A laboratory evaluation of comfrey (Symphytum officinale L.) as a forage crop for ensilage

A 10 m2 area of comfrey (Symphytum officinale) was chopped and ensiled in duplicate laboratory silos, either unwilted or following a 24 h wilt, to test the hypothesis that the crop might be suitable for ensiling as animal feed. Concentrations of dry matter (DM) averaged 112 and 146 g/kg for the unwilted and wilted crops. Both crops were very difficult to chop due to the mucilaginous nature of the material. The concentrations of water-soluble carbohydrates, ash and N in the crops at ensiling averaged 107.0 and 118.0, 143.0 and 148.5, 32.2 and 34.7 g/kg DM for the unwilted and wilted materials, respectively. Buffering capacity averaged 488 and 472 mE kg/DM for the unwilted and wilted crops at harvest. Mean pH values of the silages were 5.43 and 5.16 for unwilted and wilted materials. The fermentation quality of the silages was poor, with relatively low concentrations of lactic acid and mean concentrations of n-butyric acid of 44.1 and 29.4 g/kg DM in the unwilted and wilted silages, respectively. Concentrations of soluble and ammonia N were, respectively, 708 and 470, and 238 and 179 g/kg total N in the unwilted and wilted silages, indicating extensive proteolysis, particularly in the unwilted crop. Without additive treatment and extensive wilting, the fermentation of comfrey leads to poor quality silage.