Mycotoxins 101

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Source: Beef Cattle Research Council

For beef producers, mycotoxins are often a hidden problem. They are invisible, colourless and odourless. They are difficult to detect and often cause significant damage before they are identified and managed.

The source of mycotoxins most relevant to beef cattle production are fungi, including mold, that can be present in the grasses and cereals that cattle consume as feed. These fungi have the capability to produce mycotoxins when they are stressed. They do this as a defensive mechanism, with the mycotoxins meant to protect the fungi from external threats.

Virtually all feeds that comprise beef cattle rations are potential sources of mycotoxins. This includes green pastures, cereal swaths, standing corn for winter grazing, cured and ensiled grass, cereal forages, crop co-products (straw, distillers’ grains, grain screenings, oilseed meals) and commercial feeds.

It is important to note that the fungi or mold itself is not toxic to animals. The damage is done by the defensive mycotoxins, which are secondary metabolites that the fungi produce.

More than 400 mycotoxins have been identified, but only a few are regularly found in grains and seeds used for animal feed.

A few top examples of the types of mycotoxins that can be produced are:

Vomitoxin– also known as deoxynivalenol (DON), which occurs predominantly in cereal grains such as wheat, barley, corn, oats, and rye, and less often in canary seed and forage grasses. The occurrence of DON in Canada is associated primarily with Fusarium Head Blight caused by the pathogen Fusarium graminearum. Other mycotoxins which may be associated with DON are T2 and HT2, which are even more toxic than DON.

Zearalenone– Also produced by Fusarium, this less common mycotoxin is an estrogen-like compound that generally doesn’t have an effect on feeder cattle but can cause reproductive issues in cows.

Alkaloids – various types related to ergot including ergovaline, ergocornine, ergocristine, ergometrine, ergosine and ergotamine, which can contaminate cereal grains and cereal forages as well as cool season grasses. Claviceps purpurea is the fungus that causes ergot and produces these mycotoxins in purplish-black ergot bodies in the heads of the grasses or cereal grains.

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