Aflatoxins in Asia Pacific

By Kaori Nishide

What are the latest trends of aflatoxin occurrence in the region?

Asia Pacific is strongly affected by aflatoxins, particularly South- and South East Asia. The warm and humid climatic conditions favour Aspergillus mould growth and aflatoxin production. Moreover, as Asian countries import corn and DDGS from the USA, the last year’s drought in the USA resulted in a higher occurrence of aflatoxin-contaminated imports. It is known that about two thirds of all cereals, by-products and finished feed in South- and South East Asia are – to a varying extent – contaminated with aflatoxins.

How do feed millers and farmers deal with contaminated feed?
Feed millers and farmers can discard grains that show obvious signs of mould. However, the problem is that corn can be contaminated without any obvious signs. It is impossible for feed millers and farmers to recognise this contamination only visually. Some commercial feed companies and integrators do their own mycotoxin analysis to monitor the respective levels.

But no one analyses mycotoxins in each batch, at best they do it on a routine basis. Many feed millers do not even have the necessary analytical equipment, neither do farmers. Hence, contaminated ingredients or feed are used until farmers realise reduced performance of their animals. The addition of an aflatoxin binder to compound feed is a powerful tool for compound feed producers to reduce risks to animal health and performance.

What are the risks of aflatoxin-contaminated feed?
Aflatoxins are the most dangerous mycotoxins found in feed grains, and the most prevalent ones. In livestock aflatoxins cause lesions, pale and enlarged liver, bruising legs and breasts, as well as leg weakness. Furthermore, aflatoxins reduce absorption of fat, including fat soluble vitamins. And aflatoxins impair the immune system of livestock making them more susceptible to infections. Young animals are more sensitive than adult animals. Aflatoxin residues can occur in milk, eggs, and meat. In humans, aflatoxins can lower immunity and cause cancer. In summary, aflatoxins pose major food safety issues.

Which options do we have to prevent the contamination or minimise the impacts on animal health in the region?
The best method for inhibiting mould growth in feed and ingredients is to apply a propionic acid-based product. As soon as they are added to feed or grains, propionic acid-based products immediately kill moulds and mould spores and thus prevent formation of the toxins. Propionic acid-based products can also prevent recontamination of moulds, if a sufficient amount is applied. With the right dosage in feed or grains, these organic acids can continuously inhibit mould growth and prevent re-contamination. It is also important to keep the moisture content of feed or grains below 13%. Without sufficient moisture, mould growth is inhibited.

However, this method does not work equally well in humid environments. During the rainy seasons and in high-humidity environments, feed or ingredients can absorb moisture from the air, causing moisture to increase to a level that supports mould growth. Using heat to kill moulds and mould spores is another option. It can destroy them in feed or grains.

However, even after heat treatment, mould can still grow in feed or ingredients when the conditions are met. Heat treatment also cannot prevent re-contamination with moulds. If mycotoxins are already present in the feed or the grains they remain unaffected by treatment with organic acids, moisture control, or heating. In such a case, or in the event of potential problems or doubts, a mycotoxin binder can be a good solution. The most effective clay is a pure calcium bentonite, which allows effective binding of aflatoxin, based on its interlayer structure in contrast to sodium bentonite or zeolite, which does not exhibit such a favourable structure.