The objective of forage sampling is to obtain a feed value estimate of forages that will be fed to livestock. Forages may be sampled as hay or standing pasture. Sampling methods include mechanical coring of bales with a hay probe, pulling hand-grab samples from bales or windrows, pulling hand-grab samples from the standing forage, and clipping standing forage samples. Subsequent analysis will determine feed value for livestock. Accuracy of analysis is largely dependent on sampling method and technique.
There are several methods for sampling baled hay. The best technique is to use a mechanical coring probe made specifically for this purpose. The coring probe consists of a metal tube with a serrated end. The probe is about 18 inches long and 1 inch in diameter, and is attached to a mechanical drilling brace or cordless drill with a special adapter. A wooden plunger is included with probe.
Cores are taken by placing the serrated edge on the side of a hay bale that is most resistant to puncture. This is usually the round side of a round hay bale or the small end of a square bale. By turning the brace and applying pressure, the coring probe cuts through the layers of the hay bale, filling the tube portion of the probe with the sample. After probe has been fully inserted into hay bale, it is then removed by pulling at brace while turning. Contents of the probe, the core, are deposited into a small paper sack or other suitable container by removing the probe from the adapter and pushing a wooden plunger through the probe, thus forcing the coarse hay material out of the probe and into a bag. The process is repeated on additional hay bales until an adequate amount of forage material (6 or more cores per sample) is collected for nutrient analysis. Each container represents a forage sample, and should be identified by a date, cutting, forage type, pasture, and owner. A hay coring probe and drilling brace can be purchased for approximately $150.00, which is relatively inexpensive for anyone serious about producing hay. A coring probe and adapter can be ordered from the Nasco Farm and Ranch catalog by calling 1-800-558-9595 and asking for the Penn State Forage Sampler. Forage sample bags can be acquired from the Soil and Forage Laboratory at the Noble Foundation.
The more traditional method of obtaining forage samples is the hand-grab technique. This method is generally not as accurate as coring and requires a larger sample container. On the other hand, the hand-grab method is faster and does not require special equipment. To sample properly, one must use a consistent technique and select from the middle two-thirds of a round hay bale or the middle third of a square bale. Sample by extending an open hand at least 6 inches into the open side of a hay bale, grabbing a handful of hay, pulling it out of the bale, and placing all of the sample into a container. Do not discard any portion of the sample such as undesirable weeds or grass stems. The forage sample should be as representative of the composition of the hay bales as possible. The process is repeated on several hay bales within the sampling lot. Again, it is important to identify the sample by date, cutting, forage type, pasture, and owner.
The hand-grab method can also be used before baling. This simplifies the procedure, but increases the potential for selective, or biased, sampling to occur. For best results, non-selectively grab a handful of hay from the middle of the windrow immediately in front of the baler. Samples should represent the state in which the hay will be stored in bale form. Sample uniformly across the field. Make collections for each sample at regular intervals (ie, every 30 minutes or every 10 bales). Do not sample more than 30 minutes before baling. The condition of curing hay can change considerably in our environment within a short period of time.
Hay Sampling Procedure
Care should be taken when sampling hay. Samples should be uniformly obtained from several bales (6 bales minimum) throughout each sampling lot. Avoid sampling only one or two areas in the lot. Each sampling lot should be defined by date baled, cutting, forage type, and pasture. The owner's name (or farm name) should also be included on the bag. Indicate if hay was rained on while curing. Any significant event that could cause changes in forage quality would be reason for separation into a separate sampling lot. For a large sampling lot (more than 50 bales), it is advisable to gather several hay samples for analysis.
Sampling Standing Hay
Forage samples can also be obtained from standing or stock-piled forages. The two primary methods are by mechanically clipping and hand-grab sampling. Sampling is usually performed on forages that are to be grazed as standing hay. Hand-grabbing tends to produce a truer measure of livestock nutrient intake than clipping because the hand-grab method more closely mimics the apprehensal, or gathering, abilities of grazing livestock. When clipping, we assume livestock will demonstrate very little selectivity. This is seldom true.
To perform the hand-grab method on standing forage, randomly select a handful of forage and wrap fingers tightly around the upper third portion. Make a swift pull and place the entire sample into the container. Move to another location within the pasture and repeat. Make separate samples where obvious differences in soil and forage structure occur within each pasture. Samples should be evenly distributed across the pasture or area. As time passes and/or forage is removed, forage quality will change. Re-sample standing forage at suitable intervals as long as forage persists.
Standing forage, unlike hay, is not always air dry when sampled. Excessively moist samples need to be dried before shipping. Drying can be achieved by placing paper-bagged sample into a conventional oven set at 150 degrees Fahrenheit until dry. Microwave ovens can also be used for drying standing forage samples. Microwave paper-bagged samples at a 50 to 90 percent power setting until dry.
When forage sampling and testing, the highest degree of accuracy is attained in predominantly monoculture pastures such as bermudagrass or fescue. In stands with a mixed forage composition, such as most native pastures, it is extremely difficult to mimic the grazing selection of livestock by sampling. Thus, standing forage sampling should be limited to monocultures, in most instances. (The exception being for those individuals experienced and extremely familiar with the foraging behavior and selectivity of livestock grazing native range).
All laboratory analyses are performed using wet chemistry. Standard analyses include percent dry matter, percent crude protein, and percent acid detergent fiber (ADF). Percent total digestible nutrients (TDN) is then calculated from percent ADF. Other analyses available on request are nitrate nitrogen and major mineral composition. Due to increased cost associated with non-standard analyses, these should only be requested when truly needed.