Silage makers urged to note pre-harvest conditions that could create mycotoxins threat at feed-out

Grass silage makers are being urged to be more aware of pre-harvest conditions that can lead to a mycotoxins presence in their forage in order to anticipate and avoid potential problems at feed out.

According to Alltech UK's ruminant technical manager David Wilde, moulds present in swards prior to cutting can produce the potentially harmful mycotoxins weeks before grass is ensiled, and will remain a threat long after clamps are sealed.

"Moulds are found in the majority of grasses destined for silage, though will not normally be noticed prior to harvest. They grow under a wide range of conditions and release mycotoxins quite naturally, but certain environmental circumstances can increase the likelihood of mycotoxin production, therefore creating levels that livestock may be unable to deal with when the forage is fed," he says.

"Excessive rainfall, unseasonal frosts, or large temperature swings are all examples of the kind of conditions that can exacerbate the presence of moulds and/or stimulate a greater release of mycotoxins.

"The key point with pre-harvest contamination, however, is that many of the moulds will not survive the ensiling process, but the mycotoxins will. So when it comes to feed-out, there may be no mould present to provide a warning, but the silage will still be contaminated with the toxins."

Mr Wilde believes that greater awareness of the causes and effects of mycotoxins will allow farmers to combat the threat more effectively.

"I have encountered a lot of suspected mycotoxins cases in the past few years and many can be traced back to a pre-harvest event," he says. "In virtually every case extensive losses have occurred in the herds before the problem has been identified. By the time action is taken to nullify the visible effects of the mycotoxins, a lot of damage has already been done. There's no doubt that earlier action in the face of a suspected mycotoxin threat has the potential to save thousands of pounds."

Mr Wilde stresses that good ensiling practice, including the use of an effective inoculant and adequate compaction in the clamp, will certainly reduce the possibility of post harvest moulds and mycotoxins. However, even the best ensiling routine is unlikely to prevent mycotoxins that have originated pre-harvest, so vigilance is currently the best available approach.

Alltech's natural yeast-based feed additive, Mycosorb, is recommended by the company as an effective solution where feeds are suspected to be contaminated with mycotoxins.