Improved Method for Determining Dry Matter in Silage

A method for a more accurate determination of dry matter in silage is described in detail.After isolating the moisture from the sample by toluene distillation, the alcohol and the volatile bases and acids in the distillate are determined quantitatively, using in part methods previously developed in this laboratory.The amounts of alcohol, bases, and acids found are added to the determined dry matter.Depending on the prevailing acids in the silage, the simplified, one-acid correction or the more precise multi-acid correction can be used.According to the proportion of alcohol, volatile fatty acids and bases in silage and the extraction time used, the underestimation of dry matter can reach 10%.Paeek and Traeey (11) describe in detail various methods for determining water in plant material and discuss compromises in their accuracy.The two methods most commonly used in work with silage, haylage, and similar fermentation products are oven-drying in a blast of hot air, and distillation using organic solvents being nonmiscible with water and having a boiling point higher than water.Oven-drying at 65 C, as described by Barnett (1), not only renmves most of the water but also some organic matter, as can be distinctly noticed by the nmre or less pleasant aroma associated with drying silage.Drying at this temperature does not renmve the water completely.The amount of hygroscopic water remaining in the plant material, according to our experiments (unpublished data), is 2-2.5% of the dry matter.In general, this is not enough to compensate for the loss of volatile organic matter disappearing with the air stream.The loss is quite variable, depending mainly on the composition of the sample.Forbes (6) used drying in a vacuum oven for 22 hr at 50 C and employed a closed system drawing heated, dry, and CO.~-free air through the sample into a red-hot furnace, where a platinum catalyst oxidized the organic matter into CO._. and water.The water and CO: were trapped quantitatively in concentrated sulfuric acid and flaked sodium hydroxide, resoectively.The increase in weight of sodium hydroxide represented the CO~ from the oxi-Received for publication April 2, 1965. ~A contribution of the Massachusetts Agricultural Experiment Station.