The aim of present experiment was to investigate the buffering capacity of some buffers or alkalizers, their effect on digestion and fermentation of high concentration diets. The concentration of 0, 0.5, 1, 1.5, 2 g in 100 ml from different buffers and alkalizing agents including: sodium bicarbonate, sodium sesquicarbonate, magnesium oxide, magnesium carbonate, sodium bentonite, zeolite and combined buffer (0.75% sodium bicarbonate+ 0.75% sodium sesquicarbonate) was used. The initial pH of the buffer solution, the amount of consumed hydrochloric acid for abrupt changes of pH to 5.2 or below it, and the final pH was registered. The lowest amount of the hydrochloric acid was consumed for solutions containing sodium bentonite, magnesium oxide, magnesium carbonate and control for suddently dropping their pH; and highest amount by sodium sesquicarbonate, combined buffer and sodium bicarbonate, respectively. The zeolite buffer also indicated a proper resistance to pH changes and did not have a significant difference with the combined buffer or sodium bicarbonate buffer. The treatments in gas production were included: control or basal diet without buffer, and amounts of 0.5 to 2% sodium bicarbonate, 0.5 to 2% sodium sesquicarbonate, 0.5% sodium bentonite, 2% magnesium carbonate, 1.5, 2 and 2.5% of zeolite and combined buffer, which were added to basal diet. The highest produced gas was in the sodium sesquicarbonate, sodium bicarbonate, combined buffers and zeolite. Therefore, sodium sesquicarbonate, combined buffers, sodium bicarbonate and zeolite had the best position respectively, which were evaluated as suitable buffers for using in diets containing high concentration ingredients for feeding the ruminant animals.