The concentration of primary and secondary metabolites after 15 years of application of mineral fertilization in the variant with high dose of nutrients (300 kg N.ha(-1) + 32 kg P.ha(-1) + 66 kg K.ha(-1)) and in untreated control was determined in the varied grassland (65% of grasses, 20% of legumes and 15% of other herbs) of dog's-tail (association Festuco-commutatae-Cynosuretum) in the region of Strazovske vrchy (Central Slovakia). It follows from the results that the concentration of primary and secondary metabolites is different and much Varies in different meadow plant species (Fig. 1). The highest concentration of crude protein was found in Taraxacum officinale (24.0 to 26.0% in dry matter) and Trifolium repens (21.60 to 22.80% in dry matter) in both investigated grasslands. Alchemilla vulgaris (16.90 to 17.28% in dry matter) was richest in concentration of soluble saccharides, on the contrary, almost four times lower concentration of soluble saccharides was found in Nardus stricta (4.35 to 4.40% in dry matter). The highest digestibility of organic matter was demonstrated by Taraxacum officinale (82.30 to 83.30%), Alchemilla vulgaris (78.30 to 79.30%) and Trifolium repens,ls (75.30 to 76.10%), in whose dry matter was the lowest content of cellulose and lignocellulose. Nardus stricta is characterized by low value of digestibility coefficients (51.90 to 52.40%), high concentration of cellulose (28.70 to 29.50%), lignocellulose (32.70 to 37.85%), silicon dioxide (2.69 to 2.71%) and esterified phenol carboxyl acids (2.64 to 2.80%).