Reducing enteric methanogenesis has been an area of focus and significance as methane emissions from cattle contribute to climate change and represent a loss of dietary-derived energy. Methane mitigation strategies have been widely researched, but most are limited in practical value due to associated diminishments in animal performance. One strategy, dietary supplementation of essential oils, has demonstrated variable reductions in enteric methane production in ruminants. The efficacy of using essential oils to reduce enteric methanogenesis likely varies due to inconsistent concentrations of bioactive components. Therefore, it is justified to investigate the effects of these individual bioactive components on methanogenesis and animal performance. Thymol, a terpene and main bioactive component in many essential oils, has effectively reduced methane production in vitro but in vivo data are limited. The objective of this study was to assess thymol fed at levels that correspond with effective in vitro doses on intake and digestion in beef steers consuming forage. This study was approved by the Texas State University IACUC (#8693). The project was a 4×4 Latin Square where four steers were provided one of four levels of thymol (0, 120, 240, and 480 mg thymol/kg forage intake) soaked on alfalfa cubes fed at 20% of the intake from the previous day, and ad libitum hay and water daily. Periods were 28-d with 8-d to adapt steers to treatments, 5-d to measure intake and digestion, 2-d to collect additional samples (i.e., ruminal microbiome and fat tissues), and a 14-d washout period for thymol depletion from the animal system. Diet, refusal, and fecal samples were analyzed for dry matter, organic matter, and fiber. Acid detergent insoluble ash was used to calculate total fecal production for digestibility estimates. Data were analyzed using the MIXED procedure in SAS 9.4. There was no effect of thymol dose on forage OMI (4.61 kg/d ± 0.31; P ≥ 0.48), total OMI (5.65 kg/d ± 0.38; P ≥ 0.44), or total digestible OMI (3.18 kg/d ± 0.18; P ≥ 0.26). Further, organic matter and neutral detergent fiber digestibility were not affected by treatment (56.70% ± 2.81, and 63.04% ± 2.49 respectively; P ≥ 0.14). These data indicate that thymol supplementation at doses that suppress in vitro methane production do not negatively impact intake and digestion in beef cattle. Future project activities include whole genome sequencing of rumen microbial communities to evaluate the impact of thymol on populations, with an emphasis on the methanogen archaea. These data have value for establishing a novel methane-mitigating feed additive to lower the carbon footprint of cattle production without sacrificing performance.

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81 百里香酚对肉牛采食和消化的影响

减少肠道产甲烷作用一直是一个重点领域和重要领域，因为牛的甲烷排放会导致气候变化并代表膳食来源能量的损失。甲烷减排策略已被广泛研究，但由于相关的动物性能下降，大多数策略的实用价值有限。一种策略，即膳食补充精油，已证明反刍动物肠道甲烷的产生有不同程度的减少。由于生物活性成分浓度不一致，使用精油减少肠道产甲烷的功效可能会有所不同。因此，研究这些单独的生物活性成分对产甲烷和动物性能的影响是合理的。百里香酚是一种萜烯，也是许多精油中的主要生物活性成分，在体外可有效减少甲烷的产生，但体内数据有限。本研究的目的是评估百里香酚的饲喂水平，该水平与有效体外剂量相对应，对消耗草料的小牛肉的摄入和消化有影响。这项研究得到了德克萨斯州立大学 IACUC 的批准 (#8693)。该项目是一个 4×4 拉丁方，向四头公牛提供四种水平的百里酚（0、120、240 和 480 毫克百里酚/千克草料摄入量）中的一种，浸泡在苜蓿块上，喂量为前一头牛摄入量的 20%日，每天随意喂干草和水。周期为 28 天，其中 8 天用于使阉牛适应治疗，5 天用于测量摄入量和消化情况，2 天用于收集额外样本（即瘤胃微生物组和脂肪组织），以及 14 天百里酚清洗期动物系统的耗竭。对饮食、拒绝和粪便样本进行干物质、有机物和纤维分析。使用酸性洗涤剂不溶性灰分来计算粪便总产量，以估计消化率。使用 SAS 9.4 中的 MIXED 程序分析数据。百里香酚剂量对饲料 OMI（4.61 kg/d ± 0.31；P ≥ 0.48）、总 OMI（5.65 kg/d ± 0.38；P ≥ 0.44）或总可消化 OMI（3.18 kg/d ± 0.18；P ≥ 0.44）没有影响。 P≥0.26）。此外，有机物和中性洗涤纤维的消化率未受处理影响（分别为56.70%±2.81和63.04%±2.49；P≥0.14）。这些数据表明，以抑制体外甲烷产生的剂量补充百里香酚不会对肉牛的摄入和消化产生负面影响。未来的项目活动包括对瘤胃微生物群落进行全基因组测序，以评估百里香酚对种群的影响，重点是产甲烷古菌。这些数据对于建立一种新型的减少甲烷排放的饲料添加剂具有价值，该添加剂可以在不牺牲性能的情况下降低牛生产的碳足迹。