Twenty-eight Black-and-White cows were allotted to 7 groups of 4 each and fed for 8 weeks basal ration containing maize, lucerne and beet pulp silage, wet brewer’s grains and meadow hay and different concentrate mixtures without additives (control group) or supplemented with: 10% linseed (Omega, Linola or Opal cv.), rape seed (Spencer or Contact cv.), or 4% fish oil as fat sources in the respective experimental groups. Each ingredient of basal diet and concentrates were given separately. Cows fed diets enriched with vegetable oils produced more milk containing a somewhat lower level of fat, protein and lactose than control cows. Omega or Opal cv. linseeds resulted in an increase in n-3 PUFA, but Linola cv. linseed raised the n-6 PUFA proportion in milk fat. Feeding diets supplemented with fat resulted in a decrease of SFA and increase of the CLA proportion in milk fat, particularly when feeding fish oil.