In association with Poultec Training Ltd

 A wet harvest often sparks warnings of an elevated mycotoxin risk to poultry. HGCA's Simon Hook looks at the risk and Premier Nutrition’s Steve Pritchard covers testing.

Mycotoxins are toxic chemicals produced by specific fungi that infect cereal crops. When present in sufficient quantity, they can impair flock performance and even lead to bird death.

Different fungal species produce mycotoxins of widely varying toxicity to humans and animals. Mycotoxins linked to the growing crop fall into the fusarium species category, while the penicillium species can invade stored crops.

Which mycotoxins can be found in the growing crop?

In the field, the fusarium species can infect the ears, particularly when the weather is warm and wet at flowering. One common transmission route is from spores lying on the ground in trash from the previous year’s crop. It can be splashed upwards to the ear by rainfall.

There are a number of fusarium species that infect cereals and may cause head blight. The two that are linked to mycotoxins in the field are F culmorum and F graminearum.

Probably the best known fusarium mycotoxin is de-oxynivalenol, more commonly known as DON. Another harmful mycotoxin that can be found in growing crops is zearalenone.

How do I know if my crop is infected?

Crops that become infected and show symptoms of head blight may have individual bleached spikelets, or partially bleached ears. At harvest, this can result in pink or white shrivelled grains. However, it is possible for mycotoxins to be present without seeing discoloured grains.

Which mycotoxins do I need to watch out for in store?

The only mycotoxin that is likely to develop in store is Ochratoxin A. It is produced by the storage mould, Penicillium verrucosum.

I grow my own feed crops, how can I minimise risk?

Producers should carry out an assessment of the likelihood of fusarium mycotoxins by performing a risk analysis. This can be done using the HGCA’s risk analysis tool.

Is there anything I can do to avoid contamination in stored crops?

The greatest risk to stored crops occurs during harvest backlogs and if grain is not dried rapidly. Only some strains of Penicillium verrucosum produce Ochratoxin A, and even when the fungi are present, toxins are not always produced.

As long as grain is dried rapidly to below 18% moisture content, there is almost no risk of the crop containing mycotoxins. The incidence of Ochratoxin A in UK crops is very low.

Are mycotoxins covered by legislation?

EU legislation sets out permitted levels of de-oxynivalenol and zearalenone in grain for human consumption. However, only recommended guidelines have been issued for levels in crops for animal feed.

Are mycotoxins becoming an increasing problem?

According to most experts, mycotoxins do not pose a serious threat to flock health, although the situation is being monitored on a regular basis.

They may be present in a high proportion of the crop, but at such low levels, there is no real cause for concern. However, EU legislation prohibits the blending of affected grain, in an attempt to dilute toxicity.

Do I need to worry about my pelleted feed?

Mycotoxins are generally heat stable, which means they are likely to survive heat treatment during the pelleting process.

Bought-in feedstuffs may be contaminated, but there is also a risk that poor on-farm storage facilities – either non-watertight bins and/or high levels of condensation – can create an environment that allows them to develop.

Is there a test to show whether they are present?

It is worth testing for mycotoxins in both grain and pelleted feedstuffs, if other aspects of flock management have been ruled out.

Rapid kit tests are available to detect mycotoxins in poultry feed, or samples can be sent off to the nearest accredited laboratory for testing.

The cost of testing a representative sample weighing 100-200g is about £100. However, if the sample is shown to be positive, further exploration will be needed to define which one is present.

UK labs will routinely screen samples for: Aflatoxin (B1, B2, G1, and G2), Ochratoxin A, T2 toxin, Vomitoxin (DON) and Zearalenone.

How do mycotoxins affect birds?

While surveys have shown that myco-toxins can be present in a high proportion of cereal samples, they rarely exceed levels likely to cause problems in feed.

The EU has calculated a series of guidance values (see table) for best practice. If concentrations do reach the problem level, birds can exhibit a range of symptoms such as reduced growth rates, a fall in egg production, poorer shell quality and increased water intakes.

However, a long duration of a low dose could have the same adverse effect as short exposure to a high dose.

HGCA advice

• Crop debris is a major source of fusarium. Complete burial by ploughing reduces risk to the greatest extent, with risk at its highest where direct drilling methods are used.
• Choose a variety that has low susceptibility to fusarium ear blight.
• Applying a T3 fungicide that is recommended for combating fusarium and/or mycotoxin production can reduce risk.
• More reliable fusarium head blight control may be achieved by angling nozzles backwards.

Want to know more?

HGCA mycotoxin risk assessment tool.

HGCA Topic Sheet 102 – Managing fusarium mycotoxin risk in wheat intended for human food, harvest 2008

Mycotoxin information website, sponsored by Alltech 

Food Standards Agency