Mycotoxin contamination: assessment of risk in livestock systems

Summary

Results:

The study found that the main groups of mycotoxins that effect ruminant health and performance include aflatoxins (AFL), fumonisins (FUM), ochratoxin A (OTA), trichothescenes (TRIC) and zearalenone (ZEN).

Mycotoxins can be found in grain (during growth and storage), silage and straw and production is influenced by environmental conditions including pre and post-harvest temperature, agronomic practice and carbon dioxide and moisture levels. The report demonstrated that good agricultural and storage practices are the best ways to control and prevent mycotoxin contamination of feedstuffs and subsequent exposure to livestock.

High levels of the mycotoxin Deoxynivalenol (DON) have been found after all forms of agronomy. DON is produced by Fusarium mould as a result of Fusarium head blight infections in the crop. Maize is a major host for the mould Fusarium, therefore crops following maize are much more likely to be contaminated with the mycotoxin. Cultivation method was also found to influence mycotoxin production, with DON concentrations being ten times higher when min-till rather than ploughing was used. This reduction in DON was linked to a reduction in crop residue left on the soil surface. A short delay in harvest has little effect on mycotoxin production but a longer delay with an extended ripening phase due to wet weather can result in large increases in Fusarium mycotoxins.

The amount of mycotoxins produced during storage is dependent upon the moisture content and the temperature of stored grain. Mycotoxin production cannot occur once the moisture content of the grain is below 15%, therefore it is important that grain is dried and cooled as soon as possible after harvest. Some mycotoxins, including OTA, are not produced on the growing grain but the mould that produce them can survive between harvests on old grain and dust present on machinery and stores. To reduce the risk of OTA it is recommended stores and machinery are cleaned thoroughly before each new crop is harvested.

The report showed that straw can contain more mycotoxins than grain, in particularly the mycotoxins DON and ZEN. In the delayed harvest of 2008, nearly 50% of straw samples exceeded the feed guidance limits for DON and ZEN. Levels of mycotoxins can vary greatly between bales harvested from the same field and this could result in intermittent mycotoxin issues on farm. To reduce the risk of mycotoxin contamination, straw should be harvested and stored undercover as soon as possible.

To minimise mycotoxin content of silage it is crucial that the crop is ensiled at the optimum moisture and the harvested crop is compacted. It is also important that the silage is covered properly so that oxygen cannot get into the silage as this can cause fungal growth and mycotoxin production. When feeding clamped silage it is recommended that the silo front is systematically removed so that no one area remains exposed for long periods of time. For baled silage it is important to correctly handle bales to avoid damage to the plastic wrapping and to avoid pest damage.

A substantial number of commercial mycotoxin binders are available on the market, however very few provide detailed information concerning their alleged efficacy. Currently, only one product is approved for use as a mycotoxin binder by the European Food Safety Authority (EFSA), it is bentonite and is approved for ruminants, pigs and poultry. Surveys of vets and farmers showed that the use of binder products appears to be considerably varied within the different livestock agricultural sectors. The cattle industry uses binder products as part of treatment based protocols when suspicious of mycotoxin exposure. In contrast, the pig industry has more of a prophylactic stance, with mycotoxin binders often being used all year round in the adult breeding herd.

This research has identified a number of research gaps including the need to carry out surveys of UK feed materials to determine mycotoxin levels, the need to establish more accurately animal intake of straw bedding and research on levels of mycotoxins in pasture. Toxicity studies on lower levels of mycotoxins as well as the effects of mixtures are needed and coupled with this there is a need to develop diagnostic analytical methods that measure biomarkers or markers of effect rather than parent mycotoxin. Finally, controlled studies on binders in real situations would be of benefit to produce conclusive evidence of their efficacy.

Sector:

Beef & Lamb

Project code:

74110

Date:

01 May 2014 - 31 October 2014

Funders:

AHDB Beef & Lamb

AHDB sector cost:

£42,845

Total project value:

£42,845

Project leader:

Food and Environment Research Agency (Fera)

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About this project

The Problem:

Mycotoxins at high concentrations can have a direct impact on animal health and welfare. Such conditions are rarely seen in the UK. However, at lower concentrations mycotoxins can impact on livestock performance such as decreased litter weights and reduced feed conversion rates, all of which have a direct effect on farm profitability.

Currently, the main information source for livestock farmers are companies with a vested interest in the sale of mycotoxin binders/absorbents/biotransformation microbes/enzymes.

More information is required to be able to provide independent advice for farmers on the prevalence of mycotoxins, risk factors and mitigation strategies.

Aims and Objectives:

The aim is to carry out a three-stage, desk-based review research project. This will be carried out by a consortium of researchers with experience of mycotoxins, cereal crops/agronomy and livestock (veterinary and husbandry).

The review will cover methods for testing mycotoxins in feed, forage, bedding and animals; potential effects on different species with a view to formulating prevention and mitigation strategies in order to reduce mycotoxin exposure effects.

The overall aims are:
1. To determine the severity of the mycotoxin problem in the UK.
2. Highlight research gaps.
3. Formulate mitigation advice for farmers.
4. Collate evidence for regulatory processes.

Approach:

1. Carry out a full literature review of published peer-reviewed literature, legal standards, and grey literature to cover: methods for testing mycotoxins in animal products, feed, forage straw and live animals; potential effects of mycotoxins, including species specific indicators of exposure, tolerance levels and synergistic effects of multiple mycotoxins, and prevention strategies, including but not limited to a review of commercial binders on the market.
2. Collect anecdotal evidence and mycotoxin incidents information from a range of industrial and farming sources, as well as other stakeholders e.g. AHDB, BPEX.
3. Review and assess the collected information objectively to ensure its quality, and from this collate the information into a final project report that summaries the UK situation with respect to mycotoxins in livestock, highlights research gaps and makes clear recommendations to industry to mitigate the mycotoxin risk to livestock.
4. Prepare a manuscript of the literature review with recommendations for submission to a peer review journal.
5. Produce a series of 1-page key recommendation fact sheets for farmers.