title: Effect of malate on in vitro mixed ruminal microorganism fermentation.
abstract: 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.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Animal and Dairy Science, University of Georgia, Athens 30602-2771, USA.
authors.forename: S A
authors.initials: SA
authors.lastname: Martin
authors.forename: M N
authors.initials: MN
authors.lastname: Streeter
mesh_terms: D000818:Animals; D001421:Bacteria, Anaerobic / Q000187:drug effects / Q000378:metabolism*; D002417:Cattle / Q000378:metabolism / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D005227:Fatty Acids / Q000378:metabolism; D005285:Fermentation / Q000187:drug effects* / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008293:Malates / Q000494:pharmacology*; D008297:Male; D012417:Rumen / Q000378:metabolism / Q000382:microbiology*; D013213:Starch / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D008293:Malates; D013213:Starch