THE PREDICTION OF FORAGE MAIZE DIGESTIBILITY BY NEAR-INFRARED REFLECTION SPECTROSCOPY

The possibilities of Near Infrared Reflection Spectroscopy (NIRS) to p redict the organic matter digestibility (OMD) of fresh forage maize we re examined. Cellulase digestibility, corrected to in vivo level, serv ed 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, ba sed on the second derivative of the reflected energy at wavelengths 16 20 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 tha n that of the reference analysis. The best equation, developed for a s imulation of an IA-450 filter-apparatus, had a SEP of 0.74%. Cross-val idation on the calibration set showed the validity of the calibrations for a wide range of digestibility. NIRS-predicted OMD was highly corr elated with the reference OMD, whereas calculated OMD, based on consta nt digestion coefficients for the ears and the stalk+leaves, did not s how any relationship.