Winter feeding is well underway and many farmers have long opened their silage pit to start using the reserves of grass saved earlier in the year.

But how much silage is available on your farm?

To make it easier for farmers to calculate how much silage they have, Teagasc has developed a guide to calculate the quantity of silage available.

To calculate the amount of silage in a pit, Teagasc says farmers must first measure the length, breath and height of the clamp.

Once measurement is complete, farmers will have the area (m3) of silage available and can then estimate the quantity of fresh-weight silage available (t) using a simple calculation.

This calculation depends on the Dry Matter level of silage, and as a rough guide farmers with very wet silage (DM 18%) need to multiple the area available by 0.81.

For drier silages, farmers will need to multiple the total available area by either 0.77 (DM 20%) or 0.68 (DM 25%).

Calculating how much silage is in your pit
  • Step 1: Measure length, breath and height of your silage pit.
  • Step 2: Multiple the length x breath x height = Total silage area available.
  • Step 3: Estimate the Dry Matter level of your silage.
  • Step 4: Multiple the total available area by either 0.68, 0.77 or 0.81 (depending on silage DM).
  • Step 5: Calculate how long the silage will last the animals on your farm.

Example: Calculating the quantity of silage available

Silage height (3m) x silage width (8m) x silage length (24m) = silage area (576m3)

If the silage has an estimated Dry Matter of 25%, the amount of silage available is: 1,890 x 0.68 = 391.7t.


How long will the silage last?

Teagasc has also set a number of guidelines on the quantity of pit silage different cattle types will eat each month over the winter.

It says that dairy cows will need 1.6t of pit silage each month, so over a four month winter a dairy cow will eat 6.4t of silage.

Therefore, the example pit given above will provide enough silage for 61 cows for four months.

A similar calculation can also be used to calculate how long the silage left in your pit will last suckler cows.

Calculating how long your silage pit will last:
  • Step 1: Calculate the quantity of silage available.
  • Step 2: Identify the animals the silage will be offered to.
  • Step 3: Count the number of animals that require silage.
  • Step 4: Calculate the amount of silage needed each month (type of animal x number of animals).
  • Step 5: Calculate how long will your silage pit will last (available silage/monthly requirement).

Example: How long silage will last a 60 cow suckler herd

If the silage pit on the farm contains 397.1t of silage, a farmer can calculate how long it will last by:

Suckler cow silage requirement (1.4t/month) x Number of cows (60) = Monthly silage requirement (84t).

Once the monthly requirement has been calculated, the farmer will then be able to judge how long it will last by dividing the total available by the monthly requirement.

Total pit silage available (397.1t) / Monthly requirement (84t) = Months of silage left (4.7 months).

Source: Teagasc

Source: Teagasc