The aim of the research was evaluation of the influence of nitrogen fertilization dose and of various percentage of components on the content of organic and mineral substances and on the food value of festulolium mixtures with red clover. The study included two factors: percentage of red clover seeds in the mixture (40, 60 and 80%) as well as the level of nitrogen fertilization (0, 60, 120, 180 kg∙ha^-1). It was proved that the mixture with 80% part of legume plant seeds was characterized by the greatest content of total protein and ash constituents as well as by the optimum content of crude fibre. Increase of the percentage of red clover seeds in the mixture positively influenced the content of Ca and the decrease of molar ratio of K : (Ca + Mg), which improved the nutritive value of the feed. Mixtures not fertilized with nitrogen were characterized by greater content of protein and lower content of fibre, and they were better balanced, regarding protein and energy, than fertilized mixtures. Size of the nitrogen dose did not have a significant influence on the feed quality.

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