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HomeFarming NewsTo wilt or not to wilt?
Catherina Cunnane
Catherina Cunnane
Catherina Cunnane hails from a sixth-generation drystock and specialised pedigree suckler enterprise in Co. Mayo. She currently holds the positions of editor and general manager at That's Farming, having joined the firm during its start-up phase in 2015.
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To wilt or not to wilt?

In this article, Teagasc drystock specialist, Catherine Egan, discusses making quality silage.

Over the coming weeks, decisions made at farm level will have a huge impact on the quality of silage farmers will feed next winter.

Silage makes up 25-40% of the annual diet on beef and dairy farms – depending on the length of the winter across the county.

Silage quality ranges from 58% to 78% dry matter digestibility (DMD) nationally. On average, quality remains poor at around 65% DMD.

How much and what type

The first step to improving silage quality is to decide how much and what type of silage is needed:

  • For spring calving suckler herds, dry cows will need about 6 bales (1.1 tonne DM) per cow 68 DMD silage with all remaining silage at higher quality (72+);
  • Dairy herds (spring calving) need about 0.8t DM of 68 DMD silage with 100% of the remainder as high quality (72+). At least 50% of total silage will need to be high quality
  • Lastly, calf-to-beef systems need 100% of silage at 72+ DMD.
Grass growth stage

Grass growth this year has been slow to date. The grass growth stage at harvest is the most important factor deciding silage quality.

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Once seed heads appear, DMD will be around 70% at most, and will drop by 1 point every 2-3 days after that.

Lodged crops with dead material at the base will have 3-4% lower DMD still. The primary step to improve average quality is cutting from mid-late May rather than into mid-June

When to cut

Well-managed silage swards closed from late March should have good yields of 5.5 to 6t DM per ha (9-10 tonnes per acre fresh) ready for cutting by late May.

This year yields may be back 7-8%. Using a ‘one big first cut’ approach to make silage will increase the risk of fodder shortages because second cut yields and annual grass production are reduced by pushing first cuts into mid-June.

Given the somewhat slower growth this spring, the advice is to aim for late May with no more than a 4-5 day delay.


A common reason for putting off cutting silage is concern about Nitrogen. A useful guide for fertiliser N is that grass uses 2.5 kg N (2.0 units) per day on average, but this should not be used to decide a cutting date.

If weather conditions are suitable for cutting, test the grass crop for sugars rather than sticking rigidly to the ‘2-unit rule’; you can safely harvest the crop sooner – depending on conditions.

High sugar content allows the crop to ferment quickly in the pit/bale, reducing pH and preserving the crop correctly. Teagasc advisory offices offer a testing service (nitrates also), or, indeed, you can home-test using a refractometer.

If sugars are over 3%, then the crop will ensile readily. While wilting will be beneficial at 2-3%, while below 2%, you will require an additive. If possible, mow in the evening when sugars are highest.


Every year the question of whether to wilt or not arises. Wilting grass to 28-20% dry matter is very beneficial to good preservation – especially if sugars are less than 35 and nitrate is somewhat elevated.

Tedding out for 24 hours is the recommended approach. Grass will not dry enough in large rows even if you leave it for 36 hours.


Work undertaken at Teagasc Grange has shown that farms can lose up to 20% of DM post-ensiling through poor management.

This can be a combination of:

  • Effluent losses;
  • Failure to seal pits fully;
  • Damage to bales.

Seal pits quickly and completely, and regularly monitor for damage by vermin.

Safety at silage time

Silage time is a very busy, pressurised time on farms. It is also an exciting time for younger family members who like to see large machines in operation. This is a dangerous combination.

Keep all non-essential people well away from yards and working fields. Have a traffic plan in place and place warning signs at exits to public roads.

Second cut

With earlier cutting, there is a great opportunity to make a cost-effective second cut of silage in July. Speak to your adviser about a feed budget and proper fertiliser plan for second cut silage.

You can find more farming tips here.

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