Prediction performance of portable near infrared reflectance instruments using preprocessed dried, ground forage samples

Forage analysis by near infrared reflectance (NIR) spectroscopy has had many advancements since it began in the 1970s. There have been steady improvements in instrumentation, in computers, and chemometric algorithms for developing calibrations. Thus, making NIR the most used technique to routinely analyze samples for forage producers, plant breeders, animal nutritionists, cattle farmers, and feed companies. This study compared the performance of prediction across three different portable instruments compared to a bench top laboratory NIR instrument, using a wide range of alfalfa and grass preprocessed dried, ground forage samples. Laboratory instrument scans were replicated with a reduced spectral range to match the range of each portable instrument. Alfalfa tended to have better calibration and test-set statistics than the grasses in this study. Portable instruments evaluated did not scan the upper portion of the spectral range (1652 2498 mn), which had some negative impact on forage calibration. The SCiO instrument scanned a very narrow range (740-1070 nm); and, although it had comparable results to the laboratory instrument constrained to same wavelength range, most major peaks related to forage quality traits are outside this range. The expensive bench top laboratory instrument had the best performance as expected, while the very inexpensive SCiO portable instrument had much greater error of prediction to the point that, for most traits, the prediction would not be considered reliable. However, the AuroraNir and the NIR-S-G1 digital light processing portable NIR may provide an alternative to expensive bench top laboratory equipment while still providing sufficiently accurate predictions. Therefore, some portable instruments have the potential to be used for on-farm analysis of wet, coarsely chopped forage, and this option must be evaluated in future studies.

Automated summary

Near infrared reflectance (NIR) spectroscopy has made significant advancements since the 1970s, becoming the most commonly used technique for forage analysis. A study comparing different portable instruments to a laboratory NIR instrument found that alfalfa had better calibration and test-set statistics than grasses. The laboratory instrument performed best, while the SCiO portable instrument had higher error rates, offering potential for on-farm analysis in the future.