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Frequently, concerns about laboratory testing focus on the methods used in determining forage quality. However, the focus of concern should be on the accuracy of results and not the technique of obtaining the results. To help you determine if the test results are accurate or not, we have outlined below some questions to ask the laboratory manager.
Keep in mind that laboratory monitoring practices increase the cost of the analysis. Asking these 6 questions will help evaluate a laboratory and is one way to become more knowledgeable about purchasing analytical services. Laboratories generally report results of analyses as a single number. This does not mean that hay which tested at 20% CP is exactly 20.0% CP. Instead, it means that the hay is 20.0% crude protein plus or minus some variation. The amount of this variation will differ from lab to lab and from method to method. A variation of about 3% can be expected between labs for measurements of crude protein. In other words, a hay sample which tested 20% CP at one lab would be expected to test anywhere from 19.4 to 20.6% CP at another lab or at the same lab if the analysis was repeated. Variation is usually much higher for fiber measurements than for crude protein measurements.
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