by Mike Brouk, extension dairy specialist
Collecting a representative silage sample is a difficult task and should involve more than just taking a few handfuls of silage from the face of the pile or the bunker silo. Corn silage and sorghum silages are a mixture of stover and grain. In some cases, small grain silages may also contain grain. This presence of grain in the silage creates some special challenges when obtaining a representative sample.
The best way to obtain a representative sample would be to first deface the amount of silage needed for a daily feeding. In an ideal setting, approximately 12inches of the entire face would be fed each day. The defaced silage should be mixed with a loader or a mixer wagon prior to sampling and feeding.
Once the silage is mixed, take a small scoop and scoop 15-20 samples from around the silage into a clean bucket. When scooping, try to scoop a similar amount with each scoop. Scooping will reduce the loss of finer particles from the samples. Simply grabbing a handful will generally reduce the amount of fine particles and increase the amount of the larger particles of stover. Next, blend the contents of the bucket by hand, rolling, or dumping on a small tarp and repeatedly lifting alternate corners of the tarp to mix the sample. Once the sample is mixed, if not already in a pile on a clean table, dump into a single pile and begin to quarter the sample into equal portions. You want to send about one pound of sample to the lab. So depending on the amount of material you have collected, continue to divide the sample into pie shaped portions until you have one pound of material for the sample being shipped to the lab. Make sure you include all the fine particles in the sample being shipped. An alternative method to dividing the sample into pie shaped portions would be to simply scoop 4-6 amounts into the sample bag until you have a one-pound sample, taking care to include all fines etc. in the sample.
Frequently we are asked how often one should submit samples to the lab. It really depends on the amount of silage you are feeding and the consistency of the silage mass that you created. For smaller feeding operations, once a month sampling is generally adequate as long as the silage is consistent. However, if the composition of the silage is variable, then more frequent sampling would be needed. In larger feeding operations, weekly or twice weekly sampling is recommended. On-farm moisture determination is recommended one to two times each week.
