Experimentally it was found that: a. milk protein content was more sensitive than milk production to amounts of aminoacids LYZ and MET, b. increasing of milk proteins percentage was independent on milk production, c. caseine was the most influenced milkfraction, d. cows in early lactation responded to LYZ and MET supplement by their milk production more often than ones in late lactation and the reaction was stronger if dry matter NS content was at the desired level, e. with the change of milk protein production the milk fat production often increased, f. protected MET administration in transit period positively affected milk production and health state of high productive dairy cows.