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The unseen challenge of mycotoxins

What are mycotoxins?


Mycotoxins are toxic elements produced by moulds when the mould itself is stressed or as a defence mechanism of the moulds. There are very many types of moulds and mycotoxins but there is a limited number that generally affect ruminant animals.

We tend to think that if we can see mould there could be mycotoxins, and that if we can't see them, there aren't any mycotoxins, unfortunately it’s not quite that simple.

Mycotoxins are produced by actively growing moulds. It is worth noting that some moulds may be actively growing but won't produce any mycotoxins. Conversely, mycotoxins may be present at high levels when mould cannot be readily detected.

Conditions that increase the risk of mycotoxins

There are a range of conditions that can cause moulds to develop and increase the risk of mycotoxins being released:

Plant and harvest stress
This could include drought and temperature extremes including wet humid conditions which encourage fungal mould growth, disease, delayed harvest of grass with rotting at the base of the sward, soil contamination and soil borne bacteria, heavily stressed maize and slow clamp filling with poor consolidation.

Storage stress
Examples include silage clamps where air remains in the forage from poor consolidation and sheeting, silage with a poor fermentation and high pH with low lactic acid levels, forage with too high dry matter and excess surface exposure.

Feeding conditions
Such as heating of the forage mix or TMR in the feeding trough, slow feed out from the clamp and large open silage faces, extended time between removal from the clamp and feeding this could include being left in the feeder wagon, unclean clamps and equipment and contaminated feeding equipment.

The effects of mycotoxins on dairy or beef herds

Mycotoxins act within animals by changing nutrient absorption and affecting the metabolism. They can disrupt hormone signals which will have a significant effect on fertility. They will often cause the immune system to become less effective which will leave the animal less resistant to other disease and infection challenges.

Mycotoxins can aggravate or exaggerate some of the more common cow health and production problems. Where feed and forage is stored winter dysentery-like symptoms may come and go as “hot-spots” within the clamp are encountered. Even small amounts of mycotoxins can have a negative impact on the immune system without causing full blown problems but leading to minor health issues.

Dairy cow sat down

Recognising the signs and symptoms of mycotoxins

Mycotoxins can be quite difficult to diagnose. It can often happen when all else seems fine, the diet meets the animals requirements and management is good but performance is not quite where it should be or there are unexplained health issues.

The signs of a mycotoxin challenge can often be quite vague. Here are some of common signs and symptoms:

  • Reduced feed intake – which could also be seen as variable intake from day to day
  • Reduced milk production but not necessarily a sudden drop
  • Scouring or bloody scours without a fever
  • Poorer fertility outcomes with decreased conception rates and even abortions
  • Suppressed immune function – this will lead to more secondary diseases and in extreme cases death

Mycotoxins that affect ruminant animals

The major mycotoxins that affect ruminants are described in this chart:


Source Conditions



Forage and grain.
Wet and humid conditions

Reduced milk yield, feed intake and growth


Forage and cereals.
Wet and humid conditions

Poor fertility and abortion.
Reduced milk yield

T2 - Toxins

Forages and maize (late harvested)
Wet and humid conditions

Reduced antibody and white blood cells.
Increased disease incidence


Forage. Warm and dry conditions

Poor fertility and immune system


Wide range of feedstuffs

Scours, kidney damage
Lowered milk production


Wide range of feedstuffs

Liver damage, nervous system

Solving mycotoxin issues

It is not usually effective to test feedstuffs for mycotoxins as there are so many strains which means it is costly and time consuming. It is much better to include a mycotoxin binder and see if there is a response. If no response within a fortnight then the issue lies elsewhere.

You can overcome a mycotoxin challenge with a specialist binder. ForFarmers offers a Micro Balance Detox which is a combination of specially selected biologically active ingredients which bind, transform and degrade mycotoxins. It is a broad spectrum binder that will remove all types of mycotoxin, even those resistant to standard clay binders. It also contains high levels of anti-oxidants to get the cow’s immune system back up and running after the mycotoxin challenge has gone.

For more information

ForFarmers Account Managers are here to help provide nutritional advice, increase your animal's health and performance and consequently your farm's productivity.

For more information on mycotoxins or our range of Micro Balance products please speak to your local ForFarmers Forage Specialist or send us an online enquiry here