Determination of dry matter and crude protein contents of undried forages by near-infrared reflectance spectroscopy

Near-infrared reflectance spectroscopy (NIRS) was used to predict the dry matter (DM) and crude protein (CP) contents of untreated forage samples. Four hundred forage samples were analysed in reflectance mode. Two mathematical treatments based on the order of derivative of log(1/R), the gap in data points and the numbers of data points used in the first and second smoothings were applied. Predictive equations were developed using modified partial least squares (MPLS) with internal cross-validation. The coefficient of determination of calibration (R(cal)(2)) and the standard error of cross-validation (SECV, in parentheses) for DM were 0.92 (12.4), 0.92 (12.6) and 0.93 (11.7) for the two treatments and log(1/R) respectively on a g kg (1) fresh weight basis. For CP the NIRS calibration statistics yielded R(cal)(2) and SECV (in parentheses) values of 0.85 (19.8), 0.85 (19.5) and 0.87 (18.1) for the two treatments and log(1/R) respectively on a g kg (1) fresh weight basis. It was concluded that NIRS is a suitable method to predict the dry matter and crude protein contents of fresh forage without sample preparation. (C) 2002 Society of Chemical Industry.