Much of the information you need to know when evaluating a forage-testing lab can only be learned by asking, says Don Meyer.
Workers at reputable labs should be willing and able to provide details about their labs' capabilities and procedures, adds Meyer, president of Rock River Laboratory, Inc., Watertown, WI.
“We don't mind those kinds of questions, because no one is questioning our integrity,” he says. “They're questioning how good of a job we can do for them. And we want to give them all the information we can so they can be confident in the results that we give them.”
He told attendees at Hay & Forage Grower's Western Hay Business Conference in Loveland, CO, that lab testing is a valuable tool for evaluating forage quality. But errors are inherent in any analytical procedure, so test results aren't 100% accurate.
Protein tests typically vary 1% within a lab, for example, so a 20%-protein sample may be reported as 19% or 21% protein.
The typical in-lab variation for ADF is 1%, too, and for NDF it's 1.4%. While those differences are small, they have a significant impact on relative feed value (RFV) or relative forage quality (RFQ) scores. Since the RFQ calculation involves more individual analyses than RFV, the reported score is likely to be less accurate, says Meyer.
He suggests that hay sellers state RFV and RFQ as ranges rather than finite numbers.
“If I had hay that tested 162 for relative forage quality, I'd say it was over 150,” he says.
Analyses of individual forage components may vary twice as much between labs as within labs. So he suggests that you identify a reliable lab and use it for all your testing.
First, though, make sure you're collecting representative samples. Sampling errors may be the most common cause of forage-test inaccuracies, says Meyer.
For information on proper sampling techniques, go to the National Forage Testing Association (NFTA) Web site, foragetesting.org, and click on forage sampling.
“If you follow a recommended procedure all the time and are an unbiased sampler, then your sample and your analysis will better represent the stack of hay that you're sampling from,” he says.
He lists four steps for choosing a lab:
Make sure the lab is certified by NFTA. That non-profit corporation sends check samples to labs several times a year, certifying those that report reasonably accurate results.
“It shows that a lab is working to stay current on methodologies, and that it's willing to do what's necessary to show that its results agree with a broad spectrum of labs across the country,” says Meyer.
It should analyze samples for all components instead of reporting book values. Book values can be misleading. For example, the 2001 NRC book value for ash in immature alfalfa is 9.2%. But samples tested at Meyer's lab in 2005 ranged from 1.88% to 21.23% ash.
“Every 1% change in ash will result in a three-point difference in RFQ,” he points out. “So being different from that book value by three or four points can change your RFQ significantly.”
To find out if a lab uses book values, you need to ask.
“That isn't something that labs necessarily want people to know, but it's something that customers really need to ask.”
The lab should have wet chemical backup for data generated by NIR. Wet chemistry is needed to test NIR outliers — samples that don't fit within the lab's set of NIR calibrations. It's also needed to periodically update the calibrations.
Qualified personnel should be available to answer questions.
“I know there are labs out there that basically went out and bought an NIR and set themselves up as a lab,” says Meyer. “But they have no clue as to what went into the calibration of that instrument, or what to do in case they have an outlier. They probably don't have qualified people and probably shouldn't be in this industry.”
Forage-testing labs that have been certified for accuracy by the National Forage Testing Association (NFTA) for 2006 will be announced later this month, says Dee Fogarty, NFTA secretary.
The labs came within an acceptable range of accuracy for dry matter, crude protein, ADF and NDF on six hay tests last year. Four of the dry, ground test samples sent to labs during the year were alfalfa, one was grass and one was corn silage. Labs are required to use their routine testing procedures on those samples.
Labs pay $375 to be evaluated for NIR or wet chemistry testing; $450 for both methods.
For 2005, 104 labs were certified. The labs are listed on the NFTA Web site at foragetesting.org.