoxins, animals, microbes and plants, may also uncover useful information

we can

use to combat them. Rudolf Krska pointed out that studying detoxification in

plants 'might identify plant mechanisms' and then 'conjugation genes might be

used to trigger detoxification in plants', he said. However, currently, plant

detoxification is causing more problems than solutions. 'These [masked

mycotoxins] are more polar compounds so they could be bound,' he said. We could

also look at bioavailability during digestion. 'Almost any sample we have

investigated of deoxynivalenol contained different levels of the glycated form.

There may be an additional seventy percent of deoxynivalenol', he warned,

adding that 'particularly resistant plant genotypes may contain higher levels

of

masked mycotoxins.' Masked fumonisins have also been identified through

research into baking, continued Krska, and a great variety have also been found

for

zearalenone. Science, in the fight against mycotoxins, does make a

difference, but in many circumstances, we are still very much in an era of

discovery.

PUBLICATION DATE: 02/13/2009

COMPANY: _Biomin_

(http://www.engormix.com/e_companies_showcase.asp?empr=496)

SOURCE: Biomin GmbH press release

Sharon Noonan Kramer

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