The aim of this study was to estimate the effect of fertilizer UGmax on the energy, protein and mineral value of feed obtained growing cocksfoot grass, perennial ryegrass and meadow fescue. Experiment with cultivation of those plants was established in 2007. To each of rings with a diameter of 36 cm and height of 40 cm, filled with soil material, 8 seeds of one of the studied species were sown. After seed germination, when seedlings achieved the 2-3 leaf stage, negative selection was performed by removing 4 the weakest plants. Next the experimental factors were introduced in the form of the following fertilizing combinations: B1 – soil fertilizer and mineral fertilization, B2 – only mineral fertilization. The experiment was carried out in 2008-2010. Three cuts were harvested each year. In the last two years of the experiment the chemical analysis of yield dry matter was performed. Obtained results were used for calculating the following parameters of energy and protein value: UFL – feed unit for lactation, ULV – feed unit for maintenance and meet production, PDI(N) –protein digested in the intestine plus protein of microorganisms, calculated on the basis of availability in availability of nitrogen from feed in the rumen, PDI(E) –protein digested in the intestine plus protein of microorganisms, calculated on the basis of energy from feed available in the rumen. Moreover, on the basis of macroelement content the Ca : P and K : (Ca + Mg) ratio was determined. Studied species were characterized by a similar content of PDI(E). All species were characterized by the too wide K : (Ca + Mg) ratio; the ratio of calcium to phosphorus was the most favourable in the dry matter of meadow fescue. Soil supply with the fertilizer resulted in an increase in UFL value and content of PDI(N), but it did not contribute to diversifying ULV, PDI(E) and ionic ratios. Supplying soil with microorganisms did not contributed explicitly to improvement of feed value of analysed grasses in individual cuts.

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