A comparison of different methods for dry matter determination in silages
1974
Larsen, R.E., Department of Animal Science, Faculty of Agriculture, University of Ghana, Legon (Ghana)
The dry matter of 13 silages, including corn and wilted alfalfa-bromegrass silagesand mixtures of the two silages, were determined by six methods, namely: toluene distillation (corrected for total VFA, lactic acid, ethanol and ammonia), toluene distillation (uncorrected), freezedrying, oven-drying at 65°C, oven-drying at 40°C, and moisture-tester drying at lOO°C.Mean dry matter (DM) contents for the six methods were: 40·1 %, 38-7%, 37'9 %, 37·2 %, 37·7 %, and 37·0% respectively. The toluene distillation corrected (TDC) method gave DM values up to 12·8%higher than the oven-drying method. The percentage loss of DM by heat drying depended upon the method and the sample used. The largest differences occurred with silages of low pH, low DM and high concentrations of lactic acid and VFA when heat-dried at lOO°C. Corrections for volumes of total VFA, lactic acid, ethanol and ammonia in the toluene distillate caused significant changes in the DM compared with uncorrected toluene distillation method. TDC method resulted in the highest DM values for all silages and is assumed to be the most accurate of the methods compared. Based on standard error and coefficient of variation, there waslittle difference between the methods, but the greatest precision was obtained with the TDC method. The high variability for all methods would be greatly influenced by the differences in stages of maturity or degree of wilting of silages at harvest.
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