Different inclusion rates of oregano essential oil (OEO) were investigated for their effects on ruminal in vitro fermentation parameters, total gas, methane production, and bacterial communities. Treatments were (1) control, 0 mg/L of OEO (CON); 13 mg/L (OEO1); 52 mg/L (OEO2); 91 mg/L (OEO3); and 130 mg/L (OEO4), each incubated with 150 mL of buffered rumen fluid and 1,200 mg of substrate for 24 h using the Ankom in vitro gas production system (Ankom Technology Corp., Fairport, NY). Treatment responses were statistically analyzed using polynomial contrasts. Digestibility of DM, NDF, and ADF increased quadratically with increasing OEO inclusion rates. Digestibility of DM and NDF were highest for OEO2, whereas ADF digestibility was highest for OEO3, compared with CON, with the remaining treatments being intermediate and similar. Ammonia nitrogen concentrations decreased from CON at a quadratic rate with increasing OEO inclusion rates, and OEO2 had the lowest concentration compared with the other groups. Total VFA, acetate, propionate, butyrate, valerate, and isovalerate concentrations linearly decreased with increasing OEO inclusion rates. Total gas production levels by CON and OEO4 were greater than those of OEO1, OEO2, and OEO3 in a quadratic response, and methane production linearly decreased from CON, compared with OEO4, at a decreasing rate with OEO inclusion rates. As determined by 16S rRNA sequencing, the α biodiversity of ruminal bacteria was similar among OEO inclusion rates. Increasing OEO inclusion rates linearly increased the relative abundance of Prevotella and Dialister bacteria. Several bacteria demonstrated different polynomial responses, whereas several bacteria were similar among increasing OEO inclusion rates. These results suggested that OEO supplementation can modify ruminal fermentation to alter VFA concentrations and reduce methane emissions by extensively altering the ruminal bacterial community, suggesting an optimal feeding rate for future animal studies of approximately 52 mg/L for mature ruminants.

中文翻译：

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牛至精油对体外瘤胃发酵，甲烷生成和瘤胃微生物群落的影响。

研究了牛至精油（OEO）的不同包合率对瘤胃体外发酵参数，总气体，甲烷生成量和细菌群落的影响。治疗方法是（1）对照，0 mg / L OEO（CON）；13 mg / L（OEO1）；52 mg / L（OEO2）；91 mg / L（OEO3）; 分别以150 mg / L（OEO4）和150 mL瘤胃液和1,200 mg底物使用Ankom体外产气系统（Ankom Technology Corp.，Fairport，NY）孵育24小时。使用多项式对比对治疗反应进行统计学分析。DM，NDF和ADF的消化率随着OEO包含率的增加而二次增加。与CON相比，OEO2的DM和NDF消化率最高，而OEO3的ADF消化率最高，其余处理为中等程度和类似处理。氨氮浓度随OEO夹杂率的增加而以二次方的速率降低，而OEO2的浓度最低。VOE，乙酸根，丙酸根，丁酸根，戊酸根和异戊酸根的总浓度随着OEO包含率的增加而线性降低。在二次响应中，CON和OEO4的总产气量高于OEO1，OEO2和OEO3，并且与OEO4相比，CON产生的甲烷产量呈线性下降，随OEO夹杂率的降低而降低。通过16S rRNA测序确定，瘤胃细菌的α生物多样性在OEO包含率之间相似。OEO包含率的增加线性增加了普氏杆菌和迪亚斯特菌的相对丰度。几种细菌表现出不同的多项式响应，而在增加OEO夹杂率中，有几种细菌是相似的。这些结果表明，OEO的补充可以通过广泛改变瘤胃细菌群落来改变瘤胃发酵，从而改变VFA浓度并减少甲烷排放，这为未来的动物研究提供了最佳的饲喂速率，对于成熟的反刍动物，其最佳饲喂速度约为52 mg / L。