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The content of 70 C4-C24 fatty acids (FA) in bulk milk samples of dairy ewes at 4 farms during pasture season and at one farm during winter season was determined by gas chromatography. The FA content in milk fat of grazed ewes was higher up to 4-fold for rumenic acid (CLA), 3-fold for trans-vaccenic acid (TVA) and 2-fold for α-linolenic acid (ALA) compared to that during winter diet. The content of CLA (3.5 %) and TVA (7.9 %) in milk fat of grazed ewes from Tajov farm was higher than that in milk of pasture grazed ewes or cows published previously. Nevertheless, the farm at Trenčianska Teplá because of lower altitude and corresponding climatic conditions in summer showed temporal variation up to 50 % lower content of CLA and TVA. The variations in CLA content during pasture season are primarily related to the seasonal changes of ALA content in pasture plants. These findings suggest that further development of ewes´ milk production should be situated in the northern part of Slovakia at higher altitudes thus providing better quality pastures and more consistent FA composition of ewe milk products with a high content of health affecting FA compounds. Ewe individuality is another important factor significantly affecting the FA milk fat content and also milk yield whereas the ewes´ breed and parity had only little effect. The effect of individuality, breeds and parity of grazed ewes based on FA content was investigated in herd of 148 Tsigai, 124 Improved Valachian and 56 Lacaune ewes grazing pasture and milk samples of individual ewes were taken on the same day. The CLA milk fat content varied up to 5-fold and milk yield up to 12-fold among individual ewes. An inverse relation between the milk yield and CLA content was observed which was not significant though. The ewes with a higher CLA milk fat content and a corresponding higher milk yield were considered in ewe selection for improving milk quality based on the content of health affecting FA compounds. Upon eliminating the data for 25 % ewes with a lower CLA milk fat content and lower milk yield the average CLA milk fat content increased by 10 % while keeping the milk yield.