A comparison of Karl Fischer titration with alternative methods for the analysis of silage dry matter content

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Eight methods for determining the dry matter (DM) content of silages were compared using a diverse set of 14 silages. The methods were oven drying at 80°C and 100°C, microwave drying, freeze‐drying, toluene distillation using large or small distillation apparatus, Karl Fischer titration, and chemical saponification. There were significant differences between silages (P <0.001) and methods of analysis (P <0.001) and a significant silage × method interaction (P <0.001). The Karl Fischer and saponification methods gave higher DM values than the other methods, and differences between the methods increased with reducing silage DM. A simple multiplicative model fitted to the data showed that most of the silage × method interaction could be attributed to 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 silages ground with dry ice gave similar DM values when using the Karl Fischer and oven drying (80°C) methods. The Karl Fischer method allows the direct chemical determination of silage water content, and is a simple and rapid procedure well suited to the routine analysis of large numbers of silages.