Studies were performed in two stages on 5 sheep (aged 2-3 years and 45-55 kg body weight) from which samples of rumen content and continuous measurement of pH and temperature were taken by rumen canulae. In the first stage of the experiment the following parameters of rumen fermentation were studied: total gas production, methane and carbon dioxide levels, percentage composition of rumen gases, СО₂:СН₄ ratio, volatile fatty acids (VFA) level, fermentation efficiency and the NGGR factor. In the second stage of the experiment a constant pH and temperature measurement, in the rumen of sheep were conducted. The presented results suggest that our method may be helpful for clinical treatment and scientific investigations.