Mycotoxins and Ruminants

Ruminants consume feed that is likely to be contaminated with mycotoxins.  Mycotoxins are extremely widespread in all feeds including in grains, maize and forage.  Including derivatives and metabolites, there are over 500 different mycotoxins.

It is widely accepted that ruminant diets are frequently contaminated with multiple mycotoxins.  When present together, these toxins can act synergistically, increasing their risk.

Complex diets and feed transitions that combine forages, by-products and fermented feeds all present a risk to ruminants.  Straw and other grown bedding materials can also be a source of mycotoxins.

Most symptoms of mycotoxin contamination come from sub-acute effects: lower productivity, growth rates, feed conversion, milk volume, fertility or higher disease incidence.

Livestock can never reach their full potential when affected by mycotoxins.  At worst, milk and meat may be unsuitable for human consumption by exceeding regulatory levels allowed into the food chain.

Know Your Risk, Take Control

Sources of Mycotoxins

Complex feed systems like TMR, commonly used for dairy ruminants where forage, grain and other processed feeds are combined, present a significant risk of multiple mycotoxin exposure.

Such feeds are commonly found containing Deoxynivalenol (DON), Zearalenone (ZON), and Fumonisins (FB1 and FB2), and can manifest as chronic health issues affecting performance and productivity.

Chopped Forage


Forages are frequently found infected with Fusarium and Aspergillus fungi.

As a high energy crop, maize is at high risk of becoming contaminated with Aflatoxin and Fumonisin mycotoxins.

Wheat Grains

Cereal Grains

Grain is often contaminated by Fusarium fungi, which favour cooler and wetter conditions.  Fusarium species are known to produce Trichothecene and Fumonisin mycotoxins.

Straw Bale


Straw, a common feed and bedding material, is frequently overlooked as a source of mycotoxins.  The fungi responsible for causing producing mycotoxins in grains can also infect the plant stems.

Results from our 2018 straw survey show that straw is frequently contaminated with multiple mycotoxins.

Effects of Mycotoxins in Ruminants

Common symptoms of mycotoxins in ruminants could include the following:

Reduced milk production

Milk quality affected

Udder health issues

Impaired rumen function

Poor growth and reduced body weight

Immune suppression

Abortions and reduced fertility

Skin lesions

Liver and kidney damage

Locomotion issues

Foot health

Faecal stability

Specific symptoms associated with the main mycotoxins are provided below.

Aflatoxins are of particular concern to the dairy industry.  AFB1 a potent carcinogenic toxin, is metabolised by the liver to AFM1, which is also carcinogenic.  AFM1 can pass in to the milk and go on to cause serious human health issues.  For this reason, AFM1 levels in milk are heavily regulated around the world1.


1.  Commission Regulation (EC) No 1881/2006

The ability of the rumen to detoxify Fumonisins is less than for other toxins2.

Fumonisins are known to cause damage to the liver and kidneys3.


2.  Fink-Gremmels, J. (2008). Mycotoxins in cattle feeds and carry-over to dairy milk: A review. Food Additives & Contaminants: Part A, 25(2), 172–180.

3.  Hussein, H. (2001). Toxicity, metabolism, and impact of mycotoxins on humans and animals. Toxicology, 167(2), 101–134.

DON is the most prevalent mycotoxin in ruminant feedstuffs.

Although ruminants are generally less susceptible to acute trichothecene toxicosis, the impact of chronic effects can be significant4.

Gastrointestinal problems, diarrhea, and poor growth rate can all occur as a result of feed refusal5.


4.  Morgavi, D. P., & Riley, R. T. (2007). An historical overview of field disease outbreaks known or suspected to be caused by consumption of feeds contaminated with Fusarium toxins. Animal Feed Science and Technology, 137(3–4), 201–212.

5.  Fink-Gremmels, J. (2008). The role of mycotoxins in the health and performance of dairy cows. The Veterinary Journal, 176(1), 84–92.

ZON mimics oestrogen, and as a result can cause reproductive issues such as poor milk yield, lower conception rates, or even abortions.

ZON is commonly found occuring together with DON in feed samples.


6.  Zinedine, A., Soriano, J. M., Moltó, J. C., & Mañes, J. (2007). Review on the toxicity, occurrence, metabolism, detoxification, regulations and intake of zearalenone: An oestrogenic mycotoxin. Food and Chemical Toxicology, 45(1), 1–18.

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