You are viewing Sub-Saharan Africa

Ruminants Mycotoxin Management

Importance of Mycotoxin Management in Ruminants

Just like all livestock, ruminant animals require high quality feed and bioavailable essential nutrients in order to grow into healthy animals with optimum production and reproduction qualities. While weather and harvest conditions aren’t always favourable, farmers are under severe pressure to deliver quality home-grown forages to reduce the costs of buying extra feed. It is therefore essential to control the growth of mould and wild yeast. If left untreated, mycotoxins can develop, which could give rise to many different pathological effects such as toxic livers and kidneys, defects of the central nervous systems and estrogenic responses.

These pathologies lead to lower animal performance, productivity and elevated FCR (Feed Conversion Ratio). While poor animal performance is of economic importance, the effect of many mycotoxins on the immune system is of increased concern. Mycotoxins can impact the susceptibility of animals to viral, bacterial and parasitic diseases and can have a negative impact on the intestinal morphology and function, which can compromise the gut health of ruminants.

What Are Mycotoxins?

Mycotoxins are toxic secondary metabolites produced by some mould species when the moulds are stressed (e.g. when the moulds are in competition with other moulds). Mycotoxins are invisible, colourless and odourless and often go completely unnoticed as a result thereof. Mycotoxins can be present even when moulds are not visible. Mycotoxins are often only identified and managed after significant losses have already occurred. The production losses (especially in milder cases) are often not considered and may significantly impact a farmer’s economic returns.

Some raw materials have higher risks for specific mycotoxins and different mycotoxins have different effects on ruminants. Factors such as age and stress also affect the impact of mycotoxins on ruminants. Immature animals and animals under stress (e.g. adaptation and heat stress) are often more sensitive to mycotoxins than mature animals under low stress conditions.


Factors That Contribute to Mycotoxin Risks

High moisture raw materials and feeds have a higher risk for mould growth and are therefore also a higher risk for mycotoxins. Higher temperatures also promote mould growth, hereby increasing the risk for mycotoxins. Mycotoxin occurrence is often seasonal due to the effect of moisture and temperature on mould growth.

Raw materials that carry a significant risk for specific mycotoxins

Aflatoxins and ochratoxins are often found in protein-rich raw materials such as peanuts, cottonseed, soya, maize products and by-products. In the samples we analysed in our laboratory we detected Trichothecenes (DON, T2 and HT-2 Toxins) mostly from forage products, maize and wheat bran. Zearalenone seems to be common in forage products such as silage, grass and hay, as well as in soya, maize and wheat bran products. Fumonisins are especially common in maize and maize products as well as forages such as silage and hay.


Aflatoxins are potent hepatotoxins and strong carcinogens. Aflatoxins also affect immune function, potentially resulting in disease outbreaks and interfering with vaccine-induced immunity as well. Animals consuming feed contaminated with aflatoxins may show reduced growth rates and higher FCRs as well as fatty livers, lethargy and a rough hair coat. Aflatoxins are particularly important to dairy animals as Aflatoxins can be converted to Aflatoxin M1, which is excreted in milk. Aflatoxins are produced by Aspergillus species such as A. flavus and A. parasiticus.

Studies have shown that Fumonisins are poorly degraded by the rumen. If Fumonisins are consumed for prolonged periods clinical signs include decreased appetite, liver damage, kidney damage and reduced immunity (decreased lymphocytes). Fumonisin B1 can significantly affect the intestinal integrity and mucus production, increasing intestinal permeability. Fumonisins are produced by Fusarium moulds such as F. proliferatum and F. verticillioides.

Zearalenone is an important mycotoxin to note with regards to breeding animals as it affects the reproduction system. Zearalenone is converted to α-Zearalenol (90 %) and β-Zearalenol (10 %) in the rumen. α-Zearalenol is more toxic (oestrogenic) than Zearalenone while β-Zearalenol is less toxic than Zearalenone. Clinical effects of Zearalenone ingestion includes reproductive problems such as oedema of genitalia, decreased embryo survival, decreased hormone production (luteinising hormone and progesterone) as well as general infertility. Zearalenone is produced by Fusarium moulds such as F. graminaerum.

Ochratoxin A is a strong nephrotoxin (affecting the kidneys) leading to kidney damage, weight loss and general weakening. Ochratoxins have been documented to have immunomodulatory properties leading to increased disease susceptibility as well as carcinogenic properties. Ochratoxins are seldom a problem for ruminants as the rumen can effectively convert Ochratoxin A to Ochratoxin α, which has a lower toxicity level. Ochratoxin levels may however exceed the rumen’s detoxification capacity in severe cases. Ochratoxin A is produced by Aspergillus and Penicillium mould species.

Ruminants are generally less susceptible to trichothecenes. DON has been showed to be well degraded in the rumen to less-toxic compounds. Trichothecenes affect digestion, resulting in weight loss, skin problems and intestinal bleeding. Trichothecenes also affect the immune system and can inhibit protein synthesis. The trichothecenes are all produced by different Fusarium mould species such as F. sporotrichioidesF. graminaerumF. poae and F. culmorum.

The Potential Effects of Mycotoxins On Ruminants

Ruminants are typically less sensitive to mycotoxins than monogastric animals due to the rumen’s capacity to degrade some mycotoxins to less toxic metabolites. Fumonisins and patulin are however not well degraded in the rumen and Zearalenone is mostly metabolised into more toxic metabolites. In cases where animals are immune compromised, stressed or undergoing diet changes the rumen may not be able to degrade mycotoxins very well. Mycotoxin intake levels can also exceed the rumen’s capacity to degrade mycotoxins. Diet composition can affect the rumen’s capacity to degrade mycotoxins as the microflora responsible for the mycotoxin degradation can be affected by the diet composition. A study showed that grain-fed sheep have a significantly lower capacity of rumen degradation of mycotoxins compared to sheep that consume hay.

How to Prevent and Manage Mycotoxin

It is important to monitor and address mycotoxin risks by discarding mouldy raw materials or feeds. Buy raw materials from reputable suppliers and ensure that the moisture is within acceptable levels. Perform tests from time to time, especially on high risk raw materials/feeds.

Furthermore, ensure that final feed moisture levels are within allowable levels to limit mould growth during storage.