نوع مقاله : مقاله پژوهشی
عنوان مقاله English
نویسنده English
Introduction: The utilization of natural feed additives to modulate rumen fermentation processes and mitigate enteric methane emissions has garnered considerable attention as a sustainable nutritional strategy in ruminant production systems. Plant-derived essential oils (EOs), with their complex bioactive profiles, offer a promising alternative for shifting the rumen microbial ecosystem toward improved fermentation efficiency. Hyssop (Hyssopus officinalis L.), a perennial herb belonging to the Lamiaceae family, is widely recognized for its medicinal and aromatic properties. The essential oil extracted from this plant contains numerous biologically active components, notably pinocamphone, β-pinene, and various sesquiterpenes, which collectively exhibit potent antimicrobial, antifungal, and antioxidant activities. These multifaceted biological properties suggest substantial potential for optimizing rumen fermentation dynamics and improving nutrient utilization. The present study was therefore designed to systematically evaluate the effects of different inclusion levels of whole Hyssop essential oil (HEO) on in vitro gas production kinetics, methane emission patterns, key fermentation parameters, and microbial indices in ruminal fluid. The central hypothesis was that, due to its antimicrobial properties, HEO could establish an optimal balance between suppressing methane production and maintaining or even improving ruminal fermentation efficiency at a specific concentration. Therefore, this investigation aimed to assess the impact of HEO on ruminal methane output, volatile fatty acid profile, nutrient degradability, and microbial protein synthesis efficiency to identify its optimal dietary inclusion level.
Materials and Methods: The experiment was conducted in a completely randomized design with five treatments and four replicates. Treatments included different levels of HEO (0, 50, 100, 150, and 200 mg/L of culture medium). The essential oil was obtained via hydrodistillation using a Clevenger apparatus from the aerial parts of the plant collected at full flowering. Rumen fluid was collected from three fistulated male sheep (30 ± 3.5 kg body weight) fed a diet consisting of wheat straw and concentrate. The in vitro gas production technique was used, and samples were incubated at 39°C for 96 hours. Gas production was measured at 3, 6, 9, 12, 24, 48, 72, and 96 hours. Methane production was assessed at 24 hours by absorbing carbon dioxide with a 10 M NaOH solution. After 24 hours of incubation, additional fermentation and microbial parameters were evaluated. These post-incubation analyses included measurements of pH, ammonia-nitrogen concentration, total volatile fatty acids (TVFA) concentration, and total protozoal count using a Neubauer chamber. Additionally, degradability of dry matter (DM), organic matter (OM), and neutral detergent fiber (NDF) were determined. Microbial biomass yield and microbial synthesis efficiency were calculated based on truly degraded organic matter and gas production data.
Results and Discussion: The addition of HEO significantly and dose-dependently reduced in vitro methane production. The effect was most pronounced at the highest dose, where methane production decreased by 31% at 200 mg/L compared with the control treatment (P < 0.05). This reduction is likely attributed to the direct inhibitory effect of the HEO bioactive compounds, particularly pinocamphone, on methanogenic archaea and protozoa. Cumulative gas production decreased significantly at all incubation time points compared to the control (P<0.05). Total protozoal population declined linearly with increasing essential oil levels, showing a substantial 33% reduction at 200 mg/L compared to the control (P<0.05), highlighting the strong antiprotozoal activity of the essential oil. TVFA concentration showed a quadratic response (P<0.05), increasing up to the 100 mg/L level and then decreasing at higher doses, indicating a dual stimulatory and inhibitory effect on microbial fermentation. Notably, the 100 mg/L treatment significantly increased microbial biomass yield and microbial synthesis efficiency by 19% and 20%, respectively (P<0.05), indicating a more efficient allocation of digested nutrients to microbial biomass production. Conversely, degradability of DM, OM, and NDF decreased linearly with increasing essential oil levels (P<0.05), reflecting a general inhibitory effect on fibrolytic microbial activity at higher concentrations.
Conclusion: At an inclusion level of 100 mg/L, HEO achieved a significant methane reduction (14.3%) while improving microbial protein synthesis efficiency and maintaining acceptable nutrient digestibility. This specific level of HEO may therefore serve as an effective natural strategy for enhancing the efficiency of rumen fermentation and reducing the environmental impact of ruminant production through lower methane emissions. For practical application, further in vivo trials are recommended to validate these promising in vitro findings and to determine the appropriate dietary inclusion rate.
کلیدواژهها English
Authors retain the copyright. This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0)
