By Dr. Hans H. Stein
May 2010
With the increase in the outside temperature, it is no longer possible to keep grain stored at a temperature of 50o F or less, which means that mycotoxins can now be produced in stored grain. It is, therefore, important to continue to keep an eye on the quality of the grain coming out of the bins. It is also important to keep the moisture concentration in the grain as low as possible and preferably at less than 14% to reduce the risk of mycotoxin production in the grain. Contaminated grain needs to be cleaned and dried and, if possible, it should be mixed with non-contaminated grain before usage to reduce the level of mycotoxins in the finished feed to levels that will not cause production problems.
Mycotoxins are produced by mold that is present in the grain, but the presence of visible mold does not necessarily lead to growth of mycotoxins. On the other hand, the absence of visible mold does not guarantee that the grain is free of mycotoxins. If there is reason to believe that a certain load or bin of grain is contaminated with mycotoxins, the grain needs to be tested. The mycotoxins that are most common in the corn crop of 2009 are vomitoxin and zearalenon so the grain should be tested for both of these toxins.
If zearalenon is detected in the grain, it is advisable to keep that grain away from breeding animals; feeding of grain contaminated with zearalenon usually leads to reproductive problems. However, grain that contains up to 2 ppm of zearalenon may be fed to growing-finishing pigs. Vomitoxin in grain will lead to feed refusals, vomiting, and reduced growth performance even at levels as low as 2 ppm. If the concentration of vomitoxin is at or above 2 ppm, contaminated grain needs to be blended with non-contaminated grain. The complete feed should contain no more than 1 ppm vomitoxin, so the amount of contaminated grain that can be accepted in a diet depends on the concentration of vomitoxin in the grain.