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Silage for success 2023Silage for success 2023

Silage for Success 2023

Farmers are being encouraged to start making plans in earnest for first-cut silage.

It comes after results from over 3,000 forage analyses from Mole Valley Farmers showed last year’s silage was generally of poorer quality. Neutral Detergent Fibre (NDF) was quite high at 48.8%, on average, which means silages – especially later first cuts – were quite stemmy. Meanwhile, lactic acid was low and volatile fatty acids were high at 30%. This results in restricted fermentation and can lower cow intake.

While last year’s challenging weather conditions caught some farmers out, Dr Robin Hawkey, Senior Nutritionist at Mole Valley Farmers, stresses simple steps can be taken to improve silage quality this year.

“Silage is expensive to make regardless but getting it wrong can be very costly. On top of that, there is the grief and stress of the cows not milking well enough. “With the best will in the world, the weather has an impact but failing to plan is planning to fail.”

Below, Dr Hawkey and colleagues discuss how farmers can plan for a good quality first cut.

Carry out a silage analysis

Not only does this tell you what is going on inside the clamp and how it will feed, but it can also help to pinpoint areas for improvement in your silage-making process.

For example, the presence of mould can suggest changes must be made in the sealing of the clamp while low levels of protein can point to crop undernutrition.

Carry out a silage analysisCarry out a silage analysis
Test grass before cuttingTest grass before cutting

Test grass before cutting

Rather than go by traditional dates for cutting grass, farmers should test grass one week before they plan to cut it to make sure it is ready. One of the most important parameters to look at is the level of nitrates in the grass. Excess nitrogen from slurry and fertiliser is a risk because it can depress grass sugars which can cause poor crop fermentation.

Lisa Hambly, head of forage and grassland at Mole Valley Farmers says:

“Having that knowledge will automatically help you to make better silage.”

• Assessing the dry matter of the samples will also help to guide the cutting and wilting strategies.

• Carry out fresh grass tests one week before cutting

• Take representative samples of what you are cutting or sample highest risk fields – those last applied with nitrogen/high levels of slurry

• Sugars need to be high

• Nitrates should be as low as possible

• Results are produced in a simple bar chart with an overall result at the bottom showing if levels are ‘good’ and ‘safe for cutting’ or not

• Ensure you have the right silage additive for the Silage dry matter you will produce and be prepared to change the additive if the dry matter is significantly different than anticipated.

Quality or bulk?

What is needed? Good-quality silage or more of it? This will determine when you cut grass. Dr Hawkey warns:

“If you need bulk you may need to cut later. It is a very simple question, but it needs answering. You cannot ration fresh air.”

He says farmers need to calculate how many tonnes of grass silage they have left over and consider how the ration might differ on the year. He adds:

“Have you got the same acreage of maize as last year and how might that affect how much silage is needed?”

“The ratio of grass to maize silage is also worth considering as it may affect the quality of grass silage needed.”

Quality or bulk?Quality or bulk?


Do not leave grass on the ground for more than 24 hours. Volac silage expert Ken Stroud says:

“ All too often grass is left overnight and brought in at a much higher dry matter and the grass is leaching sugars which affect fermentation.”

“If it is raining, just get it in. It is better to be in the pit at 24% dry matter than left in the field for days.”

Adequate chop length is critical to achieving good clamp consolidation. The target should be 15-25mm with chop length made 4-5mm longer if silage is 25% dry matter or less and shorter if a dry matter of 30% or above is achieved. If there is a high maize silage inclusion in the total mixed ration (TMR), a slightly longer chop might be needed to supply adequate fibre for rumen health, advises Dr Hawkey.

Mr Stroud explains:

“If grass is lush and it is too short it can be more prone to slippage, depending on the clamp dimensions.”

For silage that is 20% dry matter or below, a chop length of 30-35mm or even longer may need to be considered.


Ensile grass in layers 10-15cm deep and use sufficient weight to consolidate the pit.

For every 100t of grass silage entering the clamp, use 25t of machinery (usually two tractors – one with a buck rake and another with a compactor).  Narrow tyres give better compaction than wide ones.

Do not roll each layer for more than 30 minutes, regardless of quality, because this can destroy the structure of the grass.

“If you have dry forage, it is like driving over a cushion and you can force air into the clamp which can create problems with yeasts and moulds. If the silage is coming in at 22% dry matter it needs minimal rolling anyway.”

Grace Burrows, Product Manager at Mole Valley Farmers, says:

“Oxygen is the enemy – it creates higher losses and there is a greater risk of anaerobic spoilage during feed out.”


Clamping top tips

• Clean the clamp before refilling

• Use cling film to achieve a sufficient seal and prevent oxygen from entering

• Use side sheets

• Ensure the clamp is evenly weighted with mats or tyres, for example.

The cost of making poor silage

Lost milk production

2 litres/cow/day at 50p

(2 x 100 = 200 x 180 day housed period x 0.50ppl)

Extra concentrate £30/t extra x 166t £5,000
Extending calving index 10 days at £5/day £5,000
  Total £28,000

Costings are based on a 100 cow farm with a milk price of 50ppl (based on 2022 prices). Silage had a crude protein of 12% and a digestibility value of 61.

Grass & Forage

01769 576232

Feed and Nutritionists

01566 780261


01769 576272