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Molds and Mycotoxins
by Agri-King Nutrition Department

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There are many different kinds of molds. These organisms are present in the environment around us, and will reproduce and grow whenever there is oxygen, available food sources and proper environmental conditions.

Some molds are beneficial to us, such as penicillin and antibiotics, while some molds are even used in food products, such as cheeses. However, other molds are harmful and produce toxic and undesirable chemical compounds.

On dairy farms, molds can cause large economic losses of feeds. They also can have a negative impact on animal health, feed intakes and reproduction. Adverse animal effects can come from the molds, themselves; or they can come from specific poisons, called mycotoxins, that some molds produce.

Molds grow in moist environments where oxygen is available. They grow rapidly in silages and high moisture grains that are not properly packed and sealed. Each mold cell is called a colony forming unit (CFU). Since molds are in the air, soil, water and feed, it is not uncommon to find mold counts of 10,000 CFU per gram of dry matter (DM) in feed and food. Some problems begin to occur when levels are higher than 100,000 CFU/g. The following table lists risks for mold counts in air-dried feeds:

Prevention

The best approach to maintaining low levels of molds in feeds is through prevention. Proper storage and ensiling techniques are major keys to preventing growth of molds. Ensiling at the proper moisture level, attention to particle size, rapid packing with a heavy wheeled vehicle to achieve high densities, covering bunker silos, using Silo-King to inhibit mold growth and reducing surface area during feedout are some ways to inhibit mold growth in silages.

Proper storage of high-moisture (HM) grains can be done by keeping exposed grains from contact with oxygen to the best extent possible.

Mycotoxins

Mycotoxins are produced by molds and are considered as poisons. They are most common in silages, HM grains, and stored purchased feeds. When purchasing HM grains or whole cotton seed, it is advisable to have an analysis of the feedstuffs conducted. Stopping mold growth does not eliminate mycotoxins that have already been produced. Therefore, the analyses for molds and specific mycotoxins, such as aflatoxin and vomitoxin, may be needed. It is possible to have low mold counts, while having high mycotoxin levels, and vice versa.

Some of the more common mycotoxins are aflatoxins, vomitoxin, zearalenone, DON and T2. Aflatoxin can be produced during warm, humid conditions, and is commonly found in HM corn grain, whole cottonseed or peanut products. A yellowing to greenish tint in whole cotton seeds is an indication that the seeds have been wet at some time, and may contain aflatoxin. The only way to know for sure if and/or how much toxin is present is to request a laboratory analysis. The use of a black light may show if aflatoxin is present, but it is no longer considered as an adequate detection test. Below are our guidelines for some of the common mycotoxins found. These values are based on the total dry matter intakes for dairy cattle.