[STELLENBOSCH] - Mycotoxins are substances naturally produced by moulds and fungi that are normally present as some form of defence for the organism against any threats of some sort. The growth of moulds and fungi are typically encouraged by heat and the presence of moisture, however their toxin production is dictated by other factors that induce stress, including drought.

Toxins are naturally produced by all types of moulds and fungi. Although mycotoxins are unavoidable contaminants of cereal grains, being aware of the contamination possibilities and taking proactive steps will go a long way in managing their impact.

Good management plays an essential role to limit the potential growth of fungi and therefore toxin production. It is however, difficult and essentially impossible to guarantee that feed or any other natural occurring materials will be mycotoxin free.

The source of mycotoxins:

Types of Mycotoxins and affects

Many different mycotoxins have been found to accumulate in feed sources but certain toxins are more commonly found in feed and cause various effects on animals.

Commonly analysed mycotoxins include:

Deoxynivalenol (DON/vomitoxin) - have been associated with nausea, vomiting, diarrhea, feed refusal and a drop in milk production in dairy cattle.

Zearalenone - can have reproductive effects in ruminants, and pigs

Fumonisin B1 - cause feed refusal and pulmonary edema in swine and ELEM* in horses.

*Equine leukoencephalomalacia (ELEM), commonly called “Moldy Corn Poisoning”, is a disease of the central nervous system that affects horses, mules, and donkeys.  It is commonly associated with feeding of moldy corn over several days to weeks.

Aflatoxins - cause an increase in mortality rates, weight loss in animals, a decrease in egg production in poultry and a drop in milk production in dairy cattle.

Ochratoxin - have been associated with increased mortality, a decrease in weight gain and a decrease in egg production in poultry.

Prevention

It is very important to note that the toxins already start in the field and to reduce toxin production it is important to start with managing decisions that support plant health. It is therefore safe to state that it is better to prevent these mycotoxins from occurring in the feed than to treat the animals affected by these toxins.

Prevention can be implemented before harvest with good management of the crop, harvesting and storage. It must be noted, however, that prevention does not remove mycotoxins that are already present and therefore animals can still be affected.

Preventative measures include but not limited to:

• Irrigation can reduce plant stress and deter aflatoxin-producing fungal species. However, avoid irrigation directly during anthesis for wheat and silking for maize since splashing is a significant way in which fungal spores are transferred onto a plant. These growth periods are when the plant appears to be highly susceptible to infection.

• Crop rotation among a host (maize) and non-host plant (such as soybeans) is also a good option. If the fungus has a host crop that it likes to colonize every year, it will build up high populations. But rotating a less ideal host plant with a good host will limit its growth.

• Insect management is important because they can carry spores on their bodies and into the plants, spreading infection. Insects also attack the plants which make the plant more prone to fungal growth and therefore toxin production.

• Cross-breeding and hybrid selection of crops can help in areas with aflatoxin contamination.

• The fungi like to grow down the silk of maize; tight-husked hybrids have been effective in reducing fungal colonization.

Testing for mycotoxins

The increased incidence of mycotoxin contamination is not only due to an increased prevalence of mycotoxins, but also because of improved analytical methods to detect them. The first and most crucial step in mycotoxin analysis is sampling of raw materials or feed. Mycotoxin contamination can be concentrated in so-called ‘hot spots’, while other parts of the batch are not contaminated at all.

Mycotoxin levels can increase rapidly in high-moisture grain. One important factor to remember is that mycotoxins are not distributed evenly in grains, and typically occur in hot spots of contamination. This may be a result of actual heating that occurred in a certain area of stored grain, which promoted fungal spread and mycotoxin production in that isolated region.

During storage, drying is a critical point where contamination can occur. The more time that passes between harvesting and drying, the shorter the allowable storage time for that grain. Drying too quickly or at high temperatures can cause stress cracks in the grain, which are prime entry points for storage fungi.

Temperature is another important factor during storage. At cool temperatures, fungi grow very slowly and many storage insects and mites are dormant.

Pests can cause kernel damage and create hot spots, so it’s important to control the presence and activity of rodents, birds, insects and mites. Insects can transport spores from an initial contamination site to other sites they contact.

Between grain loads, bins should be thoroughly cleaned of residual grain and fines which may contain contamination from the previous lot.

Stored grain should be checked often for signs of spoilage. Twice a week is not unreasonable, especially during seasons with high-risk of warming or moisture accumulation and day/night temperature extremes.

Signs to look for are an off-odor; crusted, colored or wet grain on the top surface of the bin; signs of pest activity; and temperature changes.

Alltech’s MIKO on farm

Alltech’s MIKO (mycotoxin hazard analysis program), based on HACCP (Hazard Analysis Critical Control Points) principles, is a systematic audit used to evaluate and identify ways to reduce areas of future mycotoxin risk. This involves establishing the correct cleaning and monitoring procedures as well as identifying critical levels for animals.

Alltech’s 37⁺ Program uses the most advanced mycotoxin testing techniques available to producers and offers a more in-depth picture of their mycotoxin risk.

Mycotoxins are harmful to animals and can greatly affect their performance and productivity. Because of the wide range of mycotoxins, with different chemical structures, a single approach cannot efficiently solve the problem.