A fish oil-contg. mineral-fatty additive was prepd. and used to improve the functional properties of milk fat by increasing the concn. of cis-9, trans-11 linolic and triunsatd. fatty acids in butter. No changes in the content of fatty acids during storage of butter were obsd. Sensory properties of butter made of the milk of cows fed with high-dose of fish oil (3%) were deteriorated.