Effect of Essential Oils of Various Plants as Microbial Modifier to Alter Corn Silage Fermentation and in vitro Methane Production

The aim of present study was to assess the effects of individual various essential plant oils on chemical composition, aerobic stability and fermentation characteristics of corn silage and in vitro rumen fermentation and methane emission using gas production technique. Whole crop corn was harvested and ensiled in laboratory scale tubes (4±0.25 kg) for 45 days. Treatments consisted of either corn silage with no additive (control) or treated with 120 or 240 mg kg^-1 DM of cinnamon (Cinn120 or Cinn240, respectively), thyme (Thy120 or Thy240, respectively), mint (Mint120 or Mint240, respectively), oregano (Oreg120 or Oreg240, respectively) or cumin (Cum120 or Cum240, respectively). Treatments were compared with control using the Dunnett test at (P 0.05). Silages treated with cinnamon essential oil had higher DM content compared with the control (P 0.05). The pH value of Mint240 was significantly lower than the control (P 0.05). A significant reduction in ammonia nitrogen concentration of silages treated with thyme essential oil was observed in comparison to the control (P 0.05). Relative to the control, all of applied additives except of mint essential oil caused a significant improvement in silage aerobic stability (ranging from 44% to 400% increment). At 24 h in vitro rumen post incubation, total produced gas from Oreg240 was diminished significantly (P 0.05) compared with the control (44.23 vs. 48.73 mL 250 mg^-1 DM). When compared to the control, all treated silages except of Mint240 or Oreg120 produced higher methane during 24 h incubation (P 0.05). However, the ratio of methane to total gas was not affected by experimental treatments (P 0.05). In vitro dry matter disappearance of Thy120, Mint240 or Oreg240 increased by 10 percent compared with the control (P 0.05). Moreover, partitioning factor of Oreg240 was higher than the control (P 0.05). Results demonstrated the potential of applied essential oils to improve chemical composition, dry matter degradability and aerobic stability of corn silage.