Analyzing Your Forage

By Clif Little, Extension Educator, Guernsey County. Published in the OSU Extension BEEF Team newsletter, Issue #562. Forage quality changes with maturity and storage.
calendar icon 26 November 2007
clock icon 6 minute read

A forage test can supply useful information about the nutritive value of hay or pasture. This information can be used to adjust the amount of supplement fed. If forage quality is high, the producer can feed less supplement, resulting in savings. Conversely, if the forage quality is low, diet supplementation can improve animal performance, and increase profits. This article discusses how to take a forage sample and how to interpret the laboratory results.

Taking a forage sample: Forage testing forms can be obtained from many county Extension offices or from the website of the lab you plan to use. Several labs are listed here. 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. Your local Extension office may have a Penn State Forage Sampler or similar device. A hay sampler consists of a long tube with a cutting edge on one end and a shank on the other that can be fastened to an electric drill or hand brace.

To correctly sample a rectangular bale, the bit is driven into the end of 18 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.

Large round bales should be sampled on the rounded side of the bale. Collect a single sample from each of 10 to 12 bales from the same lot, combining the core samples into one sample for analysis. If the outer layer of the round bale is weathered, pull away 1 to 2 inches and sample underneath. Drill to the full depth of the tube.

Your hay should be segregated into lots, each lot representing a fairly uniform population of hay. For example, each hay type and cutting should be sampled and analyzed separately. Hay harvested on different dates within a cutting or even from different fields should also be sampled separately. Therefore, it is important that each cutting is stored separately and can be identified with its forage test. When sampling forages one cannot over stress 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 that the forage can be identified with its analysis when feeding.

Silage can also be analyzed. To sample silage, run the unloader and collect from the feed bunk in 5 to 6 places. Put four handfuls of silage into a plastic bag. Collect samples for two or three days, then mix thoroughly and subsample 1 to 2 pounds. Keep samples in the refrigerator during the collection period and store them in a plastic bag. Seal the bag, attach a completed tag and mail immediately or freeze and mail the frozen sample to the laboratory.

Bagged silage can be sampled by cutting slits along the side of the bag in 5 to 6 places. Collect handfuls and mix in a clean plastic bucket. Mix well and bag in plastic with a tag. Reseal the slit with heavy duty tape.

Silage can also be sampled while it is going into the silo. Collect representative samples from each wagon as it is unloaded and mail immediately or freeze the samples. Take the same number of samples from each wagon and keep them in a container. If the silage lot changes (i.e., a particular hybrid, field, area of the farm), start another container. When all samples have been collected, mix the sample within each container, and collect a random 1 to 2 pound subsample for analysis. Seal in a plastic bag and send to the lab immediately or freeze if they can't be mailed promptly. Fresh silage samples are a good way to plan your feeding program. However, it is a good idea to sample silages when they are being fed and have gone through the fermentation process.

Pastures can be sampled by collecting pasture grass at the height animals are grazing. Collect random grab samples of forage from several locations. Air dry the sample if possible, before sending to the laboratory. This can be done by hanging the forage inside a burlap bag for about a week. Fresh samples should be mailed immediately. There are many reasons to forage test. If you are considering testing your forage, most forage testing labs can provide forage or feed analysis.

Interpreting Lab Test Results: Let's say you have sampled four lots of different hay. Let's take a look at some typical lab results. Table 1 shows samples taken from hay produced on a farm in Guernsey County. These samples were all harvested in mid- to late June.

Now that we have our results, how do we use them and what do they mean? As a hay producer you probably have a similar scenario, several lots of hay, each with a different nutrient composition. Let's go through our report and look at the differences between each nutrient and finally determine how we might use these forages. As we consider the nutrient levels in our hay we should consider the animal's sex, weight, daily gain, stage of production, and environmental conditions.

The analysis of these forages has indicated that only one sample (158) can meet most of the nutrient requirements for our cattle. The three other hay sources will need to be supplemented with a protein source and mineral supplement. Our good quality hay should be used for cows requiring an improvement in body condition or lactating and growing animals.

Analyzing your ration will save you money and help to ensure the nutrient requirements of your cattle are being met. Almost all forages should be provided with access to trace mineralized salt. Hay quality is most affected by maturity. Early harvest and pasture rotation before seed heads appear will greatly improve the quality of your forage. Forage quality can vary significantly and so can the nutrient content of your forage. A forage analysis can help you evaluate the nutritive value of hay when buying and selling hay. Without this analysis is will be difficult to correctly determine your winter supplementation program. For assistance with your forage analysis, contact your local Extension office.

Table 1. Analytical Results on a 100 Percent Dry Matter Basis (Except as Noted)
Feed Code # 158 Alfalfa/Orchardgrass 173 Alfalfa/Grass 225 Orchardgrass 178 Alfalfa/Grass
Dry Matter (DM) 83.3 88.1 88.6 88.6
Crude Protein (CP) 16.9 8.4 7.9 9.6
Crude Protein As Fed 14.1 7.4 7.0 8.5
ADF 45.5 40.7 44.4 41.2
NEM 0.48 0.54 0.50 0.53
NEG 0.19 0.24 0.20 0.24
Phosphorus (P) 0.34 0.26 0.29 0.19
Potassium (K) 3.37 2.26 2.28 1.80
Calcium (Ca) 1.39 0.50 0.29 0.55
Magnesium (Mg) 0.33 0.22 0.23 0.22
Parts per Million
Manganese (Mn) 53 89 110 102
Iron (Fe) 68 39 31 32
Copper (Cu) 10 5 5 5
Zinc (Zn) 26 14 23 19
LH = Lowest/Highest Possible Value Detected by Spectrograph  
K/Ca + Mg 1.96 3.1 4.4 2.34

November 2007

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