A COMPARISON OF KARL FISCHER TITRATION WITH ALTERNATIVE METHODS FOR THE ANALYSIS OF SILAGE DRY-MATTER CONTENT

Eight methods for determining the dry matter (DM) content of silages w ere compared using a diverse set of 14 silages. The methods were oven drying at 80 degrees C and 100 degrees C, microwave drying, freeze-dry ing, toluene distillation using large or small distillation apparatus, Karl Fischer titration, and chemical saponification. There were signi ficant differences between silages (P<0.001) and methods of analysis ( P<0.001), and a significant silage x method interaction (P<0.001). The Karl Fischer and saponification methods gave higher DM values than th e other methods, and differences between the methods increased with re ducing silage DM. A simple multiplicative model fitted to the data sho wed that most of the silage x method interaction could be attributed t o the volatile content of the silages, and the differences between the methods in the proportion of volatiles retained after DM analysis. In a comparison of sample preparation methods, chopped silages and silag es ground with dry ice gave similar DM values when using the Karl Fisc her and oven drying (80 degrees C) methods. The Karl Fischer method al lows the direct chemical determination of silage water content, and is a simple and rapid procedure well suited to the routine analysis of l arge numbers of silages.