Dietary supplements based on tannin extracts or essential oil compounds (EOC) have been repeatedly reported as a promising feeding strategy to reduce the environmental impact of ruminant husbandry. A previous batch culture screening of various supplements identified selected mixtures with an enhanced potential to mitigate ruminal methane and ammonia formation. Among these, Q-2 (named after quebracho extract and EOC blend 2, composed of carvacrol, thymol, and eugenol) and C-10 (chestnut extract and EOC blend 10, consisting of oregano and thyme essential oils and limonene) have been investigated in detail in the present study with the semi-continuous rumen simulation technique (Rusitec) in three independent runs. For this purpose, Q-2 and C-10, dosed according to the previous study, were compared with a non-supplemented diet (negative control, NC) and with one supplemented with the commercial EOC-based Agolin® Ruminant (positive control, PC). From d 5 to 10 of fermentation incubation liquid was collected and analysed for pH, ammonia, protozoa count, and gas composition. Feed residues were collected for the determination of ruminal degradability. On d 10, samples of incubation liquid were also characterised for bacterial, archaeal and fungal communities by high-throughput sequencing of 16S rRNA and 26S ribosomal large subunit gene amplicons. Regardless of the duration of the fermentation period, Q-2 and C-10 were similarly efficient as PC in mitigating either ammonia (−37% by Q-2, −34% by PC) or methane formation (−12% by C-10, −12% by PC). The PC was also responsible for lower feed degradability and bacterial and fungal richness, whereas Q-2 and C-10 effects, particularly on microbiome diversities, were limited compared to NC. All additives showed the potential to mitigate methane or ammonia formation, or both, in vitro over a period of 10 d. However, several differences occurred between PC and Q-2/C-10, indicating different mechanisms of action. The pronounced defaunation caused by PC and its suggested consequences apparently determined at least part of the mitigant effects. Although the depressive effect on NDF degradability caused by Q-2 and C-10 might partially explain their mitigation properties, their mechanisms of action remain mostly to be elucidated.

中文翻译：

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使用 Rusitec 评估基于单宁和精油混合物的补充剂对瘤胃甲烷和氨形成以及微生物群组成的影响

基于单宁提取物或精油化合物 (EOC) 的膳食补充剂已被多次报道为一种有前景的喂养策略，可减少反刍动物饲养对环境的影响。先前对各种补充剂的批量培养筛选确定了具有增强的减少瘤胃甲烷和氨形成潜力的选定混合物。其中，Q-2（以白坚木提取物和 EOC 混合物 2 命名，由香芹酚、百里香酚和丁子香酚组成）和 C-10（板栗提取物和 EOC 混合物 10，由牛至、百里香精油和柠檬烯组成）进行了研究本研究详细介绍了半连续瘤胃模拟技术 (Rusitec) 的三个独立运行。为此，将根据先前研究剂量的 Q-2 和 C-10 与未补充的饮食（阴性对照，NC）以及补充了基于 EOC 的商业 Agolin® 反刍动物（阳性对照，NC）的饮食进行比较。个人电脑）。从第 5 天到第 10 天，收集发酵培养液并分析 pH、氨、原生动物计数和气体成分。收集饲料残留物用于测定瘤胃降解性。第 10 天，还通过 16S rRNA 和 26S 核糖体大亚基基因扩增子的高通量测序来表征培养液样品的细菌、古菌和真菌群落。无论发酵时间长短，Q-2和C-10在减少氨气（Q-2为-37%，PC为-34%）或甲烷形成（C-12%）方面与PC相似。 10，-12%（PC）。 PC 还导致饲料降解性降低以及细菌和真菌丰富度降低，而 Q-2 和 C-10 的影响（特别是对微生物组多样性的影响）与 NC 相比有限。所有添加剂在体外 10 天的时间内都显示出减少甲烷或氨或两者形成的潜力。然而，PC 和 Q-2/C-10 之间存在一些差异，表明作用机制不同。 PC 造成的明显动物区系丧失及其暗示的后果显然至少决定了部分缓解效果。尽管 Q-2 和 C-10 对 NDF 降解性的抑制作用可能部分解释了它们的缓解特性，但它们的作用机制仍有待阐明。