During the years 2002–2003 a study on evaluation of nutritive value of silage from bog meadows was carried out. Ensilaged plants were harvested from two bog meadows situated in and near the area of the Biebrza National Park. It was a vegetation of Calthion alliance consisting in 70 % of low sedges (meadow I) and a vegetation of Magnocaricion alliance from flooded meadow composed in 80 % of sedges, mostly Carex gracilis (meadow II). Half of the ensilaged material was inoculated with Polmazym (1 l/t of herbage). For a comparison the herbage from the cultivated meadow composed in 80% of grasses and in 20% of herbs and weeds was ensilaged. At the same time the herbage from the same bog meadows was dried for hay. The nutritive value and quality of produced feeds was determined. The quality of silage prepared from bog meadow herbage varied between years. In 2002 the quality of all silages was very good. No butyric acid was found and the content of lactic acid in FM of sedge silage prepared both with and without Polmazym, was similar to that in silage, made from cultivated meadow sward. In 2003 the quality of some bales was low. The butyric acid and greater quantities of acetic acid, especially in silage made without the Polmazym addition, were stated. Silage prepared from bog meadows vegetation contained significantly more crude protein than hay prepared from the same type of vegetation. Also, the content of crude fat and phosphorus was higher and of crude fibre lower. The nutritive value of feeds was significantly improved by ensilage process. The silage made with addition of Polmazym had a higher nutritive value than control silage (without additives). In both years of study they had a higher content of phosphorus and crude protein in the first year of investigation. Phosphorus content both in the hay and in bog meadow silage was significantly smaller than in the silage from the cultivated meadow.