Increased mycotoxin risk from silage field aftermath

UK dairy farmers are being advised to remove aftermath from silage fields or run the risk of a higher mycotoxin challenge in the conserved forage they make this year.

“The weather was very mild at the back end of last year and grass was still growing on many farms right through Christmas and beyond. Consequently, there’s a lot of aftermath about, which also means plenty of dead material that’s likely to contain high levels of yeasts and fungi,” says Dr Dave Davies of Silage Solutions.

Dr Davies advises farmers to remove the aftermath if at all possible. “Many dairy farmers don’t like taking sheep on tack, but these grazers really are the best animals for cleaning up the sward in the winter. Essentially, you’ve got two options: either leave the aftermath – which means you run the risk of producing poor quality silage – or remove it, either by mowing it off and wasting it, or bring the sheep in. If neither option is practical, Dr Davies says many farmers will have to focus on excellent clamp management this year.

Mycotoxin management specialist Alltech agrees, pointing out that compaction of grass in the clamp is absolutely crucial. “When clamping silage to reduce the risk of mycotoxin contamination, the aim is to remove as much air from the grass as quickly as possible,” says Lauren Dimmack from Alltech UK.

“Fill the clamp in layers no more than 15cm deep at a time and compact as you go. Your target should be 750 kg of fresh material per m3 (c. 250kg DM). Unfortunately, most farms are only reaching 650 kg per m3 or less, which means too much oxygen is left with the grass, increasing the chance of aerobic spoilage and moulds, and then multiple mycotoxin contamination,” she says.

Dr Davies adds that farmers with a lot of aftermath who are concerned about the risk of aerobic spoilage must use an appropriate silage additive. “Ideally use a homo-fermentative inoculant plus a chemical additive, or a chemical (salt) alone. The inoculant will improve the fermentation and the additional salt reduces aerobic spoilage. This will help stabilise the clamp,” he says.

Other tips to mitigate potential mycotoxin risks when silage making:
Mow grass when it is dry
Aim for a stubble height of 7-10cm
Spread the crop immediately after mowing
Spread the sward to encourage wilting
Don’t leave a thick, dense sward – this is the perfect environment for mould

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