Silage Advisory Centre

Company technical director John Allen says: “Looking at the results over the last 16 years, the general picture is of declining forage quality.” - see table 1.

“Yet during this time we have seen advances in grass varieties, improved machinery, developments in silage additive effectiveness and a far greater understanding of the processes involved during fermentation.

“Together these mean we should be able to make better silage. The failure to capitalise on these developments is a missed opportunity for the industry.”

“Over the last 16 years we have seen a steady increase in dry matter content, despite some rather wet seasons in recent memory. However, feed value has declined, with lower ‘D’ values, lower ME contents and reduced crude protein percentage.

“Fermentation quality, assessed against a pH target of 4, and volatile fatty acid (VFA) levels, largely of acetic and butyric acids of below 30g per kg, has certainly not improved. Poor and unstable fermentation leads to lower intakes and greater wastage.”

Dr Allen believes the failure to maximise forage quality is costing the industry dear, as average yield from forage per cow has fallen by 24 per cent in the last 10 years - see table 2. But that is the average, and some people are making very good silage each year.

“Looking at the silage results, the difference in ME between the best and worst years is 0.8MJ,” says Dr Allen. “Assuming cows consume 10kgDM per day, this is enough energy for an extra 1.6 litres/cow/day, or 320 extra litres from forage in a typical winter.

“When the best and worst silages each year are compared, the difference in potential yield is consistently four litres per cow per day, or 800 litres over a winter.

Silage costs

“Grass silage is not a cheap crop to make. First-cut costs around £105 per tonne DM, while second cut costs £111 on average. Poorer quality silage is not cheaper to make, so it makes sense to really focus on making a quality product.

“No one sets out to make poor quality silage, and there is a fine balance between sufficient winter stocks, cutting date, contractor availability and weather.

“The top 10 per cent of grass silages are over 30 per cent dry matter, minimum 11.5 ME, well fermented and have good intake characteristics, showing improved silage quality can be achieved.

“The devil, and profit, is in the detail. Focus and dedication to detail will improve the fermentation quality and feed value of silage and produce better yields from forage.”

Top tips for good silage

• Cutting grass at the leafy stage gives the highest D value, which falls as stems lengthen and flower heads emerge
• Cutting date varies with grass mixtures but, as a rule, ME drops 0.1MJ per kg DM each day from the crop bulking up. Cutting too soon increases the risk of high nitrogen levels, which disrupt fermentation.
• Pay attention to preservation and fermentation quality, as this has the biggest impact on silage intakes.
• Ensure the clamp is well sealed and weighted.
• Cut silage to a 20mm chop length with a minimum 30 per cent dry matter. This shorter chop length makes for better compaction in the clamp.
• If using an additive, ensure it is used properly at the correct rate.