The hidden danger in feeds - mycotoxins

These are the nasty toxins produced by moulds, which are commonly found on grains, silages, hay and other by-products used as feeds.

Unfortunately, most natural feedstuffs are susceptible to contamination.

In fact, mycotoxins are so common, they are considered unavoidable.

For producers, mycotoxins can often be difficult to detect as they may have been produced before, during and/or after harvest.

That's where Alltech's 37+ feed analysis test and the mycotoxin binder Mycosorb A+ come into play (see story below).

Often the first signs that there is a problem with mycotoxins is often only when the animals being fed experience reduced growth rates and/or increased production costs.

Cattle fed highly-contaminated feeds can suffer from digestive disorders, lower feed intake, immune challenges and increased susceptibility to disease.

Affected feedlot cattle typically display symptoms including reduced feed intake and ill thrift, excessive saliva and poor growth rates.

A compromised immunity system can also limit the animal's ability to fight disease such as BRD and cope with heat stress.

Essentially, mycotoxins fall into three broad groups - aspergillus, penicilliums and fusariums - and attack the animal's immune system.

Mycotoxins are substances naturally produced by mould and are recognised as part of a microorganism's defence system.

The big problem is that the moulds which produce mycotoxins are able to develop readily, particularly if the moisture content of the feed is above 14 per cent, temperatures are greater than 16C, and suitable aerobic conditions exist.

Mycotoxin production is also dependent on factors such as microbial competition, nutrient availability, water activity, pH, humidity, presence of bugs, and application of fungicides and pesticides.

In northern beef production systems, silage is currently presenting the greatest challenge.

Late harvest can aggravate the problem, because the longer the crops stay in the field, the more susceptible plants become to stress. In addition, problems can result from poorly stored grain or silage.

Processed feeds can also create issues. For example, mycotoxins can be present in distillers' dry grains with solubles, as the toxins are able to survive the ethanol production process.

VISUALLY, it can be very difficult to identify dangerous levels of mycotoxins in stock feeds, as there may be multiple toxins present and the contamination is often limited to only sections of the stored feedstuff.

As a rough guide orange, red and pink moulds are considered more dangerous, compared to green and blue moulds.

However, all mycotoxins can impact on productivity, and in different ways.

Feedstuffs that have historically been known to have mycotoxins include: aflatoxins in peanut hay, almond hulls and distillers' dry grains, as well as ergot in sorghum grain, trichothecene and fumonisins in corn and sorghum silages and deoxynivalenol and zearalenone in wheat and barley grain.

About 50 per cent of silage and total mixed rations samples contain penicillium or storage mycotoxins. These mycotoxins can continue to grow during storage, increasing the risk to the animal at the feedlot.

One strategy has been to mix known clean ingredients with potentially contaminated feed to reduce the level of risk of affected feeds.

Fortunately, science can provide a far better management choices.

Alltech's 37+ feed analysis test not only identifies the mycotoxins present in a feed ration, but also considers the mycotoxin challenge as a whole.

Alltech has also developed the mycotoxin binder Mycosorb A+. This binder effectively "wraps up" mycotoxins, allowing the mycotoxins to pass through the animal's digestive system.

Mycosorb A+ is also an effective way of minimising the risk of undetected mycotoxins within feed rations.

Unlike inorganic materials, Mycosorb A+ does not impair the bioavailability of nutrients in the gastrointestinal tract.

The inclusion rate for Mycosorb A+ for a low to medium mycotoxin challenge in beef cattle is 10 grams/head/day. This equates to a cost of 13c/head/day or a $10-$13/tonne inclusion cost.

- Toby Doak is a livestock nutrition advisor with Alltech Lienert Australia.