The difficult weather conditions for silage making means that identifying and mitigating mycotoxin risk in winter feeds is essential as silage becomes the main source of forage in the cow’s diet.

The difficult season for silage making, with warm and wet conditions, both in the field, and in silage pits, has resulted in the increased development of moulds, predisposing winter feeds to a higher probability of some level of mycotoxin burden, particularly within maize silages.

Ruminant technical manager at Trident MicroNutri, Anna Millar said:

“While maize represents a really beneficial winter feed for dairy cows, it is notoriously difficult to keep, as it tends to heat.

“This heating is actually coming from rotting bacteria, eating up nutrients as part of their respiration, and the product of that respiration process is the heat.

“It is important to remember that heating and mycotoxins are separate, you can have both, or one or the other, so testing silages is crucial as a precautionary measure.”

The Irish and UK climate, particularly the warm and wet conditions experienced in recent years, lends itself to a greater development of fusarium moulds, particularly in maize silages.

Mycotoxin risk

Fusarium moulds pose an issue for feeding as they produce deoxynivalenol (DON) and zearalenone (ZON) mycotoxins.

Although these moulds are red in colour, making them relatively easy to spot, they can still be present when not clearly visible to the naked eye, and can present multiple problems to the dairy unit.

“First of all, you have a feed waste issue. If you see the red moulds, you should not put them into the TMR (total mixed ration), so there is straight away a practical waste of feed,” said Millar.

“Secondly, depending on the type, fusarium moulds cause issues with reduced milk production, general health and disruption to fertility,” she added.

According to Millar, zearalenone (ZON) mycotoxins, for example, actually mimic the biological activity of oestrogen, disrupting the cows’ fertility.

Fusarium moulds are also associated with liver and kidney damage, affecting cows’ organ systems, while deoxynivalenol (DON) mycotoxins disrupt the gut and cause issues within the gastrointestinal tract.

This can cause gut wall damage, diarrhoea, and can even result in poor growth rates in growing animals, as the gut is not converting nutrients efficiently.

Clinical signs of mycotoxicosis

If you do have a potential mycotoxin issue or are skeptical about the silage you are feeding even if you can’t see it in the pit, the key is to keep an eye on the cows and their performance.

Millar added that “common signs are reduced milk production, and there are links to increased somatic cell count (SCC) and mastitis, as well as fertility problems and diarrhoea”.

The greatest issue with any toxin is, if absorbed into the cow’s bloodstream, it is a foreign body to the cow. Not only do the toxins potentially result in all of these issues, but the cow also has to use energy to get rid of the toxin.

“It is a toxic substance, so the immune system is fired up, there is an inflammatory response, and that is very costly to nutrients and energy,” said Millar.

“Instead of the cow putting her energy into milk production or fertility for example, she must put her energy into this inflammatory response to get rid of the mycotoxins. It leads to a repartitioning of energy,” she added.

Prevention

The key is to be well prepared by regularly testing winter silages to determine the mycotoxin load, and to help understand the mycotoxin burden in a wide range of feed materials.

If clinical signs of mycotoxicosis are noticed, or if animal performance is not as expected, then the best approach is to feed a mycotoxin binder.

The likes of Ultrasorb R. is a combination of ingredients designed to detoxify and bind the major toxins which affect animal health and performance.

There are preventative measures that can be taken earlier in the process with silage additives.

Millar talked about preventing these mycotoxins from the early stages, “by preserving silage, getting good fermentation and a more stable silage, we can reduce the likelihood of heating, and generally preventing the silage from getting mouldy”.

Millar added that using a silage additive can really help to kickstart the fermentation process in the right direction and will minimise the mycotoxin risk.

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