Proper sampling - Achieving the most reliable results when analyzing for mycotoxins

Number one, as they are not homogeneously distributed within the lot, mycotoxins tend to accumulate in certain areas known as “hot-spots” (Figure 1), thus staying undetected. Number two, masked mycotoxins are not detectable with conventional methods due to physiochemical modifications that occur within the plant as a defense mechanism. These modifications yield a new compound, different from the original standard, impairing the ability of the analytical method to detect it. Although analysis results will show no (or low) contamination, in reality, there is a high risk of contamination as masked mycotoxins may be reconverted to toxic metabolites in the gastrointestinal tract of the animal.

Figure 1. Inhomogeneous distribution of mycotoxins (dark orange) in grains.
Figure 1. Inhomogeneous distribution of mycotoxins (dark orange) in grains.

Proper sampling and sample preparation are the foundations of quality mycotoxin testing. The main problem of assessing the presence of mycotoxins in feed and raw materials is their uneven distribution in the commodity, especially in whole kernels. Sampling is usually the largest source of error in the mycotoxin analysis and can result in up to 76% of the total uncertainty.

A so-called aggregate sample should be an accumulation of several small incremental samples taken from many different locations throughout the lot (Figure 2).
 

Figure 2. Steps for a successful sampling procedure
Figure 2. Steps for a successful sampling procedure

To gain insight into how to sample properly, we describe some possible scenarios below.

When taking samples during transfer, collect incremental samples of products (100 g) at periodic intervals while the product is transferred from one place to another (Figure 3).

Figure 3. Sampling from a moving stream of product. Collect incremental samples of products (100g) at periodic intervals during transfer.
Figure 3. Sampling from a moving stream of product. Collect incremental samples of products (100g) at periodic intervals during transfer.

When transferring with a loading bucket, collect samples of grain from each bucket being loaded (Figure 4).

Figure 4. Sampling of grains during transfer with a loading bucket. The red x represents the spot where the sample should be taken.
Figure 4. Sampling of grains during transfer with a loading bucket. The red x represents the spot where the sample should be taken.

For collecting incremental samples from a grain heap, take samples from across the entire surface area so that all parts of the lot have an equal chance of selection (Figure 5).

Figure 5. Sampling of grain heaps. Each red x represents a spot where a sample should be collected.
Figure 5. Sampling of grain heaps. Each red x represents a spot where a sample should be collected.

For roughages, the most practical way to take a sample is by hand. If possible, collect samples while the material is in motion. It is also important that all layers are represented equally. For sampling after ensiling, the fermentation should be completed beforehand. 

In the case of fresh roughages, leaves and stems are usually distributed at the edges of the truck. Therefore, take the incremental samples by hand, while the truck is being unloaded.

For bag and bunker silos, collect the incremental samples by puncturing the plastic cover using a sharp cone-shaped sampling device. Evenly distribute holes across the entire surface of the silo (Figure 6). Carefully refill each hole immediately after taking the sample and cover them using a strong tape to prevent possible contamination.
 

Figure 6. The picture shows where to collect the incremental samples when sampling bag silos and bunker silos.
Figure 6. The picture shows where to collect the incremental samples when sampling bag silos and bunker silos.

Due to variations in the distribution of leaves, stems and other materials in silage/straw bales, it is recommended to sample 20 small rectangular bales or 15 large bales. Combine 15-20 incremental samples from each bale to form an aggregate sample (Figure 7).

Figure 7. Each red x indicates a spot where to collect an incremental sample when sampling (a) square and (b) round bales.
Figure 7. Each red x indicates a spot where to collect an incremental sample when sampling (a) square and (b) round bales.

BIOMIN Sampling Guide

If you want to have more detailed information on the sampling procedure for mycotoxin analysis, check out our brand-new BIOMIN Sampling Guide (available on request)!

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