Rapid evaluation of nutritional value of rape straw by near infrared spectroscopy

The experiment aims to establish a near-infrared fast-prediction model which measures the nutrition components of rapeseed straw using near-infrared reflectance spectroscopy (NIRS). 125 rape straw samples were collected from Gansu Province, Qinghai Province and Ningxia Hui Autonomous Region, and then the dry matter (DM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE), coarse ash (Ash), neutral detergent insoluble protein (NDIP), acidic detergent insoluble protein (ADIP), acid detergent lignin (ADL), non-protein nitrogen (NPN) and soluble protein (SP) of the samples were determined. 100 rape straw samples were selected as calibration set to build calibration models. Another 25 samples were used as external validation set to evaluate the NIRS prediction model. The results showed that: 1) the contents of DM, CP, NDF, ADF, EE, Ash, NDIP, ADIP, ADL and NPN in rape straw were 93.62%, 5.85%, 67.22%, 55.40%, 2.57%, 7.66% and 1.04%, 0.63%, 13.58%, 1.70%, respectively. 2) The coefficient of determination for cross-validation (1-VR) and coefficient of determination for calibration of DM, CP, NDF, EE, Ash, NPN and SP were greater than 0.9 and 0.84, respectively, indicating that these NIRS models could be used in routine analysis. 3)The model parameters of DM, CP, NDF, EE, Ash, NPN and SP were Standard MSC 1,4,4,1, Weighted MSC 2,4,4,1, SNV 2,4,4,1, Standard MSC 1,4,4,1, SNV and Detrend 1,4,4,1, Weighted MSC 1,4,4,1, respectively, whereas the model of other nutritional components is not ideal and needs further improvement. In summary, the availability of nutritional composition correction model for rape straw was verified by internal and external validation.