Assessment of the Pinus koraiensis cone essential oil on methane production and microbial abundance using in vitro evaluation system

The objective of this study was to evaluate the potential of Pinus koraiensis cone essential oil (PEO) on in vitro fermentation, methane (CH4) production and microbiota quantification in three different in vitro experiments. First, the main active compounds present in PEO were identified and quantified. Subsequently, the in vitro fermentation characteristics and CH4 production after PEO supplementation (0.20 g/L) at different ratios of forage-to-concentrate (F:C, 100:0, 70:30, 50:50, 30:70, and 0:100; Experiment 1) were evaluated. At a F:C ratios of 50:50, control (CON) and PEO supplementation led to similar total volatile fatty acid concentrations, while CH4 production (13.7%) significantly reduced. Based on this result, we determined that 50:50 F:C ratio can serve as an appropriate diet ratio to evaluate dose-response PEO supplementation. The effects of three levels of PEO supplementation (0.20, 0.50, and 1.0 g/L) on CH4 production, fermentation, and microbiota were then determined in vitro (Experiment 2). Methane production decreased (P