RUMINAL BUFFERS - TEMPORAL EFFECTS ON BUFFERING CAPACITY AND PH OF RUMINAL FLUID FROM COWS FED A HIGH CONCENTRATE DIET

In vitro characteristics of several buffers and alkalinizing agents co mmonly utilized to reduce ruminal acid load were evaluated. Ruminal fl uid was collected from five cows consuming a diet containing concentra te and sorghum silage in a 68:32 ratio (DM basis). This fluid was incu bated with either NaHCO3, a natural sodium sesquicarbonate, a multiele ment buffer or MgO (7.1 g/L of ruminal fluid), or no buffer for 48 h; flasks were removed and analyzed for pH, buffering capacity, and buffe r value index every 12 h during the 48-h incubation. The buffer value index accounts simultaneously for alterations in pH and buffering capa city. Compared with the unbuffered control, all buffering compounds in creased ruminal fluid buffer value index. However, the buffer value in dex separated these buffering compounds into two categories. The NaHCO 3 and sodium sesquicarbonate exhibited similar buffer value indexes; b oth were markedly higher than those for the multielement buffer and Mg O. Although NaHCO3 and sodium sesquicarbonate each increased both rumi nal fluid pH and buffering capacity sharply, the multielement buffer o nly increased pH and buffering capacity moderately. The increase in bu ffer value index for MgO primarily was due to an increase in pH. Both NaHCO3 and sodium sesquicarbonate were fully active within the first 1 2 h of incubation; activity of multielement buffer and MgO reached a p lateau at 24 h. Compared with the multielement buffer and MgO, NaHCO3 and sodium sesquicarbonate should be more beneficial in preventing sho rt-term postprandial increases in ruminal fluid hydrogen ion concentra tion; because of their slower release rates, the multielement buffer a nd MgO should help stabilize ruminal acidbase status, but efficacy mig ht be reduced because of passage out of the rumen.