Introduction:
Forage and feedstuff analysis is an important management tool in the development of a proper feeding program. Knowledge of the quality of a feed helps determine where, when, and how much of a particular feed to use. Evaluating feed quality without an analysis can be extremely misleading.Step 1 - Choose the Feeds to be Tested: The feedstuffs chosen for analysis should form the basis of the ration. This will usually include samples of each different type or cutting of hay, haylage, corn silage, and any other roughages. The nutrient composition of roughages varies greatly from year to year and from farm to farm, making yearly analysis a necessity.
Home raised grains should be tested every 2 years to check nutrient quality compared to expected values. Nutrient composition of feeds such as corn and soybean meal vary significantly, and depend upon variety, weather, and processing conditions. Frequent testing of the energy and protein ingredients in mixed feeds, such as growing or lactating rations, is also necessary.
Step 2 - Collect the Feed Sample:
Accurate feed analysis begins on-farm with proper feed sampling techniques. Collection of a representative feed sample is the most important step in feed analysis. Use these guidelines when collecting feed samples:Hay Samples
: To sample hay properly, a hay core sampler is a necessity. Many feed company representatives, county extension agents, and a few veterinarians have core samplers. Place the hay corer into the middle of the narrow end of square bales, or the rounded side of large round bales, and drill to the center of the bale. When sampling from large round bales, an extender is added to the core sampler so that the bale center can be reached. Proper sampling practices ensure that the sample obtained will include the same proportion of leaves and stems that is present in the entire bale. Sample a minimum of 10-12 bales from different locations in the storage area. Better yet, set aside bales that are to be sampled as the hay is being stored. This will avoid hay being buried under or behind other hay in the storage area, and allow a more representative sample to be collected. Mix the samples together in a clean, dry plastic pail. A two-handful subsample sealed in a plastic bag and well labeled is sufficient for laboratory analysis. Flakes of hay or samples grabbed by hand are not representative samples and analytical results will be inaccurate. Many labs will refuse to accept inappropriate samples.Dry Grains
: Sample dry grains by hand or with a grain probe. Sample from various areas in the storage bin, and mix all subsamples in a clean, dry pail. Remove two handfuls of the combined mixture and place the sample in a clearly labeled plastic bag to be sent to the lab.Silage and High Moisture Grains: Silage and high moisture grain samples are best collected during harvesting. Collect a handful of silage from every third or fourth load and place it in a clean plastic bag. At the end of each day, mix the contents of the plastic bag, take a two-handful subsample and freeze it in a sealed freezer bag. Continue this practice each day of harvesting. When the silo is filled, thaw all the subsamples, and mix them together in a clean, dry plastic pail or bag. Take a two-handful sample and place it in a clearly labeled plastic bag. Remove any air present by squeezing the bag, and then seal it securely. This will help to preserve the moisture content of the sample. A sample collected this way will represent the nutrient composition of the entire silo. Any feed variations that may exist due to field differences, varying stages of maturity, or weather conditions will be reflected in the sample.
If more than one type of haylage or silage is stored in the same silo, use a marker to indicate when the change occurs. There is no value in sampling and testing a silage if it is not known when it is being fed. Egg cartons or polystyrene cups are examples of markers which have been used successfully. Put these materials through the blower in liberal quantities whenever a new type of silage starts filling the silo. Then watch for these markers later when feeding the silage from the silo.
Ensiling changes some nutrient levels, particularly the Acid Detergent Fiber (ADF) content, from those measured in the fresh plant material. The ADF analysis is important because it is used to estimate energy content of roughages. An ADF estimate of fermented forage can be predicted using specialized equations, based on the ADF analysis of the fresh feed prior to ensiling. Labeling the sample as "fresh silage - sampled during ensiling" is therefore necessary to accurately predict the energy content of silage that will be fed.
If it is impossible to collect a silage or high moisture grain sample during harvesting, the next best practice is to sample from the silo itself. Samples should be taken over a 2 day period. Allow the silo unloader to run for several minutes, then grab several handfuls of freshly unloaded material and place them in a clean dry plastic bag. Take samples each time the animals are fed during the 2 days. Mix all the subsamples at the end of the 2 day period and submit a two handful subsample for analysis. For pit or bunk silos, use a hay core sampler equipped with an extender and sample from several different sections across the face. Silage or high moisture grain samples collected from storage will only represent a small portion of the silo or bunk. Analysis of these samples, however, will provide a better estimate of the feed quality than would average book values.
Now that all the samples are properly collected, they are ready to send to the feed laboratory.
Step 3 - Submit the Feed Samples: Once the representative sample is properly collected, the process is not yet complete. Samples must be accurately labeled and described. Feed analysis laboratories require a completed "sample input" form to accompany the samples. The input form information and proper sample identification are extremely important to enable the lab to perform the correct analytical procedures. When submitting hay and/or haylage samples, indicate the type (grass, mixed or legume) and appropriate cutting (i.e. first, second, etc.). Follow these general guidelines to determine the type of hay or haylage being submitted for analysis:
GRASS = < 25% legume (alfalfa, red clover, etc.) in the sample
MIXED = 25-75% legume in the sample
LEGUME = > 75% legume in the sample
Equations, specific for the type of forage, use the Acid Detergent Fiber (ADF) analysis to predict the energy content. Most laboratories use these equations and can provide an estimated energy value, expressed as Total Digestible Nutrients (TDN) and/or Net Energy (NE), for hay, haylage, and corn silage samples. Correctly labeling forage samples ensures the appropriate energy estimating equation will be used. Use of the wrong equation will under or overestimate the energy content of the forage and lead to deficiencies or excesses in the formulated ration.
Clearly label samples treated with a non-protein nitrogen (NPN) additive, such as urea or anhydrous ammonia. These feed samples must be dried differently to preserve the added NPN. If the sample is dried normally (oven dried), the NPN is lost and the resulting crude protein analysis will be inaccurate.
A good policy to follow when submitting samples is to include any and all information that will help the laboratory do the best job possible. A list of available laboratories can be obtained from the Cooperative Extension Service.
Step 4 - Choose the Nutrients to be Analyzed: Choosing the proper nutrients to be analyzed is essential to accurately assess feed quality and provide the information necessary for ration formulation. The major nutrients commonly analyzed in feed samples are described below.
Bibliography:
Martin, N.P. University of Minnesota, Dept. of Animal Science. "Analyzing
Forages for Nutrient Content and Production of Animal Performance."
Nutrient Requirements of Sheep. 6th Revised Edition. National Academy of
Science, National Research Council, Washington, D.C., 1985.