21 Sep 2020

Why it’s difficult to detect high levels of mycotoxins in clinical mycotoxicosis



Manuel Contreras

Diamond V

Content available in: Español (Spanish)

Traditionally, veterinarians and professionals who work in animal production have been trained to isolate or detect the causative agents of the clinical cases reported in poultry facilities.

Identification is often achieved by replicating the clinical signs of disease or poisoning observed in animals.

In the case of toxins, some feed factories often maintain experimental poultry sheds where they can test whether a nutritional ingredient or contaminant is causing the reported poisoning.

  • Although mycotoxins are not living microorganisms, but rather metabolites produced by fungi when they grow, we tend to try to conclusively detect which is the etiological agent.
  • In other words, to demonstrate that mycotoxins were indeed present in the feed consumed by the affected animals.

Unfortunately, it is not always possible to identify the mycotoxins that caused different symptoms or lesions in the animals after seeing a case that we consider typical.

There are many reasons preventing us from reconfirming the relationship between what we see in the field and the presence of mycotoxins in the analysis, namely:

  1. Irregular distribution of mycotoxins in grains and feed.
  2. Errors in taking samples.
  3. Laboratory techniques used to do the analysis.
  4. Presence of conjugated or masked mycotoxins.


Unlike the protein or moisture content in corn or soybeans, mycotoxins are not evenly distributed. The main reason is that fungi don’t grow everywhere, only in specific places.

This trend can start in the field.

Some grains can contain high levels of mycotoxins while others do not.

At the level of feed factories, especially in the silos, fungi grow mostly where humidity is more prevalent, also known as “hot spots”.

  • These points have been identified for decades and occur via the movement of moisture from the silo’s exterior and mostly at night when ambient temperatures drop.
  • The changes in temperature produce condensation on the internal walls of the silo, which promote the growth of fungi.

The same phenomenon can occur in trucks, boats and other compartments where grain or feed gets stored.


A correct analysis means determining the average contamination of within a batch of grain or formulated feed. If proper sampling procedures are not followed, analytical results are likely to underestimate the true mycotoxin concentration.

  • That is, if only areas with low or no contamination are sampled, no real results will be obtained.
  • False negative results can occur in tests, as a result of inadequate sampling and poor preparation of the sample to be tested.
  • When few incremental samples are taken or the total lot sample is too small, it is much more common to “lose” a contaminated grain than to “find” it.

The chances of identifying mycotoxins in feed increase if they are taken from feeders located on farms, because that feed has been stored inside the silos for about 5 to 7 days and about a day inside the house once it is transferred to the hoppers and then to the feeders (if they are automatic).

The length of time that the feed remains on the farms depends on the management in the company and the type of birds housed.

Unfortunately, even in clinical cases of mycotoxicosis where affected animals show typical lesions and where samples are taken in the right way and in the right place, we often do not identify mycotoxins during testing.






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