For many livestock farmers, harvesting first-cut silage will be the main priority over the next fortnight.

Heavy and frequent rain showers throughout May have created a backlog of work for silage contractors to get through.

Where cutting has been delayed, forage quality will be starting to decline, as grass heads out and swards with heavy covers begin to lie flat.

Given the rise in inputs and contractor costs associated with silage making, as well as the prospect of rations exceeding £400/t this winter, aim to get silage harvested as soon as weather conditions permit.

Once grass starts heading out, D-value will be dropping by 0.5% unit/day, so delaying by one week will lower D-value by close on 4%.

Every 4% drop in D-value will roughly require an additional 1kg of concentrate to make up the loss in feed value and maintain animal performance.

On 50 finishing cattle, feeding an additional 1kg (£400/t) for 90 days will cost an additional £1,800 this winter. When it comes to harvesting first-cut, outlined are some tips to consider.

Striking the balance between yield and quality

Higher fertiliser and contractor costs mean there will be more farmers looking to maximise grass yields in first-cut, thereby reducing or even eliminating the need for a second cut.

However, there is a balancing point between yield and quality. Once grass starts heading out, it is time to think about harvesting.

Check the base of the sward. If the bottom of the sward is turning white with dead grass accumulating, there is no point delaying cutting beyond this stage.

Grass yields are unlikely to bulk out much more beyond this point, as the sward is starting to die back.

As dead matter accumulates at the sward base, this material will lower silage quality and increase the amount of mould on ensiled grass.

Keep in mind that as grass matures out, there are less grass sugars present to drive fermentation. So, while there may be a higher yield lifted in the field, there will be more waste in the pit and after fodder is fed out.

Finally, delaying cutting date simply to increase yield has a negative effect on regrowth. This is crucial where surplus grazing has been closed for silage.

Heavy yields leave a white aftermath, slowing regrowth and creating a possible grazing shortage. Second-cut will also be late by delaying first-cut.

When to mow grass?

Assume grass will use two units of nitrogen per day from sowing until cutting. If 100 units/ac of nitrogen is applied for first-cut, grass will be safe to cut after 50 days of growth.

Grass can be cut a few days earlier if it can be rapidly wilted to around 30% dry matter and ensiled dry. Mow grass in late morning or early afternoon when sugars are at their peak.

Wilting and tedding

Most farmers report that silage swards are heavy and big crops are expected. After so much rain in recent weeks, grass will be wet and need wilting for at least 24 hours to increase dry matter.

Open the mower out fully to spread the crop as wide as possible. Tedding out grass takes time and comes at a cost, but improves the wilt in a heavy crop and reduces the amount of waste in the pit.

Cutting residual

Mature grass will have a high percentage of stem present, which is ultimately fibre and has little feed value.

Don’t set the mower tight to the ground. Leave a 3cm to 4cm residual behind. If soils are on the wet side, cutting too low runs the risk of contaminating grass with soil.

This risk is further increased when raking up multiple swathes for the harvester or baler. A slightly higher residual will keep cut grass up off the soil, reducing contamination and helping speed up regrowth.

Chop length for grass

Keep chop length in mind when harvesting. Grass that is too long is hard to buckrake. Cattle also have a tendency to drag longer chop silage back in to pens when exiting the feed face.

Grass that is too short also causes ensiling problems, as well as rumen issues. For silage around 30% dry matter, aim for a chop length around 8cm to 10cm, roughly the width of a cow’s muzzle.

Filling the clamp

Filling the clamp is the most important stage of silage harvesting. Having the right person on the buckrake can make a big difference to how well grass ferments.

Fill the pit in even layers around 12cm to 15cm deep. Keep the angle of the grass ramp below 20° to compact and consolidate fodder properly, making the clamp more stable.

Cover the pit ASAP

Grass will start heating once ensiled, so it is important to finishing rolling and cover the clamp as quickly as possible.

Covering the pit will create an anaerobic environment, which aids grass fermentation. The earlier this is done, the better. Apply plenty of weight on the top sheet and along the side walls.

Using plastic sheets along the side walls will help reduce waste along the shoulders of the pit. The sheets should fold in at least three to four metres on top of the clamp.

Wrapping and stacking bales

With bales, wrap as soon as possible. This stops bales sagging and going out of shape. Apply at least six layers of plastic to improve fermentation and reduce waste.

Wrap is more expensive this year, up about £25/roll, which works out around £1/bale. But skimping on plastic should be avoided at all cost.

Bales should also be stacked as soon as possible, preferably on a hardcore area in the yard. Stack bales on their end to reduce stacking.

How high bales can be stacked will vary. High dry matter bales packed tightly can support more weight than bales of leafy, surplus grass.

Mark a few stacked bales from different fields with spray paint, making it easy to target silage for specific cattle groups during winter.

Slurry and nitrogen for second cut

Once silage has been harvested, slurry should be applied at the earliest opportunity to replace nutrient offtake and encourage regrowth. Chemical nitrogen should then be applied around one week to 10 days after slurry is applied.

Farm safety

Keep farm safety is mind at all stages of silage harvesting. Young children should not be in the yard when trailers are moving in and out to unload.

Make sure all machinery is in proper working order and have all guards present. You might know of a potential problem with a machine, but a family member or neighbour helping out might not.

Read more

Five tips for managing cows through the breeding season

Watch or listen: Farm Tech Talk - The Livestock Show