FROM THE FARM REPORT: HOW TO SAMPLE & PREPARE SILAGE AND GRAIN FOR LABORATORY ANALYSIS

In my September Farm Report article, I discussed why taking feed samples correctly is one of the most critical steps in building accurate rations and preventing unexpected dips in cow performance. I emphasized that feed values can fluctuate significantly from one day to the next, and while some of this variation reflects true changes in the feed — especially depending on storage method, face management, or where material is removed —sampling errors can add additional variability that makes the feed appear more inconsistent than it really is. The goal is to respond to actual changes in the feed, not to adjust rations based on differences caused by poor sampling technique . Because a single inaccurate sample can misrepresent the real nutrient profile of silage or grain, consistent sampling procedures are essential. In this article I’ll focus on how to properly collect and prepare samples from silage profiles and grains, ensuring that the material you send to the lab truly reflects what your cows are eating.

When sampling silage, safety is the top priority. Because the face of a bunker or pile can shift without warning —and tightly packed silage is difficult to grab by hand — employees should never stand directly in front of it. Use a defacer, rake, or loader to remove a clean layer of silage and place it safely on the ground away from the face. Since the silage face is rarely uniform, samples should represent different areas of the profile, including the upper shoulder, middle section, and lower portion, while avoiding spoiled or moldy material (Figure 1). After pulling down a manageable amount and mixing it with the loader to create a loose, uniform pile, collect about ten small grab samples from different spots. This helps capture variation in particle size and moisture. Farms equipped with a drill corer may also use it to sample compacted silage directly if preferred. Combine all grabs in a clean bucket, mix thoroughly, break apart large pieces, and subsample using the quartering method until a final 500 –700 g (1.1–1.5 lb) portion remains (Figure 2). This final subsample provides enough material for accurate laboratory analysis while still representing the actual average of the silage. For wet forages, allow the sample to air out briefly before bagging to reduce condensation, but avoid heat, which can alter sugars and fermentation acids. Place the sample in a labeled freezer bag, press out excess air, and keep it refrigerated until shipping.

Figure 1. Proper silage sampling locations. Samples should be collected from multiple regions of the face — including the upper shoulder, middle section, and lower portion — to capture variation in particle size and moisture. Spoiled, visibly moldy, or loose material on the ground should be avoided. Handful-sized grabs from each area should be placed into a clean bucket and mixed thoroughly before quartering and subsampling.

Figure 2. Quartering process for silage/grains subsampling. After thoroughly mixing all collected material in a bucket, the sample is spread on a clean surface, divided into four equal sections, and two opposite quarters are discarded. The remaining two quarters are combined, and the process is repeated until a final subsample (500–700 g/1.1-1.5 lb) is obtained.

Sampling grains requires a slightly different approach because variability can occur within storage structures, between loads, and — when dealing with mixed feeds — due to ingredient separation during handling. For individual grain ingredients such as corn meal, soybean meal, or dry shelled corn, a grain probe is the most reliable tool because it collects material from multiple depths, including the center and edges of the bin, where moisture and particle size often differ. If a probe isn’t available, grain can be sampled as it flows during unloading, but grabs must be taken throughout the entire discharge rather than only at the beginning or end. Mixed feeds or purchased concentrates should also be sampled from several points within bags, totes, or augured streams to account for settling and separation of fines. After collection, all grabs should be combined and thoroughly mixed in a clean bucket, then subsampled using the same quartering method used for silage until the desired amount is reached (Figure 2). Avoid areas with visible condensation or crusting unless the specific goal is to evaluate spoilage, as these spots do not represent the feed typically used in the ration.

Once the sample has been collected, mixed, and reduced to the proper size, proper preparation for shipping is essential. Forages should be placed in heavy-duty, airtight freezer bags and immediately refrigerated to prevent further fermentation. If shipping is delayed by more than a day, freezing is recommended to preserve nutrient profiles. Grain samples, which are drier and more stable, can be stored at room temperature but should remain sealed and dry. All bags should be clearly labeled with the date, feed type, sampling location, and any relevant notes to ensure accuracy when the lab receives the sample. Using cold packs during transport for forages helps prevent heat buildup, which can alter moisture, pH, and carbohydrate values.

In conclusion, accurate sampling is the foundation of reliable nutrient analysis. By consistently taking multiple grabs from different locations, thoroughly mixing, and correctly subsampling, farms can dramatically reduce sampling error and ensure that laboratory results reflect the feeds entering the ration. This leads to better nutrition decisions, fewer ration adjustments, improved performance consistency, and a clearer understanding of day-to-day feed variability.

— Daniel de Oliveira

doliveira@whminer.com