Investigation the buffering capacity of some native alkalizer and buffer compounds and their effect on fermentation and rumen digestion parameters in vitro

Buffering and alkalizing supplements have been used in dairy cows in order to increase production and prevention of ruminal acidosis for many years. Magnesium carbonate is typically obtained from magnesite mines and magnesium oxide is produced by the calcification of magnesium carbonate (reduction, oxidation and burning or heating with extreme heat). Some minerals such as bentonite and zeolite have buffering properties and a special role in the buffering capacity of rumen cation exchange. Buffers raise acetate to propionate ratio and improve fiber digestion. The purpose of this experiment was to evaluate the buffering capacity (BC) and buffering value index (BVI) of some native buffer and alkalizer agents including sodium bentonite, magnesium carbonate, magnesium oxide and sodium bicarbonate and their effects on ruminal fermentation and digestion parameters in vitro.

The first experiment was performed with different types (11 samples) of buffer and alkalizer agents to determine the buffering Capacity (BC) and buffer Value Index (BVI). The experimental samples were including magnesium carbonate A (MgCA), magnesium carbonate B (MgCB), magnesium carbonate C (MgC C), magnesium carbonate D (MgC D), magnesium oxide A (MgOA), magnesium oxide B (MgOB), magnesium oxide C (MgOC), magnesium oxide D (MgOD), sodium bentonite A (SBeA), sodium bentonite B (SBeB) and sodium bicarbonate (SBi). The buffering capacity was defined as the resistance to change in pH from 7 to 5. In order to determine BC, individual samples were dried and ground to pass through 1-mm screen. Buffering capacity was determined by titrating the 30-ml solution under continuous stirring from its initial pH to 5 with 1 N HCl and by titrating a similar prepared solution of samples from its initial pH to 7 with 1 N NaOH. In the second experiment in vitro batch culture technique used. The basal diet contains 80 percent of the concentrate and 20 percent of the forage. half-gram (DM) of base ration with magnesium carbonate (MgC), magnesium oxide (MgO), sodium bentonite (SBe) and sodium bicarbonate (SBi) (1 and 3% DM of ration) were added into the culture vials, then incubated with 50 ml of buffered rumen fluid. Rumen fluid was collected from two ruminally fistulated cows. The gas production was estimated. In vitro dry matter disappearance (IVDMD), pH and ammonia nitrogen (NH3-N) was measured after 8 and 24 h incubation times.

The results showed that the highest pH, buffering capacity and buffering value index were in MgOA and the least of these parameters indicated at MgCD, respectively. Compared to the control lower values were obtained for total gas production (b) of MgO 3%, MgC 3%, MgO 1% and SBe 3% additives. In the present study, addition of MgC and SBi (3% DM diet) also caused a remarkably increase in total gas production. Although the exact mechanisms are not known for the general responses in gas production to supplementation of MgC and SBi, one of the mechanisms of   increasing total gas production is considered to be the higher ruminal microbial numbers caused by the SBi and MgC addition. It has been demonstrated that SBi addition increased the number of ruminal total bacteria, cellulolytic and amylolytic bacteria in buffalo. 3% MgO supplementation increased (P < 0.05) the final pH and it decreased (P < 0.05) the IVDMD compared with the control (after 24h incubation). Significant increase in pH by additive MgO and bentonite can be due to the exchange of cations with hydrogen ion as a modifier of hydrogen ion. Also, in this experiment use of SBe decreased digestibility of dry matter. Some researchers reported that 0.5% MgO (DM diet) does not change the digestibility of dry matter compared to sodium bicarbonate. On the other hand, results of this section of experiment was in agreement with results of gas production, MgC and MgO treatments which had the most and least amount of produced gas (respectively), these also affected digestibility of dry matter. Generally, buffers and alkalizing compounds have no effect on digestibility of dry matter, and probably this reduction in magnesium oxide treatment may indicated a change in the microbial population of ruminal fluid because of the effects of these treatments. In addition, Concentration of NH3-N did not differ (P = 0.2443) between the treatments. Some compounds, such as bentonites, are believed to be able to absorb and release proteins and other nitrogen substrates, so absorbing it when ammonia is high in the rumen, and when the ammonia concentration is reduced, a large amount of it released and thus increases the efficiency of ammonia and protein in the rumen.

In general, the results of this experiment show that magnesium oxide, while increasing the pH of the rumen fluid, also has negative effects on the parameters of gas production, fermentation and possibly microbial activity, and also reduces the in vitro digestibility of dry matter. However, magnesium carbonate and sodium bentonite as a true buffer and due to the preservation and stability of rumen fluid acidity can improve fermentation conditions without having a negative effect on digestibility, so using 1% magnesium carbonate and sodium bentonite as a true buffer is suggested in the livestock diet.