The development of near infrared reflectance spectroscopy calibrations forundried grass silage and their transfer to another instrument using multiple and single sample standardisation

This study was undertaken to explore the possibility of developing accurate , robust near infrared (NIR) spectroscopy calibrations for undried grass si lage (a very heterogeneous, high moisture forage) without costly or lengthy pre-treatment of the sample. This was achieved by scanning a large surface area of the sample using a coarse transport cell in conjunction with a Fos s NIRSystems 6500 scanning monochromator, which moves the sample vertically past the light source. Equations were produced for alcohol corrected tolue ne dry matter, pH, N-2, neutral detergent fibre, acid detergent fibre, D-va lue (digestible organic matter in the dry matter) and potential metabolic i ntake with accuracy comparable to finely comminuted undried grass silage. T he second objective of this study was to examine the possibility of transfe rring the undried grass silage calibrations developed on the 6500 spectroph otometer across NIR instruments and cell types. The cloning technique of Sh enk was used to match spectrally the 6500 spectrophotometer and a Foss NIRS ystems 5000 NIR spectrophotometer. Seventy undried grass silage samples, ty pical of the calibration set, were scanned through both instruments using a coarse transport cell and a natural product cell. Cloning was based on (a) 30 samples and (b) one central sample. Standardisation files were produced (using the ISI software) and applied to the spectra of the remaining 40 va lidation samples, scanned on the 5000 spectrophotometer (regarded as the sl ave instrument). These standardised spectra were predicted by the master eq uations developed on the 6500 instrument and the results compared to the co rresponding master validation spectra (n = 40) scanned in the coarse transp ort cell and predicted by the master equations (regarded as the reference v alues). An alternative approach of standardising the master calibration set spectra, to look like they were scanned in a natural product cell and reru nning the calibrations, was also performed and the master natural product s pectra predicted using the new natural product equations and compared to th e reference values. In all instances, this cloning technique proved very su ccessful, clearly indicating that undried grass silage calibrations can be transferred across these NIR instruments with little loss in accuracy of pr ediction.