How ‘Identical’ Samples Were Created

Alfalfa hay samples sent to 16 forage-analysis laboratories last fall as a blind test were prepared by Dan Undersander, University of Wisconsin extension forage specialist.

Undersander received three bales of alfalfa hay from a National Hay Association (NHA) member and took samples, making them look like hay core samples. He then had the samples scanned unground by near infrared (NIR) for forage quality so he had something to compare lab results to.

The unground samples were then sent to NHA members to submit to labs they commonly use. Each lab received and tested three blind samples. Once the growers had the results, they requested the samples back from labs. Results and samples were then sent to Undersander.

Bruce Anderson, University of Nebraska extension forage specialist, gathered and submitted blind samples in much the same way with help from Nebraska Alfalfa Marketing Association members. But his samples weren’t scanned. He thoroughly mixed and subdivided samples.

“To insure that the samples were identical, we tested our separation procedure. We took four other samples and mixed them thoroughly in the exact same manner and subdivided them in the same manner. Then we had all four analyses done in the same lab. We got very good agreement among the subsamples. The average deviation of the sam- ples was less than 2.5 points of RFV,” he says.

At least six samples were sent by N.A.M.A. members and customers to each of 10 labs that they use. Results and samples were returned to grow- ers who sent them on to Anderson to evaluate. Anderson and Undersander then compared variability within and among labs.

Both were asked why fewer than a fourth of the 107 labs certified by NFTA were checked. “It’s simply a matter of time and finances as to how much we could do,” says Anderson.

“Blind tests like this are a lot of effort,” Undersander adds. “Even if we continue to do this, it will always be a random sampling of labs rather than all labs because of the costs. NFTA paid thousands of dollars in lab fees and spent a lot in labor to get the samples sent out to somebody from the region that a lab would normally receive samples.”

How NFTA’s Check Program Works

Six times a year, the National Forage Testing Association sends recognizable check samples to forage-analysis labs that want to receive or retain NFTA certification status. Currently, NFTA sends ground samples to labs, then compares the results. Its purpose is to help labs evaluate their testing procedures and, by doing so, reduce variability within and among labs, says NFTA president Don Meyer.

“But everyone is aware that it’s a check sample from NFTA and labs may treat that sample a little differently than they would a normal sample coming in,” says Meyer, also president of Rock River Lab.

Test results from each lab are graded based on a narrow fixed standard deviation. Labs with tests that are off that standard deviation can earn B or C grades and still be considered certified by NFTA. Labs that get A grades are within that deviation. Any lab that gets a grade lower than a C is not certified. Those grades have not been made public, Meyer says, but customers can request lab grades from labs they are using.

For a listing of NFTA-certified labs, visit: www.foragetesting.org

Please Comment!