Farmers need to pay closer attention to clamp management to reduce the potential for mycotoxin contamination in the wake of warnings that silage is a major source of contamination.

While there’s potential for silage to become contaminated with several different types of mycotoxin producing moulds, including those originating from the field, particularly high levels of penicillium moulds were found in 2016 silage samples, according to Louise Clarke, south west technical manager at Alltech.

“Silage remains the cheapest option for winter feed, however it’s critical that grass is harvested and ensiled properly, to ensure production of a high-quality feed that presents a low risk of mycotoxin contamination,” adds Miss Clarke.

“Penicillium moulds build up in the clamp if conditions aren’t carefully controlled to ensure an anaerobic environment. They’re associated with the production of several different types of toxins, which are known to significantly impair rumen function resulting in acidosis type symptoms, such as diarrhoea. Subsequently, production drops, most notably yield and butterfat levels.

She added: “While taking precautions at harvest will lower the opportunity for contamination with mycotoxin producing moulds, it’s always advisable to carry out a mycotoxin test once the clamp is opened. Preferably, a sample should be taken from the total mixed ration (TMR), to give an accurate picture of the overall mycotoxin risk."

Commenting on the actual harvesting of silage, Dr Dave Davies of Silage Solutions UK said simple measures, such as improved consolidation and better sealing of the clamp can significantly help reduce the risk of in-storage moulds developing.

He advised rolling grass in the clamp to a target density of 750kg of fresh matter/m3 or 220-250 kg of dry matter/m3.

“A high density can be achieved by layering the forage in the clamp in layers no thicker than 15cm and rolling each layer between loads. This will result in an aerobically stable silage, that shouldn't heat up, therefore reducing the risks of mould growth and mycotoxin formation,” said Dr Davies adding that the clamp should also be properly sealed.

“I would advise using a side sheet, oxygen barrier film and top sheet. Sufficient top weight should then be applied to form a firm seal. The junction between the wall, the top sheet and the ramp, are often problem areas and require particular care."