The analysis encompassed 60 sows of the Polish Landrace and Puławska breeds kept at a pig–fattening farm of the Agricultural University Experimental Unit for Animal Husbandry in Czesławice. The experiment material was divided into 3 equal numbered groups: I (full portion mix containing 20.45 g of raw fat), II (29.83 g of raw fat), III (39.21 g of raw fat). Milk samples were taken on the 7 and 21 days of a natural lactation. The test defined the percentile content of the main milk composition elements of sows: fat, protein and lactose as well as the composition of selected fatty acids in the lipid milk fraction. The chemical milk composition analysis showed that milk of group II and III sows was characterized by a higher percentage of fat content as compared with group I. The differences in its level in both analyzed days of lactation were smaller in groups receiving feed mixes with a greater amount of raw fat. Unsaturated fatty acids (UFA) constituted the largest composition participation in the milk’ s lipid fraction both on the 7 as well as 21 days of analyzed lactations. The highest level of UFA was noted in group III. A slightly lower amount of unsaturated fatty acids characterized the milk of sows in group II. Also the UFA/SFA proportions verifying the milk’ s fat digestion were more favorable in groups II and III.