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  • Writer's pictureKPM Partners

Cutting grass above 8cm prevents the build-up of mycotoxins in silage

Early silage analysis results are confirming that mycotoxin contamination of grass silage will represent a key management challenge on Irish livestock farms over the coming months. But such will not be the case in Germany, a point recently confirmed by one of that country’s leading silage specialists, Dr. Bernd Pieper. He explained:

“The moulds that produce the mycotoxins are in the field. And they attach to the growing grass plants close to the soil surface. In Germany, it is standard practice to leave a grass stubble height of between 6 and 8cm. It’s an approach to silage making that eliminates, for the most part, the threat of mycotoxins at feed-out.”

He added:

“Cutting grass to almost soil level increases the risk of mould contamination. And it also reduces the rate at which grass swards grow back. By leaving 8cm of stubble in the field individual plants have sufficient leaf cover to ensure an immediate growth response after cutting.”

Reducing silage losses at feed out is a priority for German livestock farmers. Spraying potassium sorbate on grass destined for the top layers of a grass silo is a technique now commonly applied by farmers and contractors there to reduce forage wastage within a clamp.

“Potassium sorbate is a natural preservative: it kills moulds,” Pieper added. “It can also be included within a total mixed ration in cases where feed is delivered to the likes of an out farm every second or third day.”

Grass accounts for approximately 50% of the silages made on German dairy farms. Given the fast increasing price of soya, livestock farmers across Germany are now seeking to include as much home-grown protein sources as possible with the rations they feed to cattle.

Alfalfa grows very well in Germany. But it is difficult to ensile. “A very effective way around this problem is to spray a mix of silage inoculant, molasses and formic acid at a combined rate of 6L/t on to the lucerne as it is being picked up in the field,” commented Pieper. “The molasses provides a valuable sugar sources for the bacteria in the inoculant while the formic acid delivers an immediate pH drop.”

He added:

“I strongly recommend the use of molasses in cases where fresh forages have inherently low sugar levels.”

Approximately 14m ha of land are farmed in Germany. Permanent grassland accounts for almost 30% of this area.

Dr. Pieper recently hosted a visit for Irish farming representatives to Germany. He developed the silage inoculant Bio-Sil thirty years ago, which now accounts for 15% of the German additive market. His company, of the same name, is based in the town of Neuruppin, located 80km north of Berlin.

In 2022, approximately 4mt of German silages were made with Bio-Sil. The product, which contains strains of the homofermentative bacterium, Lactobaccilus plantarum, was launched earlier this year in Ireland.

Bio-Sil is mixed with water and then sprayed on to the grass as it is picked up from the field.

One possible issue that can arise when using tap water is the possible presence of Chlorine. “Chlorine, if present at concentrations above 0.2mg/L, can kill the bacteria in Bio-Sil,” confirmed Pieper.

“Freshly collected rain water or water drawn from a bore hole are very suitable alternatives if the chlorine content of tap water is now known. He concluded: “Alternatively, tap water can be treated with a de-chlorinating additive.”


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