The application of the RMS brushes in the experimental group of dairy cows had no marked effect on the monitored indicators, even in case of change of the feeding ratio. It must be added that both TMRs were deliberately put together so that their parameters were at the threshold of the risk of acidosis. We consider significant only the fact that while the experimental group preserved its rumen pH after the application of RMS brushes at the same level, increasing it slightly after the change of the feeding ratio (by 0.14 pH), the control group without the RMS brushes decreased its pH from the original 5.91 to 5.81. That means that, although the pH of the experimental group was 5.86 and that of the control group was 5.91 in the initial period, the third period experienced the opposite situation: the experimental group had a pH of 6.0 and the control group had a pH of 5.81.