The prediction of forage maize digestibility by near infrared refelection spectroscopy

The possibilities of Near Infrared Reflection Spectroscopy (NIRS) to predict the organic matter digestibility (OMD) of fresh forage maize were examined. Cellulase digestibility, corrected to in vivo level, served as reference method. Calibration was based on 261 samples, varying in OMD from 68.0 to 80.3% and validation occurred on 58 samples (71.7-75.9% OMD). With a scanning IA-500 monochromator the best equation, based on the second derivative of the reflected energy at wavelengths 1620 and 1664 nm, had a standard error of prediction (SEP) of 0.65 The repeatability of the prediction amounted to 0.49% and was smaller than that of the reference analysis. The best equation, developed for a simulation of an IA-450 filter-apparatus, had a SEP of 0.74 Cross-validation on the calibration set showed the validity of the calibrations for a wide range of digestibility. NIRS-predicted OMD was highly correlated with the reference OMD, whereas calculated OMD, based on constant digestion coefficients for the ears and the stalk+leaves, did not show any relationship.