NEAR-INFRARED REFLECTANCE ANALYSIS OF THE FERMENTATION CHARACTERISTICS OF SILAGE PREPARED BY CHEMICAL TREATMENT TO PREVENT VOLATILIZATION OF FERMENTATION END-PRODUCTS

In this investigation, silage fermentation characteristics were predicted by near-infrared reflectance (NIR) analysis. Silage was prepared by drying in a microwave oven and milling through a 1 mm sieve. Volatilisation of the fermentation end products was prevented by previous chemical treatment with NaOH (10 moles 1-1) and H2SO4 (5 moles 1-1). Treatment of silage with different amounts of these chemicals showed that treatments associated with pH values of 8.5 and 3.5 were optimal with respect to a minimal loss of total volatile fatty acids (TVFA) and ammonia-nitrogen (ammonia-N), respectively. Silage samples prepared for NIR calibration/validation were all chemically treated to obtain pH values of 8.5 and 3.5 before drying and milling. Prepared silage samples with a pH of 8.5 were used to calibrate a Neotec model 51A NIR spectrophotometer with the reflection data (log 1/R) and the corresponding lactic acid, TVFA, acetic acid and butyric acid values. Silage with a pH of 3.5 was used for calibration with ammonia-N. R2 values for lactic acid, TVFA, acetic acid, butyric acid and ammonia-N, for calibration and prediction (validation), respectively, were: 0.89, 0.93, 0.90. 0.68, 0.95 and 0.85, 0,86, 0.92, 0.65, 0.88. Corresponding standard error values (g kg-1 dry matter) were 17.0, 10.4, 6.7, 4.7. 0.9 and 21.1, 18.7, 6.5, 5.8, 1.5, respectively. It is concluded that silage fermentation characteristics can be predicted with a fair amount of accuracy by NIR analysis if volatilisation of fermentation end products is prevented by conversion to their corresponding salts before drying.