Effect of drying method for dry matter determination on losses of fermentation compounds in mixed beet silages

The dry matter (DM) content of silage that encompasses all organic matter content is underestimated when determined by conventional methods due to the evaporation of volatile organic compounds (VOC). In the case of beet silage, the high sugar content in beets can accentuate VOC evaporation; therefore, the objective of this experiment was to study the losses of acetic acid, DL-lactate acid, and ethanol from mixed beet silage samples during freeze-drying or oven-drying to assess their volatilization and the appropriateness of using a correction equation for beet silages. Seven different mixed beet silages were freeze-dried or oven-dried at 50 and 60ºC (24 h), or at 70, 80, and 100ºC (6 h). The DM was measured, and the VOC were determined in the wet and dried samples to calculate corrected DM in two different ways: using an equation based on silage concentration of VOC or by adding the VOC losses directly to the DM obtained. Interactions between the drying method and the type of silage were found ( P < 0.01) for the pH, acetic acid, DL-lactic acid, and ethanol content, as well as for their losses during drying. Significant differences ( P < 0.05) were found for all the silages for all the drying methods between the DM determined and both corrected DM. Thus, it is necessary to consider the drying methodology and the chemical composition of silages to evaluate their true DM and organic matter content. Despite these differences, the evaluated equation for correcting DM in beet silages was acceptable and showed reasonable robustness across various oven-drying temperatures.