Анотация: The aim of the study concerns an estimation of the lipids and their fatty acid composition of the grass associations occupying natural and cultivated pastures at 1200m altitude. Plant samples are taken from the region of the Middle Rhodopes from natural meadows containing mainly Nardus stricta and cultivated meadows predominantly with Fastuca fallax, Lolium perenne L. and Poa pratensis during the period from 15 May to 15 July. The established differences in the molar concentration of SFA, MUFA and PUFA, as well as the changed proportions of the main fatty acids (palmitic, oleic, linoleic and linolenic) are supposed to have influence on the milk fat in the ruminant animals