In the paper, the profile of fatty acids (FA) was analyzed in milk from cows fed on a TMR system (Total Mixed Ration) during a one year cycle, with regard to the composition of lipids in the forages. Roughages (corn silage and haylage), especially those from the 2009 crops, were a significant source of polyunsaturated FA (PUFA), and the forage-based cow feeding started in autumn. It was found that, compared to other seasons, the fat in milk produced during this particular period contained significantly more monounsaturated FA (MUFA), conjugated linoleic acid (CLA), and linoleic acid. The differences were caused by changes in the content of FA occurring whilst storing forage; for example, it was reported that the content of α-linoleic acid in corn silage decreased from 14.50 to 6.43 g·100 g^-1FA. A valuable advantage of the profile of FA in the milk analyzed was the essentially high amount of health-promoting FA belonging to the odd- and branched-chain FAcids (OBCFA): 4.86 g·100 g^-1FA, as well as to the short- and medium-chained FAcids (SCFA): 15.10·100 g^-1FA.