EN
The paper indicates the transformations of fatty acids from the fodder in the rumen, and their impact on milk fat composition in the aspect of health-related properties. Modifications of food doses affect, inter alia, the amount of vaccenic acid isomer absorbed in the duodenum, as well as linolenic and linoleic acids with their isomers. However, the accurate analysis of fat given in fodder is required. Moreover, the pasture systems of dairy cows feeding or indoor green forage supply during the summer is of a greater significance. Lauric and myristic acids should not be given with fodder fats because they reduce yield and health-related value of milk. Besides the dietary factors, it is possible to increase milk health-related properties through increased desaturase content in the mammary gland, as well as the presence of new forms of fatty acids in some vegetable oils obtained by genetic manipulations.