On the Effect of Calibration and the Accuracy of NIR Spectroscopy with High Levels of Noise in the Reference Values

In modern forage breeding the use of near-infrared reflectance spectroscopy is becoming more and more common for estimating quality parameters such as In Vitro Dry Matter Digestibility (IVDMD) and protein. In this paper a systematic study of the method is made and compared with the conventional method described by Tilley and Terry (1963). The results show that there is good agreement between the method based on the NIRS technique and the conventional method. However, compared with the conventional method, the NIRS method gives much more stable and repeatable results (STD = 1.24 for the conventional method, but STD = 0.30 for the NIRS-based method). A new calibration was done after some small modifications on the equipment were carried out. The result of the IVDMD calculated by use of the NIRS method after the new calibration gave some bias and a larger standard deviation (STD = 0.40), as compared to results for the original analysis. The results are, however, still much more stable than those for the conventional method.