Abstract Refusal of antibiotics and a decrease in the greenhouse effect allows active study of the effectiveness of medicinal plants in order to increase the productivity of cattle. The aim of this study was to evaluate the effect of Folia Betulae (FB) and Méntha piperíta (MP) extracts (0.5 ml/kg body weight) on rumenal microbiota and fermentation characteristics against the background of control (C). They were added separately as a substrate to the diets of bulls with rumen fistula (dairy breed, 12-month, diet - 60% hay, 40% barley grain within 10 days). Fermentation parameters (CH4, volatile fatty acids, grain dry matter digestibility (DM) were analyzed daily, and microbiota of archaea and bacteria were analyzed using highly efficient 16S rRNA gene sequencing. FB and MP were prepared by grinding, extraction in a water bath (30 min, 70°C) and filtration. The results of this study showed that the formation of propionate and digestibility of DM did not differ compared to C. Methanobacteria in MP had lower values (P ≤ 0.05) compared with FB and C (less than CH4). Bacterial communities differed: Bacteroidetes predominated more in MP (P ≤ 0.05) and further in FB (P ≤ 0.05) compared with C. At the family level, Prevotellaceae dominated in MP (P ≤ 0.05), Bacteroidales in FB (P ≤ 0.05)) and Porphyromonadaceae in MP and FB (P ≤ 0.05). Firmicutes had lower values (P ≤ 0.05) in all cases compared to C, Clostridia class was lower by 6.0–8.4% (P ≤ 0.05) (due to Clostridiales and Lachnospiraceae families). This study emphasizes the potential use of herbal medicinal substances as a natural feed supplement, which can play a role in reducing methane formation and the development of gram-positive bacteria, without adverse effect to ruminal microbiota. This research was performed with financial support from the RSF (16-16-10048) and project 0761-2019-0005.