Calculating silage losses: what does heating cost you per year?

You fertilised well, the weather played along and ensiling went without a hitch. Even so, your crop is only safe once it is at the feed barrier. Of every tonne of dry matter from grass or maize, part is lost along the way. With a few measurements of your own silage pit, you can work out what that costs.

Where is feed lost in the silage pit?

Feed is lost at three stages:

1. During ensiling, for example if the pit is left open too long or the silage is poorly compacted.
2. During storage. This is often where most is lost: in the pit itself, during fermentation. If air or water gets in, yeasts and moulds become active and the silage heats and spoils.
3. During feeding out, if the silage face is open too long or you feed out too slowly.

The tricky part: you hardly see these losses. The silage doesn't visibly shrink, and you can't read the feed value from the outside. That is why it helps to put a figure on it.

How much feed value does heating cost?

Heating can easily cost an additional 10% of feed value (Silage Safe, brochure 2026, based on Eurofins Agro). According to Wageningen University & Research (WUR), up to 17% of the feed value can be lost through heating. Heating usually starts at the edges, in the top layer and at the silage face: that is where air reaches the silage most easily. Rainwater running in along the wall makes it worse. How to prevent this is explained in preventing heating in silage and keeping rainwater out of your silage.

What do losses cost in a silage pit? A calculation example

We use a silage pit 50 metres long, 10 metres wide and 3 metres high.

1. Volume: in the brochure we use 1,750 m³ of grass silage: the volume of the pit plus a small heap above the walls, because the silage is rounded on top.
2. Dry matter: 1,750 m³ x 230 kg dry matter per m³ = 402,500 kg dry matter.
3. Feed value: at a replacement value of €0.22 per kg dry matter, that is 402,500 x €0.22 = €88,550.
4. Loss: if 10% of that is lost, it costs you €8,855 per year.

These figures are for illustration only and depend on silage quality, feed value and current prices.

How do you calculate the losses in your own silage?

You need four figures. Get your calculator out and fill in your own values.

1. Measure your pit. Length x width x average height gives the volume in m³.
2. Work out the dry matter. Volume x kg dry matter per m³. This density varies from pit to pit: grass or maize, how dry the silage is and how well you compacted it. Your feed adviser or a silage analysis will give you a good figure. In the example we use 230 kg dry matter per m³.
3. Work out the value. Kg dry matter x the price per kg dry matter. Use your own cost price, or what you would pay if you had to buy in the feed. In the example, that is €0.22.
4. Work out the loss. Value x the loss percentage. Use 10% for example (Silage Safe brochure, Eurofins Agro), and also look at what 5% or 15% would mean.

Using a calculator for your feed-out rate as well? Those often work in kilos of fresh silage per m³, so the silage as it comes out of the pit. The 230 kg per m³ in this example is dry matter. You can't use those two figures interchangeably.

If you ensile several times a year in the same pit, for example when adding another cut on top of the existing silage, calculate per layer and add up the amounts.

Setting losses against the cost of covering

Set the loss against what a cover costs you. A Silage Safe system lasts around 10 years, so spread the purchase price over 10 years and compare that annual cost with the feed value you would otherwise lose: €8,855 per year in the example.

The price depends on factors such as the dimensions of your pit, the maximum silage height, the system configuration and transport. Want to know what it costs for your pit? Request a quote.

Henry Molenaar of HyCare dairy farm De Bladelse Hoef in Bladel used to cover his silage pits with soil. Since he started working with Silage Safe: "We're losing a lot less feed value now."

How do you reduce the losses?

The pit itself is often where most is lost, so that is also where there is most to gain:

1. Compact well. The less air in the silage, the less heating.
2. Cover straight away and airtight, with pressure on the edges. How to do this is explained in covering a silage pit.
3. Keep rainwater out of the silage. Water raises the pH and gives bacteria and moulds a chance.
4. Feed out fast enough. At least 1.5 metres per week in winter and at least 2 metres in summer. More on this in the right feed-out rate.