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Sampling hay and interpreting results critical for farmers

1/12/2014

In last week's article, the importance of sampling hay for crude protein content and how that could lead to needing less protein supplementation if the hay is of higher quality or protein was discussed. So as Spock would say, it is only logical we now cover how best to collect that hay sample and interpret the results.

In last week's article, the importance of sampling hay for crude protein content and how that could lead to needing less protein supplementation if the hay is of higher quality or protein was discussed. So as Spock would say, it is only logical we now cover how best to collect that hay sample and interpret the results.

The most important thing in forage sampling is to have a representative sample by taking at least 20 core samples from each hay lot. The proper method of sampling depends on the type of forage. This article will address proper sampling for hay only. If silage or haylage also is used in feeding, sampling and testing of silage also would be suggested.

Hay: For rectangular square bales, forage sampling should be done by coring in from the ends. For large round bales, forage samples should be taken from the sides, not the front or back, to get a cross-section of the rolled hay. When sampling hay from bales, it is important to use a core sampler rather than using hands to get a representative forage sample. Take a separate sample from each field and cutting; otherwise, forage quality analysis can give you misleading information. Take at least 20 core samples from each hay lot, composite the samples, mix them thoroughly, and take a sub-sample for analysis. Put the sub-sample into a clean, airtight plastic bag with a label including your name, address, forage type, stage of maturity and date harvested. Check with your local Extension office to see if they have a hay probe for loan. Many do.

Common terms and interpretation of forage quality analysis results:

* Moisture is the water present in the forage and is expressed as percent.

* Dry matter (DM) is the percentage of the forage that is not water. One hundred minus moisture content gives dry matter percentage (i.e., if moisture is 65 percent, then dry matter percentage is 35 percent, 100 - 65 percent = 35 percent).

* Crude protein is the amount of nitrogen in the forage. It is the sum of true protein and non-protein nitrogen. True protein such as microbial protein is used in rumen as the food for rumen microbes. Non-protein nitrogen, such as urea, is used in the small intestine. Since protein has approximately 16 percent nitrogen, crude protein can be obtained by multiplying percent nitrogen by 6.25 (i.e., if nitrogen concentration is 3 percent, the crude protein would be 3 percent N x 6.25 = 18.75 percent).

* Acid detergent fiber (ADF) is the sum of hemicellulose, cellulose and lignin. ADF is used as a predictor of digestibility and energy value, and inversely is related to digestibility (i.e., as the ADF percentage increases, then digestibility and energy value decrease).

* Neutral detergent fiber (NDF) is the sum of hemicellulose and lignin. NDF is a predictor of feed intake potential or gut fill in rumen, and inversely is related to feed intake (i.e., if the NDF is low, then feed intake can be high). In general, forage legumes tend to have lower NDF values than grasses, although it depends on the stage of maturity at harvesting.

* Total digestible nutrients (TDN) directly is related to digestible energy and is the sum of digestible fiber, starch, sugars, protein and fat in the forage. TDN is useful for beef cow rations that are primarily forage.

* Net energy maintenance (NEM) and lactation (NEL): Net energy is the energy concentration in a feed. It can be measured by laborious animal trials or can be predicted using either ADF or NDF. Older, mature forages generally have higher fiber and less energy than younger, succulent forages. Thus older, mature forages have lower net energy values than younger forage plants. Most dairy producers generally use NEL to balance rations for lactating cows while some beef producers use NEM.

* Relative forage value (RFV) is an index used to rank forages based on ADF and NDF values. No unit value is used for RFV. It measures overall feed value of forage, and it is used in hay markets, in particular alfalfa.

* Relative forage quality (RFQ) is a newer index than RFV and is based on intake and TDN. One of the big differences in RFQ compared to RFV is RFQ uses fiber digestibility to estimate intake as well as total digestible nutrients (TDN). This RFQ value can be better and a more accurate predictor than RFV for both warm-season and cool-season forages.

Stacy Campbell is

Ellis County agricultural agent

with Kansas State Research

and Extension.

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