Sampling Stored Forages
Steven M. Jones, Associate Professor – Livestock
Testing the nutrient value of forage is a valuable tool that can be utilized to balance livestock rations. Guessing the nutrient content of a major feed ingredient such as hay can be costly to livestock producers. To realize the value in hay or other stored forage, we need an analysis. Most livestock producers will need to supplement with some kind of stored forage this winter. High prices for soy bean meal, corn and other commodities further justify the cost of a forage analysis.
Forage test forms can be obtained from your county Extension office. These forms contain complete instructions on how to collect forage samples. Proper collection and identification of a sample is very important. A tool is needed to collect hay samples. The cost for forage analysis is $18 per sample. Considering the cost of grain supplementation this year, the cost of analysis will easily pay for itself by preventing over supplementation. The real value is in correctly balancing diets so that productivity of the herd is maintained or improved, resulting in increased profitability.
Each hay type and cutting should be sampled and analyzed separately. Hay harvested on different dates within a cutting should also be sampled separately. Therefore, it is important that each cutting is stored separately and can be identified with its forage test.
Considering the cost of grain supplementation this year, the cost of analysis will easily pay for itself by preventing oversupplementation.
When sampling forages, one cannot overstress the importance of proper sampling technique. Samples should be representative and selected at random. In summary, sample each lot of forage separately, and make sure the forage can be identified with its analysis when feeding.
1. Core samples are preferred over grab samples. Even with hay that is not weathered, multiple core samples will contain a better distribution of plant material, which will result in a more accurate assessment of nutrient composition. Hay sampling probes are available for use through county Extension offices in Arkansas. Samples should be taken from the end of square bales and from the side of round bales and stacks.
2. To correctly sample a rectangular bale, drive the bit into the end of 15 to 20 bales from a particular lot of hay. Drill to the full depth of the sample tube on loose bales and half depth in tight bales. Mix the cores thoroughly, and send the entire sample to the lab in a sealed plastic bag.
3. Large round bales should be sampled on the rounded side of the bale.
4. Twenty to thirty percent of the bales must be sampled to accurately estimate the nutrient composition of the hay. A demonstration project at the University of Arkansas showed differences of 5 percent TDN when as few as 5 percent of bales were sampled within a single hay lot. A minimum of six individually core-sampled, round bales are necessary to have sufficient sample size for an analysis. Sample size should represent the larger of the two, either 6 bales or 20 percent of the number of bales in a lot.
Upon receiving the results from a forage analysis, the next step is to interpret the results. The results are separated into two columns – AS FED BASIS and DRY MATTER BASIS. When comparing a forage analysis to animal requirements, the values reported under dry matter basis should be used.
The following information is reported when a forage sample is submitted for routine analysis through the University of Arkansas Cooperative Extension Service.
- Moisture – water content of a feed.
- Dry Matter – 100 minus the water content. Used to convert AS FED to DRY MATTER. Example: 8.9 -91.3 x 100 = 9.8.
- Crude Protein – a measure of plant nitrogen multiplied times 6.25.
- Acid Detergent Fiber – a measure of plant cellulose and lignin. Acid detergent fiber is commonly used to estimate digestibility (TDN).
- Neutral Detergent Fiber – a measure of plant hemicellulose, cellulose and lignin. Neutral detergent fiber may also be used to estimate digestibility and is highly correlated with forage intake.
- Total Digestible Nutrients (TDN) – an estimate of the supply of energy. The number for total digestible nutrients is derived from equations developed from feeding trials. Equations commonly utilize acid detergent fiber to estimate TDN but may also include crude protein and/or neutral detergent fiber.
- Net Energy for Lactation – an estimate of the supply of energy commonly used for balancing dairy cow/goat rations.
The time and money spent on forage testing has consistently been shown to be valuable for avoiding costly feeding errors. However, a forage test is of little value if the producer is not willing to interpret the results and make supplemental feeding changes when necessary. Knowing the forage nutrient con tent can save money in the winter feed program. A forage analysis is the only way to accurately balance a ration or mineral program. Lastly, the forage analysis determines forage feeding value so you can compare cost of potential supplements.