Abstract
In this study, the calibration equations for determining the fermentation quality of sorghum silage extract (135 samples) were investigated. The near infrared (NIR) technique could be used to predict the pH value (R^2=0.84;RPD=2.48), lactic acid content (R^2=0.54;RPD=1.50), total VFA content (R^2=0.90;RPD=3.01), acetic acid+propionic acid (C2+C3) content (R^2=0.85;RPD=2.62), butyric acid+valeric acid+caproic acid (C4-C6) content (R^2=0.63;RPD=1.47) and VBN content (R^2=0.89;RPD=3.00) of sorghum silage extract. These results suggested that the NIR technique could also be used for estimating the pH value, total VFA content, C2+C3 content, and VBN content of sorghum whole crop silage. The accuracies of the calibration equations for the pH value, total VFA content, and C2+C3 content were high for an optical path length of about 4mm, because the corresponding specific wavelengths were narrow and these wavelengths were out of the saturated regions. The accuracy of the calibration equation for the VBN content was high for an optical path length of about 1 mm, because the corresponding specific wavelengths were broad and the saturated regions at this optical path length were small.
