– Chris Teutsch, Associate Extension Professor, Forage Specialist, University of Kentucky
Knowing the nutritional quality of forage and hay is an integral part of a profitable and efficient livestock operation. Accurate estimation of forage quality starts with obtaining a representative sample of the forage to be fed. Proper sampling technique is critical.
Hay is preserved in a number of different packages ranging from the small square bale weighing 40-50 lb to the large square bale weighing more than 1500 lb. In Kentucky, most hay is packaged in large round bales weighing between 500 and 1500 lb. Wrapped bale silage is also gaining popularity and should be sampled in a similar manner to large round hay bales with the exceptions listed below.
Figure 1. Always sample hay in lots. A lot is hay that comes from the same cutting and same field.
Obtaining a Representative Sample
Hay should ALWAYS be sampled in lots (Figure 1). A lot consists of hay made from the same field and cutting. A lot should not represent more than 200 tons of dry matter. In the event that a lot exceeds 200 tons of dry matter, multiple samples should be taken and forage quality results should be averaged to represent the overall lot.
Delay sampling until three to four weeks after baling for hay stored out of the weather. During this period bales undergo the heating or sweating process and forage quality can decline. For hay stored outside, it is best to delay sampling until three to four weeks prior to feeding to account for weathering that occurs after harvest. Remember to allow time for sample shipping and analysis and for making the feeding adjustments needed.
A representative sample will consist of at least 20 cores from 20 bales (one core per bale) resulting in a sample size of approximately one-half pound of hay from each lot. Sample bales at random and not on some predetermined characteristic such as leafiness, color, or weed content.
Use a sampling strategy such as dividing the total number of bales by 20 (number of desired cores) can help to get a representative sample of the hay lot. For example, if a lot consists of 240 large round bales and 20 cores are desired, then every 12th bale should be sampled (240 total bales ÷ 20 samples = 12). If the lot contains less than 20 bales, sample every bale. For stacked hay or truckloads count the number of exposed bale ends (square bales) or sides (round bales), divide by 20, then sample every nth bale end or side. Using the above numbers if there are 240 bale ends on an exposed side, sample every 12th bale. Equally sample each exposed side of the stack. Figure 1. Always sample hay in lots. A lot is hay that comes from the same cutting and same field. Figure 2. Large and small square bales should be samples from the ends to a depth of 15 to 18 inches.
Figure 2. Large and small square bales should be samples from the ends to a depth of 15 to 18 inches.
Figure 3. Round bales should be cored from the side to a depth of 15 to 18 inches.
Core rectangular bales by centering the probe in the end and inserting the probe horizontally into the bale (Figure 2). Sample round bales by drilling or pushing the probe horizontally into center of the rounded side of the bale (Figure 3).
For round bales, remove weathered material from the area to be probed prior to sampling. Weathered material represents refusal and should not be included in the sample. The probe should penetrate the bale at least 15-18 inches for rectangular or round bales.
Figure 4. Always submit the entire sample. Subdividing the sample can result in altered lab results since the fine material segregates from the larger particles. Make sure the bag is clearly labeled with all required information.
After the lot has been sampled, the entire sample should be placed into a labeled plastic bag and sealed (Figure 4). Make sure that the bag is clearly labeled with your farm’s name, a description of the hay lot sampled that will allow you to reference the results back to the hay lot, the type of hay, cutting, and year, and the date it was sampled. The sample should be sent immediately to the lab for analysis. In cases where the sample is not immediately submitted, store the sample in a cool, dry place that is not in direct sunlight. Make sure and complete the sample submission form for the lab that you are using. Do NOT subdivide the sample.
Sampling Baled Silage
Sample baled silage in the same manner as hay. Delay sampling until at least four weeks after harvest to allow complete ensiling. Samples should be placed into labeled plastic bags as previously described. Submit the samples immediately or refrigerate until shipped. Remember to immediately repair holes caused by coring using a UV-resistant tape designed for silage film.
Figure 5. If excessively large samples must be subdivided, always use the quartering technique. Quartering a sample is accomplished by thoroughly mixing the collected cores, pouring the sample onto a clean flat surface, discarding opposite quarters, and recombining the remaining quarters. This is repeated until the desired sample size is obtained.
Using a larger diameter or longer probe or collecting more than 20 cores result in a sample greater than ½ lb. This is not problem in itself and may even be more representative of the hay lot. However, most labs are not set up to handle and grind large sample sizes and will only grind a portion of the sample. The portion of the sample ground may not be representative of the lot. Therefore, AVOID SUBMITTING EXCESSIVELY LARGE SAMPLES FOR ANALYSIS. If a sample must be subdivided, it should be done using a technique called “quartering” (Figure 5). Thoroughly mix the sample and then pour it onto a clean and flat sheet of butcher paper or similar material. Then divide the sample into four equal parts. Discard two opposite quarters. Recombine the two remaining quarters. If the sample size is still too large, then repeat the procedure until the desired sample size is obtained.