Automatic continuous measurement using various sensors can be used to take measures in real time to improve productivity and welfare of dairy cows. The activity of the sensors for measuring the time of eating and rumination was verifi ed in 36 dairy cows. Dairy cows were divided into 2 groups. Each group was fed mixed feed ration (TMR) with a different crude fibre content in the fi rst 21-day period. After 21 days, the TMRs were replaced. In dairy cows fed experimental TMR with a higher content of crude fi bre (TMR-P), signifi cantly (P < 0.05) longer eating and rumination time was recorded than in dairy cows fed control TMR (TMR-K). In dairy cows fed TMR-P, a higher fat content.