The aim of the experiment was to investigate the effect of external intervention (mechanical stimulation of rumen mucosa by RF brush devices) on the work of the rumen in high-performance Holstein dairy cows and changes in feed composition ration (TMR) on the amount of milk and its quality, feed intake time and consumption, and pH in rumen. Two mixed feed doses were tested. The RF brush application and the TMR change did not show any significant effect on the monitored indicators. The differences between the dairy cows and between the days of the experiment were more pronounced.