Correct Sampling

Why is good sampling important?

Forages are variable by nature. Grass silage is the least variable as it is made up mainly of leaf material of roughly uniform size. Whole crop and maize silages are different as they contain a mix of leaf, stalk and grain in a range of piece and particle sizes.

Collecting a representative sample on farm is vital if the laboratory analysis is to reflect what is actually being fed and to take account of additional variations within a clamp or series of bales.

To help ensure representative samples are taken, the Forage Analytical Assurance Group has produced a recommended procedure for on farm sampling of silage from a clamp. A sample sent to the laboratory should weigh at least 500g.

When to sample – at least six weeks after the silage was made and at regular intervals while feeding out to ensure results relate to the feed being eaten.

Clamp Sampling


Refer to our safe sampling advice for working around or on clamps.

Core samples are best used to give an early assessment of the clamp prior to feeding. - Representative samples should be made by taking 3 full depth (at least 1.5m deep) samples from the top of the clamp along the diagonal of the clamp.

  • The face of the clamp gives a better sample of the silage the animals are actually eating. If there are areas of the face which are mouldy or damaged in any way and this material is not being eaten, then this material should not be sent for laboratory analysis.
  • Samples (from 15 – 23 cm behind the face) should be taken from side to side and top to bottom following a 'W' pattern with a total of 9 - 15 samples taken along the W. Ensure that each sample is at least 250g, taken from a different horizontal and vertical position. Avoid mouldy patches if they are not to be fed to the animals.
  • Samples should be thoroughly mixed together and then reduced to a 500g size before being sent to the laboratory. This is done by by the quartering method outlined below.

Quartering is essential for all silages but particularly so for cereal and maize silages.


Clamp Face

Clamp Sampling

Grass Silage Clamp


Tip the sample onto a clean surface such as a clean board or worktop. Rough concrete is not adequate!!

  • Thoroughly mix the sample to achieve an even distribution of material.
  • If the 2 piles are bigger than the sample size needed, then quarter the material by dividing gain across the pile at right angles to the first separation to give 4 separate piles.
  • Once you have a pile of approximately 0.5 kg in size, carefully place it into a clean plastic bag ensuring ALL the material in this pile is included.
  • Remove as much of the air as possible by squeezing the bag and seal it tightly.
  • Place the sample (min 0.5kg) inside at least 2 plastic bags to prevent dehydration and label clearly with date, type of silage and your reference. Other information such as cut and if additives are used may be helpful for the laboratory.
  • Now it’s important to prevent any changes in the sample before it reaches the laboratory for analysis. To do this, keep cool by storing in a fridge and send to the laboratory as soon as possible. Avoid sending late in the week as the sample could spend the weekend in transit and may deteriorate.

A sample which is well mixed and sent for analysis as quickly as possible will yield the most accurate results of the nutrition of the silage and what is being fed to stock.

Bale Sampling

Follow the same principles as above, taking samples from at least five bales of the same batch.


Silage Bales in Yard

Mixing Sample

Filling Sample Bag

Our Contact Details

Forage Analysis Assurance Group
First Floor, Unit 4 The Forum
Minerva Business Park, Lynch Wood
Peterborough, Cambridgeshire, PE2 6FT
+44 (0)1733-385230

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