Molds and Mycotoxins

Knowledge Nuggets

• Low levels of molds cause relatively minor problems. Moldy feeds are less palatable and may reduce intake. This in turn leads to reduced weight gains or milk production. Performance losses of 5 - 10% are typical with moldy feeds even in the absence of mycotoxins.

• Moldy feed may have reduced digestibility and energy content is down by 5 to 10%. Molds grow and propagate using energy from the feed. In particular, dietary fat is reduced in mold infected feeds.

• Moldy feeds may cause health problems such as mycotic abortions and respiratory disease. Feeding cattle moldy feeds may also be hazardous to humans by breathing in mold spores.

• Mold spore counts may under estimate the amount of mold present and be a poor indicator of the potential risk.

• Ruminants are less affected by molds and mycotoxins than swine because they are able to detoxify or transform mycotoxins to other often less harmful metabolites. Ruminants are nevertheless susceptible to the deleterious effects of molds and mycotoxins.

• Young pre-ruminant and high producing and or pregnant cattle are the most susceptible to the effects of mycotoxins.

• If molds and/or mycotoxins are present, it is prudent to take steps to limit their potentially harmful effects. Once the levels of mycotoxin are determined, dilute the feed with clean feed to a level that is tolerant by the cattle receiving the feed.

• Within days or weeks, the effects of mycotoxin consumption on performance becomes pronounced. Cattle may go off feed and ketosis and displaced abomasum problems may arise. Some animals develop diarrhea or have signs of bleeding. Estrogenic effects such as swollen vulvas and nipples and vaginal or rectal prolapses may occur. Reduced fertility or abortions may also be evident.

• The severity of mycotoxin problems in cattle from field cases are not readily replicated in controlled research trials. Research and field data on the effects of molds and mycotoxins are highly variable and often contradictory.

• Moldy feed does not always contain harmful mycotoxins or may contain mycotoxins but not at harmful levels. Effects of molds and mycotoxins on ruminants are highly variable in practice and are impossible to predict.

• Ruminants are uniquely equipped to protect themselves from the harmful effects of mycotoxins by sufficiently degrading the mycotoxins before they are absorbed into the blood and vital organs. However, the rate of detoxification differs for the different types of mycotoxins and the extent of detoxification of any particular mycotoxin depends on the rate of passage of feed, and the original dose level. The altered metabolite(s) may be more toxic than the original mycotoxin.