By Dr. James C. Coomer, Ph.D., P.A.S.
The word mycotoxin appears to have been first used in a publication by Forgacs and Carll (1955) where they are describing diseases of animals caused by toxins produced by fungi (microbial toxins = mycotoxin). The word usually refers to a structurally diverse family of naturally occurring, fungal-elaborated toxins.
Over 300 of these toxins have been identified, and many have been proven to cause adverse effects on livestock. We’re not going to try to identify or describe all the toxins and their effects on livestock, but rather discuss some of the new ways in which the livestock industry is attempting to deal with mycotoxins in feeds/rations and their effects on animals. Just as the technology in warfare has advanced from the carpet bombing used in World War II to the “smart bombs” used today, the efforts to deal with mycotoxins in livestock nutrition has also advanced. In WWII, planes dropped hundreds of bombs in the hopes a few would hit the desired target. Now militaries use computer-guided “smart bombs” with GPS technology to hit very specific targets with extreme accuracy.
In similar fashion, our efforts to deal with mycotoxins have gone from using broad-based, non-specific efforts to now working on more targeted specific efforts to deal with both toxins and their detrimental effects on the animal.
Prevention of mold growth on feedstuffs is a good first step in dealing with mycotoxins. If there is no mold growth, then the fungi can form no toxins and therefore cannot cause harm the animals. Fungi need moisture and oxygen to grow. Attempting to prevent mold growth on feedstuffs should start at this level.
To prevent mold growth in stored feeds due to lack of moisture, the feedstuffs (grains, by-products, or forages) need to be stored at less than 13-15% moisture, since most molds do not grow well at moisture levels below this. This level of moisture in forages can be very hard to achieve in many geographical areas due to high humidity and frequent rain.
Some organic acids or salts of organic acids (acetic, propionic, sorbic) limit mold growth. Some are, or have been, used to help preserve forages by reducing mold growth in low moisture forages. Higher moisture, fermented feedstuffs need to rely on elimination of oxygen to prevent mold growth and potential mycotoxin formation. In fermented feedstuffs, elimination of oxygen comes first from proper packing of the feedstuff. Most forages need to be packed to a density of greater than 16 lb dry matter/cubic foot. The more dense, the better.
Additionally, the use of a good forage treatment product containing an antioxidant and other fermentation enhancement ingredients (i.e. Silo-King®) can be helpful in quickly removing oxygen in the stored feedstuff, thus reducing further the ability of mold to grow.
In at least the past 30 years, the main way of dealing with a mycotoxin challenge in livestock feeding has been to add a flow agent to the ration. The reason for this was the flow agents are typically porous clay products. They are thought to “bind” the mycotoxins in the pores and prevent them from being absorbed by the animal. There is some international research that shows this approach has some limited merit, but does have some potential negative effects.
Most flow agents are nonspecific in what they bind. This results in the possibility that nutrients (vitamins, small elements) are being bound, as well, which can cause other issues. Some have attempted advancements in this approach more recently. This includes treating the clays to increase the pore size and surface area, hoping to increase the “binding” ability of the clay products. However, this does not reduce or eliminate the unintended “binding” of other nutrients.
Another more recent approach to dealing with mycotoxins has included the use of yeast cell wall components. These cell wall components have Manno-oligosaccharides (MOS) “binding” sites on the cell surface. They are thought to “bind/attach” to some mycotoxins and prevent them from being absorbed through the intestinal lining, as well. This approach is similar to the clays, but hopefully without the unintended binding of other nutrients. However, this seems to have had limited success.
Recently, there have been developments of a more targeted approach to dealing with mycotoxins. The use of enzymes to target and detoxify/denature specific mycotoxins. Recently, the United States Food and Drug Administration has provided for the safe use of the enzyme fumonisin esterase to degrade fumonisins present in poultry and swine feeds. Agri-King has introduced a new product – AKMC – containing microbes and enzymes that target specific chemical groups such as alcohols and esters, which are present on some anti-nutritive compounds such as mycotoxins. Where herds have exposure to zearalenone, vomitoxin, and other toxins, supplementation with AKMC has resulted in improved breeding and production responses.
Another recent more targeted approach has also helped the animal deal with the effects of the toxins. Deoxynivalenol (DON or vomitoxin) affects protein synthesis at the cellular level. Therefore, the addition of microbial-based nutrients that help the cells deal with this effect has also been a part of the AKMC approach to dealing with mycotoxins in livestock. The animal’s liver also detoxifies toxins and this process increases the oxidative stress to the liver cells. Therefore, the addition of nutrients to AKMC to help the animal’s cells deal with this oxidative stress is also helping the animal deal with the negative effects of mycotoxins.
Mycotoxins have been around forever and will continue to be an issue to deal with in the livestock industry. Though success in dealing with mycotoxin issues in the past has been challenging at best, new technology and approaches of dealing with both the mycotoxins directly and the effects of the mycotoxins are providing renewed hope for success in dealing with these issues going forward. AK
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