## 4 Discussion
### Production of Methane and Carbon Dioxide  
In our study, we examined the significant effects of various doses of SAG, PIN, and CLO on the production of CH\({}_{4}\) and CO\({}_{2}\) during ruminal fermentation. The inclusion of these essential oils led to a noteworthy reduction in greenhouse gas emissions, specifically CH\({}_{4}\), which is a potent greenhouse gas known to contribute significantly to global warming [44]. In our findings, it was revealed that all doses of essential oils significantly reduced CH\({}_{4}\) production compared to the CON group. This indicates the methane-reducing properties of SAG, PIN, and CLO in ruminal fermentation. Our findings were consistent with the study of [PERSON] et al. [45], which observed a reducing effect of age essential oil on in vitro ruminal methane production. However, a study by [PERSON] and [PERSON] [37] did not find any significant effects of age essential oil on methane production within the rumen. This discrepancy may be attributed to variations in the chemical composition of essential oils and the dose levels implemented in their study. Supporting our observations, [PERSON] et al. [35] reported a decrease in the ruminal production of CH\({}_{4}\) when using pine essential oil, aligning with our findings regarding the reduction in CH\({}_{4}\) production in our PIN treatments. Furthermore, [PERSON] et al. [46] reported a drop in ruminal CH\({}_{4}\) production when clove essential oil was applied, further supporting our findings. These studies offer additional evidence of the methane-mitigating effects of sage, pine, and clove essential oils in ruminal fermentation. Furthermore, our study demonstrated a significant dose-dependent effect of the essential oils on methane production. Specifically, the highest dose of CLO (900 mg/L) led to the lowest CH\({}_{4}\) production, underscoring the remarkable potential efficacy of CLO in effectively mitigating methane emissions. The decrease in methane production observed in our study can be attributed to the bioactive compounds found in these essential oils. These compounds likely inhibit methane-producing microorganisms in the rumen. In their study, [PERSON] and [PERSON] [47] reported that the addition of clove oil, with its antimicrobial properties, significantly reduced ruminal methane production by inhibiting the growth and activity of methanogenic microorganisms. [PERSON] and [PERSON] [48] similarly attributed the reduction in methane emissions to the antimicrobial and antioxidant properties of pine essential oil. They suggested that these properties modulate ruminal fermentation and methane production.  
In addition to the significant decrease in methane production, our study also revealed a substantial reduction in CO\({}_{2}\) production following the addition of essential oils, particularlyin the 900 mg/L CLO treatment. This finding indicates that CLO has the potential to effectively reduce CO\({}_{2}\) emissions as well. The breakdown of cellulose and hemicellulose, major components of ruminant feed, occurs during ruminal fermentation. This breakdown is facilitated by the activity of glucanases, which lead to the production of monomers such as hexoses and pentoses. Following this, the monomers undergo partial oxidation, resulting in the formation of volatile fatty acids. Simultaneously, CO\({}_{2}\) and hydrogen are released [49]. These findings further support the growing body of evidence that highlights the potential of essential oils as natural additives for mitigating greenhouse gas emissions from ruminant animals.