The 5 W's and 1 H of silage sampling

Published 28 August 15

The 5W’s (and 1 H) of silage sampling

As the winter feeding period approaches, it is important to know the quality of the silage in the feed store. Dr Stephen Whelan, AHDB Dairy R&D Manager, explains the who, what, where, when, why and most importantly how of silage sampling.

Who:    It is crucial that the person taking the silage sample follows a technique that allows a representative sample of the feed to be collected, and does so in a safe manner.

What:   Most forages can be analysed these days but you should check with the laboratory that will be doing the analysis.

Where: Samples can be collected by coring down through the clamp for once-off feed budgeting and mineral analysis (Figure 1). However, for more routine analysis, a sample should be collected by coring into the pit face (Figure 2).

When:  Samples should only be collected after six to eight weeks, once fermentation has been completed. These can then be used to establish the requirements for purchased feed and also for assessing the mineral content of the silage. For routine diet formulation, samples should be collected on a monthly basis and on a weekly basis for regular DM testing.

Why:    Regular analysis of silage samples allows more accurate formulation of the diet and ensures nutrients are not undersupplied or wasted. Equally, a once-off mineral analysis can highlight any potential issues that the stock being fed on the forage may face (eg K greater than 15g/kg DM will interfere with Mg and Ca in the animal and so is important for dry cow nutrition). For more information, managing the nutrition of your animals see Section 7 of Feeding +.

How:    This is the most important aspect of the silage sampling process. Research in the US demonstrated that a large component in the variation of the results of silage analysis was due to individual operator sampling technique. This work was presented at the AHDB Silage workshop in March 2015.

When sampling the whole clamp:

  1. Using the sample probe, core down through the depth of silage placing the sample from each core into a clean bucket as you progress through ‘W’ format (Figure 1).
  2. Seal the holes with silage tape as you go along.
  3. Once all cores are collected, mix the samples thoroughly with your hand.
  4. Pour the sample out onto a clean surface and mix again.
  5. Separate the sample into four pieces and take small samples from each pile placing them into a sealable bag. Avoid losing small particles by ensuring your hand is underneath the sample when transferring it to the bag (Figure 3). A sample of approx. 200g is required for analysis but check with your laboratory.
  6. Seal the bag, recording which clamp it came from and the date it was collected. You should also include what type of silage it is, eg first cut grass, maize, etc. and whether or not an additive was used.
  7. Post the sample immediately. Ideally, samples should be sent at the start of the week to ensure analysis gets completed as quickly as possible. A good idea for regular sampling is to conduct the procedure on a Tuesday morning.

silage sampling 1

Figure 1. W format for sampling the whole clamp*

When sampling at the clamp face:

  1. If using a sample probe, take samples across the face of the clamp from nine or ten points in a ‘W’ format (Figure 2)
  2. If using a fork, remove the silage at the clamp face taking the sample from behind this and placing it in a clean bucket. Repeat the procedure following the ‘W’ format across the clamp (Figure 2). Silage at the clamp face will often be drier or wetter than that being actually fed to the animals.
  3. Follow from Step 3 onwards 

silage sampling 2

Figure 2. W Format for sampling at the front of the clamp**

silage sampling 3

Figure 3. Correct method of removing sample by hand, preventing smaller particles from falling out.

*Always sample from the clamp in a safe manner

**Avoid sampling from unstable clamp faces as there is a risk of it collapsing