Ruminant methane emissions account for approximately 14.5% of anthropogenic greenhouse gas emissions, underscoring the need for microbiome-targeted mitigation strategies that preserve fermentation efficiency. This in vitro rumen fermentation study evaluated garlic oil (GO; 0.03% v/v), rubber seed oil (RO; 2–6% substrate v/v), and their combination (GORO) on fermentation, methanogenesis, and microbial ecology using 16S rRNA gene sequencing and PICRUSt2 functional predictions (n=5 replicates/treatment). The GO and GORO treatments reduced methane yield by ~50% (3.21–3.66 mL vs. 6.54–7.11 mL in control (CON)/RO; p p p p p = 0.08). Microbial analyses revealed that GO induced alpha diversity loss (Chao1: 865 vs. 1,257 in CON; p Ruminococcus 8.2% vs. 2.1%; Fibrobacter 1.9% vs. 0.45%). For GO, methanogenesis suppression was associated with a 76% decline in Methanobrevibacter (p Selenomonas (p Selenomonas as the top biomarker, and network analysis linked Clostridium to methanogenesis (ρ = 0.85 with CH4; p < 0.001). These findings support the use of phytogenic oils as biotechnological tools to redirect hydrogen toward sustainable pathways while preserving microbial ecosystem stability.
Tilahun et al. (Wed,) studied this question.