Effect of malate on in vitro mixed ruminal microoganism fermentation
1995
Martin, S.A. | Streeter, M.N.
The objective of this study was to evaluate the effects of different concentrations of DL-malate (disodium salt) on the in vitro mixed ruminal microorganism fermentation of soluble starch or cracked corn. Ruminal fluid was collected from a steer fed 6.8 kg of forage and 2.3 kg of concentrate supplement once daily, and mixed ruminal microorganisms were incubated in anaerobic media (40 mL) that contained 20% (vol/vol) ruminal fluid in batch culture for 24 h at 39 degrees C. Malate was added to the incubation bottles (n = 4) to achieve final concentrations of 0, 4, 8, and 12 mM. When mixed ruminal microorganisms were incubated with only DL-malate as the substrate, final pH numerically increased, propionate and total VFA concentrations increased (P < .05), and the acetate:propionate ratio decreased (P < .05) as the concentration of DL-malate increased from 0 to 12 mM. Fermentation of cracked corn in the presence of 8 or 12 mM DL-malate resulted in an increase (P < .05) in final pH and propionate concentration. Total VFA tended to increase (P < .21), whereas final concentrations of L-lactate numerically decreased. In the case of soluble starch, 8 and 12 mM DL-malate caused a decrease (P < .05) in methane concentration. When only ruminal fluid (no added anaerobic medium) was used as the inoculum rather than 20% ruminal fluid medium, similar results for final pH, propionate, L-lactate, and total VFA were observed for soluble starch and corn incubations treated with DL-malate. In conclusion, these results show that DL-malate stimulated the in vitro mixed ruminal microorganism fermentation by increasing concentrations of propionate and total VFA as well as final pH.
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