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Mycotoxins in Dairy Cows

What are mycotoxins?

Mycotoxins are harmful, naturally occurring substances produced by certain molds (fungi). These fungi commonly grow on feedstuffs and tend to multiply during adverse weather conditions. More than 500 mycotoxins have been identified to date, and this number is steadily increasing.

Mycotoxin threat to ruminants

Ruminant animals are generally considered to be less susceptible to mycosis than monogastrics. This is thought to be because rumen flora degrade and inactivate in-feed mycotoxins. However, several mycotoxins resist rumen breakdown, and ruminants must often deal with a myriad of challenges because their diet contains both concentrates and forages. Transition cows are particularly sensitive to molds, fungal spores and mycotoxins.

Mycotoxin sources

The presence of mycotoxins in forages such as grass, hays and silage poses the greatest threat to dairy cattle. Even fresh grass can be contaminated with several mycotoxins. These typically include fungal endophytes that produce mycotoxins, which protect the plant in some way, such as ergovaline and lolitrem B, as well as Fusarium mycotoxins, such as zearalenone or deoxynivalenol (DON).

The range of mycotoxins

Mycotoxins rarely occur in isolation. It is not uncommon to find multiple mycotoxins in finished feed, which allows for interactions between them, thereby leading to synergistic or additional effects.

For more information on specific types of mycotoxins and related complications, visit

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Mycotoxin syndrome in dairy cattle: characterization and intervention

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Mycotoxin symptoms in dairy cows

The signs can vary depending on the specific type of mycotoxin, the dose ingested and the period of exposure, but they may include:

  • Immunosuppression
  • Decreased feed intake
  • Reduced milk production
  • Weight loss
  • Impaired rumen function
  • Liver damage
  • Acute mastitis
  • Lower conception rates
  • Abortions
  • Lameness
  • Diarrhea
  • Ketosis

Managing mycotoxins in dairy cows

Reducing exposure to these harmful substances is key. Detection, prevention and mitigation are critical for an effective mycotoxin management strategy.

Regular analysis of feedstuffs can help to uncover potential hidden threats from mycotoxins. It is worth noting that a highly contaminated sample does not mean that the entire crop is bad. Similarly, a “clean” sample does not guarantee that all of your feed is mycotoxin-free.

Proper mycotoxin management is essential in order to avoid unpredictable losses and maintain a high-producing herd.