The Effects of Strains of Yeasts or Lactobacillus buchneri 40788 on the Fermentation, Production of Volatile Organic Compounds (VOCs), and Aerobic Stability of Corn Silage
Several yeasts and Lactobacillus buchneri 40788 were evaluated for their effects on the fermentation, production of VOCs and aerobic stability of corn silage. Freshly chopped and processed corn plants were treated with a) no additive, b) Saccharomyces cerevisiae -1, c) S. cerevisiae - 2, d) an experimental yeast known to produce acetaldehyde under aerobic conditions, or e) L. buchneri 40788 (LB, 4 x 105 cfu/g of fresh forage). Yeasts were inoculated at 1 x 106 cfu/g of fresh forage. All microbes were from Lallemand Animal Nutrition, Milwaukee, WI. Silos (7.5 L, forage density of 224 kg of DM/m3) were ensiled for 70 and 151 d between 21-23 °C. Five replicates were opened for each treatment at each time point. Silage data were analyzed by analysis of variance as a 2 x 5 factorial arrangement of treatments with main factors of days of ensiling, inoculation and their interaction. Silages were analyzed for numbers of yeasts, fermentation end products, aerobic stability and VOCs (d 151 only). The VOCs were determined by solid phase microextraction (SPME) coupled to non-targeted, comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC´GC-ToFMS). Relative to silage with no additive, treatment with yeasts did not affect any of the measured parameters. In contrast, when compared to all other treatments, treatment with LB resulted in a higher concentration (P < 0.05) of acetic acid (1.58 vs. 0.52 to 0.81% at d 70 and 2.24 vs. 0.94 to 1.22% at d 151) and 1,2 propanediol at both openings, and lowered the concentration (P < 0.05) of ethanol (0.37 vs. 1.18 to 1.52%) after 151 d. The VOC profile of corn silage was markedly altered by LB. Approximately, 25% of the volatile compounds detected in corn silage differed in the LB treated silage (P < 0.0067). Decreases were observed in several ethyl esters of medium chain fatty acids along with increases in various esters of acetic acid. Aerobic stability was numerically greater for LB than other treatments after 70 d of ensiling and statistically greater (P < 0.05, > 450 h) than other treatments (50 to 120 h) after 151 d of ensiling. This is the first study to show that not only does inoculation with LB improve aerobic stability in corn silage, but it has marked effects on VOC compounds.
Keywords: corn silage, volatile organic compounds, Lactobacillus buchneri